## 03/13/05

### Questions Welcome!

05:36:09 pm by afshar, Categories: Questions 2

****["Official Afshar Experiment Blog (Questions 2)" FOR NEW POSTS.]****
****[TO SEE OLD POSTS GO TO "Official Afshar Experiment Blog (Questions 1)"]****

Dear friends,
Welcome to my Blog!

But, first please note a few general points:

0) For a brief description of the experiment please visit http://en.wikipedia.org/wiki/Afshar_experiment.
1) I can update my responses mostly during the weekends, so your patience is appreciated.
2) If you are writing a paper on my experiment, you can use http://www.irims.org/quant-ph/030503/ as a permanent reference for my pedagogical paper that contains the experimental details as well as most of the theoretical arguments.
4) This Blog is intended to address well-thought/researched questions related to my experiment. This is not an educational site! If you are not an expert in quantum mechanics (at least through QED) and physical/experimental optics, please ask an expert to take a look at your argument first, and if it is found to be technically rigorous, then by all means submit your question/comment.
5) Scientific objectivity is the direct opposite of irrational emotional ranting. In the interest of scientific methodology, I reserve the right to remove any inappropriate posting.
6) From time to time, I may edit the posts to make sure they are addressed to the correct individual and are at least readable (with all due respect to our non-English speaking friends).
7) The contents of this page are ***COPYRIGHT*** material, and quotations without reference to this source will be vigorously pursued by legal action.

Looking forward to hearing from you.

Shahriar S. Afshar

Comment from: afshar [Member]

You are in [Official Afshar Experiment Blog Questions 2]

Please post your questions here after March 12, 2005. Soon I will organize a comprehensive FAQ page as well.

Thanks!

03/13/05 @ 18:24
Comment from: quantum enforcer [Visitor]

Dear All

I would like some clarification to start this new stream of posts.

Entanglement applies to two or more particles even if one of them is used as input to the two slit experiment, it is not applicable to single particle experiments.

Afshars experiment is conducted in such a manner that it is the setup of the experiment coupled with the conservation of momentum that allows us to know exactly which slit the photon has gone through.

Whilst knowing which way the photon has gone we also manage to show the absense of interference with both slits open via intererence minima.

This is essentially it is it not ?

03/14/05 @ 08:50
Comment from: Quantum Mirror [Visitor]

Dear quantum enforcer

“Whilst knowing which way the photon has gone we also manage to show the absense of interference with both slits open via intererence minima.”

This is a contradiction. Interference minima show the presence of interference, not the absence.

03/14/05 @ 11:24
Comment from: quantum enforcer [Visitor]

Dear Quantum Mirror

By placing wires at the minima of interference we observe when both slits are open the absense of interference is what I mean.

03/14/05 @ 21:17
Comment from: Peter Tanguay [Visitor]

Professor Afshar,

How big could the wires have been and still record sharp complimentarity? What radiant flux criteria would determine detection/nondetection of a minima?

The non destructive measurement of IP, I find as a breakthrough in itself, and possibly capable of many more discoveries.

Peter Tanguay

03/15/05 @ 02:15
Comment from: Quantum Mirror [Visitor]

Dear quantum enforcer

“By placing wires at the minima of interference we observe when both slits are open the absense of interference is what I mean.”

Did I wake up in a new universe when this became page 2? The name of the paper is: “Sharp wave and particle in the same experiment". The only way to show wave is to demonstrate that there “is” interference. There would be no minima without it. Minima show the presence of interference and therefore the wave. At the CCD we detect particles. This is how the experiment shows wave and particle in the same experiment.

Dear Peter Tanguay

“How big could the wires have been and still record sharp complimentarity? What radiant flux criteria would determine detection/nondetection of a minima?”

The size of the wires is not important. The experiment shows that the radiant flux is 80 times higher without interference. This number is more than sufficient to demonstrate interference as necessary for the conclusion that interference is present.

03/15/05 @ 03:51
Comment from: quantum enforcer [Visitor]

Dear Quantum Mirror

Sorry, obviously making a bad impression with my explanation of it. With only one slit open and the wires in place we get scattering of light and a reduction of the image intensity at the CCD. Then by opening the other slit the intensity of the image in restored because the wires are in the minima (almost a complete absense of light) of wave behaviour from two slits. Hence light intenisty is restored due to the wire not in fact blocking any light (or very little).

The CCDs are in addition still recording individual photons and hence “which path information".

Voila, Ware and Particle behaviour simultaneously. Well thats is essentially my understanding of it anyway.

03/15/05 @ 08:25
Comment from: Quantum Mirror [Visitor]

Dear quantum enforcer

I see, you were using the word interference to mean interfering with the photons, not interference in the wave sense. Wrong choice of words in a physics experiment.

03/16/05 @ 05:18
Comment from: Peter Tanguay [Visitor]

Dear Quantum Mirror,

I am not criticizing the size of the wire as too big for detecting a minimum. According to my calculations the present size of the wire influences the cos 2 α term in the Bessel function by only ± 3%. That is the largest difference that is within the accepted limit, for the final value of radiant flux to be considered unaffected. Otherwise stated, δ12 ≈ 0 for the coherent state. I am amazed that the wire could be so big. It spans 143μm with max positioning error, and is 200λ. I believe Afshar has accomplished his goal.

My point for questioning the size of the wire has a different goal. If the wire was at first 100 λ, and then increased to 200 λ, then one would not significantly decrease/increase knowledge of IP minima location. One would also simultaneously double his position knowledge of where the photon could not be. This is because the diameter of the wire is doubled. This simultaneous gaining of knowledge is at the plane of the wires not at the slits. This would violate Hiesenberg, as well as complimentarity. WWI at the plane of the slits is not involved for this question.

Do you see what I am saying? I am also interested in professor Afshar’s input.

Peter Tanguay

03/16/05 @ 08:41
Comment from: Quantum Mirror [Visitor]

Dear Peter Tanguay

I will let prof. afshar have the definitive word on this but the way I see the experiment the wires are only there as a test to show that interference is present. With one slit open you have light sparkling on the wire and a reduced image at the CCD. With both open you have no sparkles and a complete image that compares to the image of one slit without wires. With calculation and trial and error probing we can work out exactly where the minima are located. I don’t see that knowledge of minima location would pertain to complementarity or Heisenberg since with no changes to the equipment they should appear in the same place every time. We would always know that photons were not there.

03/16/05 @ 11:55
Comment from: Uncertainty Identity [Visitor]

To those of you who were suggesting that no previous experiments had simultaneously demonstrated particle and wave behavior, you should examine delayed choice experiments more carefully:

http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm

03/17/05 @ 20:46
Comment from: Quantum Mirror [Visitor]

Dear Uncertainty Identity

The difference is very clear between the two experiments. The name of this experiment is:

“Sharp complementary wave and particle behaviours in the same welcher weg experiment”

In the mentioned quantum erasure experiment they have clearly demonstrated that wave disappears every time they have which-path information. From the article:

Figs. 3 and 4 show the “joint detection” rates R01 and R02 against the x coordinates of detector D0. It is clear we have observed the standard Young’s double-slit interference pattern. . . .

Fig. 5 reports a typical R03 (R04), “joint detection” counting rate between D0 and “which-path” D3 (D4), against the x coordinates of detector D0. An absence of interference is clearly demonstrated. .

This paper clearly has wave and particle in the same experiment.

03/18/05 @ 07:01
Comment from: Quantum Mirror [Visitor]

The last line above should have been which-path and wave in the same experiment.

03/18/05 @ 08:46
Comment from: Quantum Mirror [Visitor]

Dear professor afshar

The pre-print: Attosecond double-slit experiment has arrived:

From the article: Of particular
importance for interpreting quantum mechanics have
been experiments with a single particle at any given time
in the apparatus [5, 6]. More recent work has illuminated
the fundamental importance of complementarity
in which-way experiments [7]

There is of course no reference to this preprint.

Which makes my Questions on 3/8 from this link much more valid.

http://irims.org/blog/index.php/questions/2004/09/25/questions_welcome#c494

Here is my question before from before the preprint was out:

They say the reason for interference in these experiments is because we can’t know which of two peaks created the electron which then self interfered. I think they are reaching a bit too far here. I may be completely off base since I can’t read the paper but could this also be explained as the two peaks created two electrons which interfered with each other? The single peak could only produce one. This sounds more reasonable than we can’t know which peak created the electron so complementarity is put into action. Is there a QM reason this is not possible?

Now we see why the delay in printing this paper is important for physics and Professor afshar. So that papers such as these must explain their results using reasons other than complementarity!

Professor when you have time I would like to hear your opinion of this.

03/22/05 @ 01:55
Comment from: Quantum Mirror [Visitor]

Dear All

New and very important pre-print has just arrived:

http://arxiv.org/PS_cache/quant-ph/pdf/0503/0503201.pdf

From the paper:

Their ingenious gating system allowed GRA to test, perhaps for the first time, quantum mechanical predictions for a single photon state. Interference is confirmed in the obvious way. The which-path predictions are also confirmed; the photon is detected in only one path. What we have shown though, is that a wave model (CIEM) can explain this result. It cannot therefore be concluded that the detection of the photon on one path confirms particle behaviour. In a particle model, the photon takes one path at the beam splitter and is detected in that path, whereas in our wave model the photon splits at the beam splitter, is nonlocally absorbed, and is again detected in only one path. Since the which-path measurement does not confirm particle behaviour, Bohr’s principle of complementarity is
also not confirmed, contrary to what is claimed by GRA. We conclude then, that GRA’s experiments confirm wave behaviour but not particle behaviour, so that complementarity is also not confirmed. We may further add, that if complementary is accepted Wheeler’s delayed choice experiments lead to very strange conclusions: either history is changed at the time of measurement, or history is created at the time of measurement CIEM, on the other hand, explains Wheeler’s delayed-choice experiments in a unique and causal way. It is perhaps fortunate therefore, that complementarity remains experimentally unconfirmed.

03/28/05 @ 01:57
Comment from: Science Nunce [Visitor]

Is this experiment in any evidence that photons which take a definite path could possibly “interfere” with each other?

03/31/05 @ 09:55
Comment from: Quantum Mirror [Visitor]

Dear Science Nunce

I am assuming your question is does this experiment show any evidence that photons which take a definite path interfere with each other?

Yes when they go through a double slit and are resolved by a lens.

04/01/05 @ 02:26
Comment from: Peter Tanguay [Visitor]

Professor,

How did the presentation at the APS conference go? Was there enthusiasm or mostly criticism?

Peter Tanguay

Quantum Mirror,

thank you for the detective work in finding the latest relative preprints. Its great to see the latest relative events on the blog.

Peter

04/01/05 @ 08:46
Comment from: Danko Dimchev Georgiev, MD [Visitor]

http://www.bottomlayer.com/bottom/kim-scully/Image7.gif

http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm

http://www.bottomlayer.com/bottom/kim-scully/Image5.gif

http://www.bottomlayer.com/bottom/kim-scully/kim-sc1.jpg

Dear Prof. Afshar, and dear readers,

I am personally very interested in Delayed Choice experiments and what puzzled me in Afshar’s experiment is NOT the fact that he disproves “complementarity", but the STRONG CLAIM that the focusing lens provides “which way” information. I think the error comes from “misunderstanding” that the lens provides “which way” information, and surely this is not so.

I will post just a brief comment, and I hope that prof. Afshar will realize where his error is. Actually if Complementarity Principle was wrong, then NONE of the Heisenberg relations would be TRUE [for example you cannot measure of a quantum both position and momentum - the uncertainty relation is delta_x delta_p[x] > 1/2 h bar], and the whole quantum mechanics would be destroyed if Afshar’s experiment was true. But there is fundamental error in it :

The lens does not provide “which way” information, because say detector 1 if counts a photon cannot say from which slit the photon passed - actually the photon passes trough both slits, then it interferes with itself and there is interference picture even when when you perform the experiment photon by photon. So photon self-interference IS NOT PROVE against complementarity and this is what is overlooked by Afshar. So my advice is that he withdraws his paper and publishes that his experiment is actually interpreted in the wrong way.

I provide the right argument against his conclusion, but you should read also the paper
“A Delayed Choice Quantum Eraser”
by Yoon-Ho Kim [1], R. Yu, S.P. Kulik, Y.H. Shih, and Marlon O. Scully
http://xxx.lanl.gov/pdf/quant-ph/9903047
Phys.Rev.Lett. 84 1-5 (2000).

and reviewed by Ross Rhodes here:
http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm

The argumentation is clear - the lens does not provide the “which way” information, and two possible pictures are possible - (i) interference or (ii) not interference. Please not the fact that here a single photon can “interfere” or “not interfere with itself” and this depends on whether the “which way” information is available.

But how a 100% of which way information is obtained? Well, this can be done with prism, not with lens !!!!!!!!!!!! Note this, and major consequence at the end of this post.

http://www.bottomlayer.com/bottom/kim-scully/Image7.gif

So now because in the experiment listed above we work with entangled pair of photons, if the “which way” of the second photon is meausred we have “not-self-interference” of the first photon, and if the “which way” of the second is not measured the first photon “self-interferres".

If you read the mentioned paper by Kim et al. (2000) then you will see that lens does not provide “which way” information, and that Afshar is clearly wrong.

MY SUGGESTION IS THAT PROF. AFSHAR PUTS A PRISM TO DETERMINE THE"WHICH WAY” NOT LENS. BUT THEN THE INTERFERENCE PATTERN WILL DISAPPEAR IMMEDIATELY AND I CAN GUARANTEE THAT !!!

If there is not difference between prism and lens on their capacity to provide the “which way” or welcher weg information, then the experiment of Afshar SHOULD HAVE identical results when the lens is substituted with prism.

I hope prof. Afshar will not blame me that I have “cut the wings of the plane", because my critique is clear - he shows that there is “mixing of information” by detectors 1 and 2 about slits A and B and says that this “mixing” is 10^-6, but this is major loophole. There should be ZERO “mixing of information” about the “which way” in order the experiment to be valid, otherwise one can consider that the “mixing value” has increased > 10^-6, and that this increment depends on the experimental setup, and the “mixing” is varying between experiments.

How the photons “understand” the difference between the different systems is another topic and has to to with backward causality as suggested by Wheeler’s delayed choice experiment and Cramer’s interpretation.

CONCLUSION

If there is not difference between prism and lens on their capacity to provide the “which way” or welcher weg information, then the experiment of Afshar SHOULD HAVE identical results when the lens is substituted with prism. But my prediction is absolute failure to observe interference if Afshar put prism “after the grid". Note here that the prism is after the grip, not “before the grid". So the photons will “know” their future !!!

If there is prism after the grid, each photon will not interfere with himself when he passes in the space before the grid, and if there is lens after the grid the photon will interfere with itself in the space before the grid. So actually in the space before the grid the photon will “know the future” - whether there s lens or prism after the grid !!! :-)

At best, perfoeming the prism experiment by Afshar is EASY, and it will prove Complementarity at once, as well as Wheeler’s delayed choice, and will destroy Afshar’s WRONG conclusion.

Best,

Danko Georgiev

04/03/05 @ 12:36
Comment from: Danko Dimchev Georgiev, MD [Visitor]

“Is this experiment in any evidence that photons which take a definite path could possibly “interfere” with each other? “

NO - lens does not provide “which information” so photons interfere and they do not have definite paths.

If they had definite paths then photons cannot interfere, and there would be diffraction from the grid.

If lens is substituted for prism arranged in the way shown by Kim et al. (2000) [web link in my previous post] then photons will have definte paths, but there certainly will be diffraction from the grid.

Sorry to disappoint all readers, but Afshar experiment is interpreted in the wrong way.

I am curious why John G. Cramer took Afshar’s conclusions as evidence for the transactional model, because IF Afshar was wrong then all known interpretations of QM WOULD BE wrong! This is serious overlook by professor like John G. Cramer.

04/04/05 @ 00:17
Comment from: Danko Dimchev Georgiev, MD [Visitor]

Typos:

“not provide “which information” should be red as:
“not provide “which way information”

and

“IF Afshar was wrong then all known interpretations of QM WOULD BE wrong!” should be read as

“IF Afshar was right then all known interpretations of QM WOULD BE wrong!”

Sorry for the typos.

04/04/05 @ 00:19
Comment from: Quantum Mirror [Visitor]

Dear Danko Dimchev Georgiev, MD

Have you read the paper? There is a permanent link at the top of this blog. Prof. afshar has followed the exact QM proof using this lens as Heisenberg. Heisenberg’s microscope proof is based on the imaging theory of a lens, in which the resolution limit of the lens directly enters the uncertainty relation as delta_x, the uncertainty in position. See Physical Principles of the Quantum Theory by Heisenberg or any other textbook on QM for that matter. The paper follows the rules of QM and would not even be under consideration for publication if it did not. Prof afshar has been on a trip to europe to the APS conference and is very busy writing a book and designing the next set of experiments. My answers to this blog are mine alone and are answered to the best of “MY” ability to answer them. I am not associated with Shahriar S. Afshar in any way and don’t hold him accountable to my answers. I am a visitor to this blog just like you and when I answered that the lens resolved the which way information, it was a simple answer to a garbled question. Not in any way meant to replace the paper which Shahriar S. Afshar has written.

04/04/05 @ 03:26
Comment from: Quantum Mirror [Visitor]

Dear Danko Dimchev Georgiev

You say that:"Please not the fact that here a single photon can “interfere” or “not interfere with itself” and this depends on whether the “which way” information is available.”

What is the physical force or mechanism that prevents interference and which way information in the same experiment?

04/04/05 @ 14:24
Comment from: Peter Tanguay [Visitor]

Dear Danko Dimchev Georgiev,

I am also a visitor, however I am a Senior Optical /Laser Engineer for over 20 years. I can assure you that the lens images the pinhole/slit. This is an accepted method to provide which way information .

The photon interfering with itself is, in my opinion, classic double speak by advocates of Copenhagen. They want it both ways. A wave interferes with itself. A photon is a localized event. However in order for CI to be true , they also say the photon has an extended nature. The photon has never been directly obeseved to have an extended nature, that is just what is necessary for the interpretation CI. The photon is only directly observed at detection or emmission. This alone should be enough to say TI is the preferred interpretation.

I beleive the Transactional Interpretation. Because when only waves are present through both slits, there is no need for WWI here, and consequently no conflicts. Most parties beleive TI does not conflict with Afshars results. These parties include the previously mentioned Kastner and John Cramer. I believe Professor Cramer and CIEM proponents advocated this experiment because a wave model is a best fit with the results.

Afshar is foremost an experimentalist, and need not concern himself with interpratation. his conclusions are justified under presently accepted CI theory.

Peter Tanguay

04/05/05 @ 02:34
Comment from: Danko Georgiev [Visitor]

Please note that I am medical doctor, not specialist in mathematics. I think you have not read the essay about the “Delayed choice quantum erasure” that is why my point is not clear. You should look at least the web links [from my previous posts] with the pictures of images from lens and prism!!!

You ask what prevents a photon to interfere with itself, when there is “which way” information. Well, this is a kind of tautology, because “which way” means that you have measured photon travelling in a straight line. If this is the case then there could be no interference [wave-like motion].

Does lens measure “which way"? IF you see the experiment performed by Kim et al. you will see that THIS IS NOT ALWAYS SO!

Lens may measure “which way", but also “may not measure which way” :-) Both type of statistics are seen on Kim et al. experiment. You better read the review of Kim et al. experiment first.

Soon I hope I will be able to write down the mathematics that explains where exactly is the error of Afshar. It will be published online.

Best,

Danko

04/05/05 @ 07:53
Comment from: Danko Georgiev [Visitor]

I have notified him that Afshar interpretation is NOT consistent with delayed choice, and so it seems that the interpretation is against TI. But surely ordinary QM DOES PREDICT no diffraction from the grid, exactly what Afshar has shown. But this is because the lens does not provide which way info. I am curious why prof. Cramer has not spotted the wrong conclusion by Afshar?!

04/05/05 @ 07:58
Comment from: afshar [Member]

Dear Peter,

The APS meeting was very reassuring. Prof. Greenberger (famous in the foundations of physics circles) called the experiment “very beautiful", and said that he would include it in his textbook, if he writes one. He was happy to accept both measurements (sharp interference and which-way) in the same experimental setup. He had a little confusion regarding the quantum erasure aspect of my experiment, which we are hammering out right now…

Dear Dr. Danko Georgiev,

I understand you are excited about your views, and I respect that. But I must say, to put it mildly, you are not “even wrong"! A lens CAN provide which-way information if one observes its image plane. The lens can ALSO provide information on momentum distribution (Fourier transform of the position space) in the Fourier plane, which for a beam of collimated light is the focal plane. The Kim et al. paper uses the Fourier plane to observe one of the photon pairs, so that they can choose a particular wave-front propagation direction. They use a Glen-Thompson prism because it separates orthogonally polarized signal and idler photons produced by the down conversion crystal, not because it acts like a lens!!! …

I do not wish to be blunt, but I’m afraid untill you formally study QM and put your arguments in terms understood by all physicists, I shall refrain from further addressing your posts, in accordance with the conditions announced at the top of this page. To that end, you may find some posts in (Questions 1) page instructive.

Best regards.

04/05/05 @ 09:15
Comment from: Quantum Mirror [Visitor]

“note that I am medical doctor, not specialist in mathematics.”

That is certainly clear.

” I think you have not read the essay about the “Delayed choice quantum erasure” that is why my point is not clear. You should look at least the web links [from my previous posts] with the pictures of images from lens and prism”

Yes the paper was brought to our attention last month and I thoroughly reviewed it and saw no conflict with this paper.

With commentary by Ross Rhodes:
QM predicts that if which-path information is not available at the time of measurement, the pattern will be an interference pattern, as though wave-like photons passed through both slits and “interfered with themselves” to produce the distinctive interference pattern of hits. This is the case at detector D0 at all times.

If you read the “commentary” which is all this web site is, he mentions QM predicts several times. If you read the original paper at this url:

http://xxx.lanl.gov/PS_cache/quant-ph/pdf/9903/9903047.pdf

They don’t say that QM predicts, they say at the first of the paper: Over the years the two-slit interference experiment has been emphasized as a good example of the enforcement
of complementarity.

What you are reading in the commentary is wrong. QM has not made the predictions as he keeps mentioning. complementarity is the predictor. What you are saying is: Complementarity can’t be wrong because complementarity says it can’t be wrong.
This is the same circular logic that has kept complementarity alive all these long years without physical reason or logic.

04/05/05 @ 12:16
Comment from: hugues de chatellus [Visitor]

Dear professor Afshar,

I found your experiment original and interesting and the controversy surrounding it is really an occasion to sharpen our concepts on the nature of light.
I have however a simple comment.
I agree with you when you say that when the grid is removed and one hole (or slit) is closed, the detection enables you to know WWI.
But I think this is not true anymore when you put the grid (and one of the slits is still closed). Because then, what you get in the detection plane, is in a way the Fourier transform of the transmittance function of the grid, that is to say the typical diffraction pattern of a grating (having possibly many orders). So even if the thickness of the wires is small, you have indeed diffraction. This means that a photon detected on detector 2 is likely to come from slit 2, but there is a probability that the photon comes from slit 1. (This probability depends on the relative thickness of the wire that determines the “duty cycle” of the grating) .
So it is unclear to me whether you really get WWI from the experiment with the grid. Could you show us what is seen by the detector 1 in the figure 8 b) ? Because I am pretty sure you have some signal there (even weak) ! This would help !

Thank you very much
Best Regards

04/06/05 @ 03:29
Comment from: quantum enforcer [Visitor]

Dear Hugues de chatellus

As Prof Ashar has stated many times. Due to the conservation of linear momentum the experiment demonstrates that particle to detector is guaranteed to be the way prof Ashar staes it to be.

04/06/05 @ 10:50
Comment from: Quantum Mirror [Visitor]

Dear hugues de chatellus

Fig. 8© on page 33 of the preprint shows the configuration in which both pinholes are open, and the WG is present. The data show that the attenuation of the transmitted light in this case is negligible, R = (-0.1± 0.2)% indicating that the WG has not absorbed or reflected a measurable amount of light within the margin of error, thus establishing the presence of dark fringes at 1 s , so that V=1. It is also evident that the loss of the resolution of the image compared to the decoherent case is negligible. There is a very good agreement between the theoretical value of 0 = Coherent R and the observed value R. This is compelling evidence for the presence of a perfectly visible IP (V=1)

As you see the loss of signal is R=(-0.1± 0.2)%. If the data from the unused CCD were included it would be a small fraction of this amount and as you can see negligible in the outcome of the experiment.

04/06/05 @ 15:22
Comment from: Quantum Mirror [Visitor]

Dear hugues de chatellus

I just realized you were talking about fig. 8b. In this situation the prof. is showing that the wires do cause attenuation and diffraction of the transmitted light. The other detector is not important in this case because we are measuring the amount of diffracted light so he can compare it to fig 8c. and say here is the amount of light diffracted with no interference and here is the amount when interference is present. This is how he proves that interference is present.

04/06/05 @ 15:47
Comment from: afshar [Member]

Dear hugues,

As mentioned in my 12/26/04 @ 16:59 post in (Questions 1) page, you can see from the image plane data in this figure: http://www.physics.ohio-state.edu/~perry/p631/articles/afshar_Slide3.GIF (originally from my seminar at Harvard) that there is indeed a small leak to the “wrong” image region when one pinhole is open. But the situation for the case when both pinholes are open, is not the same as the case in which only one pinhole is open. Remember, you must first add the amplitudes and then square them for an observable. Most people forget this, and carelessly sum up the squared scattered amplitudes from both pinholes, when both are open, which INCORRECTLY leads to the conclusion that the WWI is reduced. If it is done correctly, the sum of the scattered amplitudes from both pinholes cancel out (because they are out of phase by Pi at the wires) and thus never lead to an observable downstream when we square the wavefunctions to get the flux density.

Incidentally, were you one of Sasha’s postdocs at BU? Did you guys talk about this experiment, and if yes, what did Sasha think?

Regards.

04/06/05 @ 18:35
Comment from: hugues de chatellus [Visitor]

Yes, I was one of Sasha’s postdocs at BU, but I left 6 months ago, and I have no idea what he thinks about that.
Bests

Hugues

04/07/05 @ 02:46
Comment from: Quantum Mirror [Visitor]

Dear ALL

Logical analysis of the Bohr Complementarity
Principle in Afshar’s experiment under the
NAFL interpretation

http://arxiv.org/PS_cache/quant-ph/pdf/0504/0504115.pdf

From the paper:

2.1 The Main Postulate of NAFL
If a proposition P is provable/refutable in a consistent NAFL theory
T, then P is true/false with respect to T (henceforth abbreviated as
‘true/false in T’); i.e., a model for T will assign P to be true/false.
If P is undecidable in a consistent NAFL theory T, then the Main
Postulate [5] provides the appropriate truth definition as follows: P
is true/false in T if and only if P is provable/refutable in an interpre-
tation T* of T. Here T* is an axiomatic NAFL theory that, like T,
temporarily resides in the human mind and acts as a ‘truth-maker’
for (a model of) T. The theorems of T* are precisely those propositions
that are assigned ‘true’ in the NAFL model of T, which, unlike
its classical counterpart, is not ‘pre-existing’ and is instantaneously
generated by T*. Note that for a given consistent theory T, T* could
vary in time according to the free will of the human mind that interprets
T; for example, T* could be T+P or T+¬P or just T itself at
different times for a given human mind, or in the context of quantum
mechanics, for a given observer. Further, T* could vary from
one observer to another at any given time; each observer determines
T* by his or her own free will. The essence of the Main Postulate
is that P is true/false in T if and only if it has been axiomatically
declared as true/false by virtue of its provability/refutability in T*.
In the absence of any such axiomatic declarations, i.e., if P is undecidable
in T* (e.g. take T*=T), then P is ‘neither true nor false’ in
T and Proposition 1 shows that consistency of T requires the laws of
the excluded middle and non-contradiction to fail in a non-classical
model for T in which P&¬P is the case

I have never seen such a basket full of horse apples in a single supposed scientific paper. This will be the title of the paper written in reply:

QMBS in a SSSP

Just a little humor in the AM! 8)

04/18/05 @ 01:48
Comment from: R. Srinivasan [Visitor]

Dear Quantum Mirror,
Thank you for inviting comments on my paper. The passage you have quoted has been published in the Int. J. Quant. Info.; see Ref. [4] of my paper. This paper is based on a new logic, NAFL, that was introduced to the physics community in the FQI04 conference noted in Ref. [4]. There were physicists, logicians, philosophers, mathematicians at that conferece. You need to understand what a logic is, before you attempt to judge this work. I suggest that you make the effort to do so. You may find it rewarding.
Regards,
R. S.

04/18/05 @ 03:10
Comment from: Peter Tanguay [Visitor]

Dear Quantum Mirror,

I am not an expert in NAFL, so I cannot say what he is talking about. In a way, I’m glad I dont understand this. I dont think a reviewer will find it easy to decipher either. If only because of this difficulty to decipher, I do not think that the Afshar expeirment will be rejected by this manuscript.

Thanx again for keeping the blog updated

Peter Tanguay

04/18/05 @ 03:18
Comment from: R. Srinivasan [Visitor]

Dear Peter Tanguay,
My paper accepts (or rather, takes for granted) Prof. Afshar’s main experimental conclusions,, namely: (1) The interference pattern is present. (2) Which-way information (WWI) is also present. So it certainly does NOT reject the Afshar experiment; quite the opposite. But despite (1) and (2), Complementarity as I have defined it (and I think, as Bohr intended) is upheld.

The main part of the argument is that the presence of the interference pattern does not PROVE (in a logical sense) that the photon was really’ a wave, i.e., that it really’ exhibited self-interference. The NAFL interpretation of quantum superposition does not ascribe reality to the wave nature of the photon; rather, it only means that WWI was not available to the observer during the times that the superposition held. The interference pattern only indicates that a non-classical probability distribution applied to the photons, still treated as particles. In order to appreciate what quantum superposition means in NAFL, you need to understand the bare essentials of logic and the NAFL truth definition that Quantum Mirror posted (and ridiculed).

In a sense, I am arguing the opposite of Kastner, who would like the wave nature to be `real’ and so rejects that WWI is present in the Afshar expt. In order for Complementarity to be violated in NAFL, one must *simultaneously* demonstrate that the superposed state AND the WWI hold, but this does not happen in the Afshar setup; the WWI only comes later, at time t_2 (see Fig. 1 of my paper) and applies retroactively, whereas the superposed state held prior to t_2. So the WWI does not conflict with the NAFL interpretation of the superposed state, either temporally or in meaning.

I can post a more detailed explanation if necessary. It is not all that difficult to follow what I am saying and I think the explanations I have given in my paper are quite clear. But, you need to set aside preconceived notions/prejudices and take an objective and patient look at my work.
Regards, RS

04/18/05 @ 03:58
Comment from: Quantum Mirror [Visitor]

Dear R. Srinivasan

I think that logic has always been my guide in science and I gravitate toward Quantum Theory because it is the most illogical of all the investigations of science and I want to pull it toward a more logical framework. I think the biggest errors were in the early years of QT and the many years of teaching uncertainty, complementarity and many more aspects QT have caused many errors in logic. I must admit I have not deciphered all of the paper and will make a effort to do so. I do not think the answer to logic in QT will be accomplished by stretching the logic to fit the ideas of current thinking as NAFL seems to do, but to change the earlier errors to a more logical framework. Here is a preprint I like which would change the uncertainty principle and most of CI. I do not think it is complete but brings some logic to QT.

04/18/05 @ 04:13
Comment from: R. Srinivasan [Visitor]

Dear Quantum Mirror,
Thank you for the link. You may well be right that completely new ideas (especially on the nature of light) are needed to bring all of quantum mechanics within a satisfactory logical framework. In fact I have made such a disclaimer in my paper. On the other hand, NAFL already radically departs from many accepted results in conventional mathematics/logic, and may well provide the logical framework for the revolutionary future theories in QM that you have in mind. For example, infinite sets cannot exist in consistent NAFL theories. So how does one justify real analysis in NAFL? My next paper will address this important issue; only then can we think of how to formulate consistent postulates for QM in NAFL. Alternatively, can we do without real numbers? It seems almost inconceivable at the moment, but you may be surpristed to know that at least one prominent quantum physicist (A. Zeilinger) thinks so. He made such an assertion at the FQI04 conference.
Regards, RS

04/18/05 @ 04:35
Comment from: Quantum Mirror [Visitor]

Dear ALL

A fractal entropy dissemination state in complex quantum theory.

After reading much of the paper by R. Srinivasan, it occurred to me that QM as interpreted by NAFL will enter a state of entropy from which it is not possible to make any advances in this field. The confusion that is already inherent in QM combined with the obfuscation and confusion of NAFL means that each paper instead of adding to the knowledge actually adds to the disinformation and confusion.

My question for R. Srinivasan: The universe has been around for at least 12 billion years. The human mind a small fraction of that time. The purpose of Physics is to understand everything in that universe and how it is put together. How do you logically include the mind as a part of quantum physics?

04/19/05 @ 06:55
Comment from: R. Srinivasan [Visitor]

Dear Quantum Mirror,
The obfuscation/confusion is present in interpretations such as, Cramer’s Transactional Interpretation or Many-Worlds. If you are comfortable with “atemporal transactions” and with “confirmation waves” propagating backwards in time or with uncountably many parallel universes, then good luck to you. The NAFL interpretation explains some of the puzzling aspects of QM with unprecedented clarity. But it would be too much of an effort to explain it to you.
Regards, RS

04/19/05 @ 20:49
Comment from: R. Srinivasan [Visitor]

[I an sending this message again as the previous one got truncated for some obscure reason]
Dear Quantum Mirror,
OK, let me try to give a very brief reply to your question. First of all, I claim that the NAFL formulation is a requirement of logical consistency. You should take a look at the proof of Proposition 1 of my paper (for which I have cited earlier references). Secondly, is it clear to you that all truths are pre-existing, independent of the human mind? This is certainly not clear to me. For example, without human beings is it meaningful to talk of the distinction between left/right or east/west, etc.? But leaving aside such deep issues, if you look at my paper carefully, you will see that I am actually supporting the existence of the particle state of the photon as a “reality” independent of the human mind. What depends on the human mind is the probability distribution that one computes for the photons. Thus for t_0

04/19/05 @ 21:42
Comment from: R. Srinivasan [Visitor]

Dear Quantum Mirror,
So the “less than” sign truncates the post. Why? This is more mysterious than quantum mechanics itself. My apologies to Prof. Afshar.

What I was trying to express is the following. The probability distributions depend on the (non-)availability of WWI. If WWI is not available prior to time t_2, then one computes the quantum probability distribution and the interference pattern is seen. In the Afshar Expt., WWI becomes available after time t_2, but this does not “propagate backwards in time” and prevent the superposed state in NAFL. Instead, the WWI can be interpreted to confirm the “reality” of the particle nature of the photon which held all along. The main point is that one does not assign “reality” to the superposed state used to compute quantum probabilities in the NAFL interpretation; instead, the superposed state means that WWI was not available to the observer during those times. It is very important to understand the NAFL truth definition (the Main Postulate, Proposition 1 and its proof) as well as to understand the temporal nature of NAFL truth. These two features of NAFL enable us to make sense of the Afshar Expt. Classically, if WWI becomes available at time t_2, it would prevent the superposition from holding even at earlier times (and hence prevent the interference pattern from appearing), unlike the situation in NAFL.

Quantum Mirror is apparently objecting to the probability distributions depending on the
(non-)availability of WWI to the observer. But probability itself is a paradoxical notion that is observer-dependent even classically (e.g. “conditional” probabilities). So this is not all that surprising to me, though I have no explanation at this point of time on why such a dependency occurs.
Regards, RS

04/19/05 @ 22:53
Comment from: Quantum Mirror [Visitor]

“The obfuscation/confusion is present in interpretations such as, Cramer’s Transactional Interpretation or Many-Worlds. If you are comfortable with “atemporal transactions” and with “confirmation waves”

I would agree with that. I did not mean that all confusion was caused by NAFL. It already seems that you can interpret a experimental result one way and have 10 people see it 10 different ways. I would hate to see it get any worse. I am not at all comfortable with atemporal anything, but experimental results must be explained. Have you seen this preprint on CIEM?

http://arxiv.org/PS_cache/quant-ph/pdf/0503/0503201.pdf

I really like this paper and think it is the most logical I have seen.

” is it clear to you that all truths are pre-existing, independent of the human mind”

I would not say all truths, only the physical truths that built the universe. They did that without our help using energy and lots of time.

04/21/05 @ 08:05
Comment from: Diego Gonzalez [Visitor]

Dr. Afshar –
I am totally an amateur thinker in this realm. However, it has long been my thinking that as regards quantum mechanics and our knowledge of universal principles that there is not “matter” and “energy” as unique entities (or provinces). The idea that matter somehow “converts” to energy and vice versa is probably a product of our effort to understand phenomena. That both states are governed by one set of “rules” only reinforces the likelihood that we are, in fact, always dealing with one ultimate “essence.” Further thinking suggests that the essence is energy.
Recent revelations that so-called particulate energy has characteristics of string tends to support this type of imagery for all energy. When one considers all the known spectra of energy, the similarities of behavior must seem remarkable unless we begin to look at them as variants of the same fundamental essence.
The conclusion I drew was that our measurement tools are quite crude compared to the exquisite nature of the energies we seek to analyze. Suppose energy, released from the gravitational (i.e. energy-bonded) confines, is represented by linked bi-polar modules (something like N-S or +/-) and because of this quantum-like unit polarity extends string-like in rays. Our measuring devices typically rely on intersecting and quantifying the intersected moment. So what we recognize - depending on technique - resembles particles or waves. But it could be neither, as your experiment seems to indicate.
I’m not sure why I write you this, as you seem to have been considering something quite similar already.
Diego Gonzalez

04/21/05 @ 16:19
Comment from: R. Srinivasan [Visitor]

Dear Quantum Mirror,
I looked briefly at the paper
http://arxiv.org/PS_cache/quant-ph/pdf/0503/0503201.pdf
Here is what seems to be the Achilles Heel:

“The CIEM model of the photoelectric effect is of the nonlocal absorption of a photon by a localized atom. The photon prior to absorption may be spread over large regions of space”

In other words, the author seems to be saying that in, say, a beamsplitter, an incident photon splits and passes through both output paths, but is “nonlocally absorbed", at a detector in only one of the paths. The author can do a lot of fancy mathematics to justify this assertion, but it will not have too many takers. In the NAFL interpretation of the beamsplitter expt., the observer did not have WWI prior to the absorption/detection, so the superposed state holds for these times. The superposed state means precisely that the obsever did not have the path information. After the detection, the observer has WWI, and can retroactively assert that the photon passed through only one of the paths, as a particle.

NAFL does not deny that there are truths independent of the human mind. However, the *formal* truths exist only with respect to axiomatic theories and are those that are perceived by the human mind as axiomatic declarations, either directly or via a proof in an axiomatic theory. I claim that this formulation is a requirement of logical consistency, as I had indicated earlier. Truths outside of the primary formalism can be metamathematical (pertaining to semantics, or model theory) or metalogical (i.e., outside of even semantics of NAFL theories).
Regards, RS

04/22/05 @ 00:19
Comment from: Quantum Mirror [Visitor]

Dear All

A new preprint with a very interesting experimental outcome.

“These outcomes (independently confirmed by crossing photon beam experiments in both the optical and the microwave range) apparently rule out the Copenhagen interpretation of the quantum wave, i.e. the probability wave, by admitting an interpretation in terms of the Einstein-de Broglie-Bohm hollow wave for photons. Moreover, this second experiment further supports the interpretation of the hollow wave as a deformation of the Minkowski spacetime geometry.”

http://arxiv.org/ftp/physics/papers/0504/0504166.pdf

THE SHADOW OF LIGHT: LORENTZ INVARIANCE AND
COMPLEMENTARITY PRINCIPLE IN ANOMALOUS PHOTON
BEHAVIOUR

http://xxx.sf.nchc.gov.tw/ftp/physics/papers/0504/0504114.pdf

frpm this paper a mention of the afshar paper I had missed:
Therefore, both corpuscle and wave properties manifest themselves in the same photon system, at the same time, in the same experimental apparatus. Consequently, our experimental results seemingly invalidate Bohr’s principle of complementarity

Let us notice that recently Afshar carried out a double-slit experiment, that
apparently proves a failure of the complementarity principle [10]. He essentially showed that the coherent superposition state, corresponding to the interference pattern, persists
regardless of the fact that the which-way information (trajectory) is obtained in the same
experimental apparatus. Moreover, he states that evidence for coherent wavelike
behaviour is not a single-particle property, but an ensemble (multi-particle) property.
Although the results of ref. [10] do agree with ours, in denying the validity of the wavecourpuscle complementarity, let us stress that Afshar’s experiment is in a sense dual (or complementary) to ours. In fact, in a corpuscle behaviour (trajectory) was observed within a pure wave setting (double-slit interferometer); on the contrary, in our case a wave behaviour (interference) was observed within a pure corpuscular framework.

04/27/05 @ 08:14
Comment from: Danko Georgiev [Visitor]

Dear prof. Afshar,

I have been able to study the mathematics of Fourier optics and I have clearly seen where your error is! You simply ignore the fact that converging lens action is just to convert the spherical frontwaves into plane frontwaves. Actually the image at the Fourier plane is nothing but INTERFERENCE PATTERN. Your error comes from improper comparison of fig.1 and fig.2 in your paper. Well it would be obvious that fig.2 is interference pattern if you have provided the intensity distribution of the higher order maxima surrounding the two Airy discs. The diference between fig.1 and fig.2 is that in the first case the Rayleigh criterion is not satisfied so you have only one central maximum, while in the fig.2. you have splitted with the use of the lens the central maximum into two maxima.

For reference use my paper:
http://philsci-archive.pitt.edu/archive/00002281/

p.s. Responce to your previous commentary: I have not been at all been interested in the Glen-Thompson prisms that separate the pairs of photons, as discussed in Kim et al. 1999. I have just said that the “which way” measurement on idler photon 2 is performed by a prism. So please check again the Kim et al. 1999 paper at ArXiv.org [quant-ph/9903047].

You may ask what is the difference between a prism and a converging lens. Well, the converging lens crosses the light beams coming from the two pinholes so there is interference, while the prism if properly positioned does not cross the light beams.

Well, if one is interested I recommend to check out my PhilSci paper.

Danko Georgiev

04/28/05 @ 04:11
Comment from: Quantum Mirror [Visitor]

Danko Georgiev

Wow, you really worked hard on this paper.

“In contrast Afshar claims to have been able to determine both photon’s path and
momentum in the same experiment thus violating Heisenberg’s uncertainty relations and frankly admits that he is searching for a new physical theory of light.”

There are several mistakes in this tiny sentence alone. (First error)It is which way and wave in the same experiment, not momentum. (second error) it is not HUP but complementarity he is violating. (third error) The idea that he is searching for a new theory of light is patently absurd and made up, as prof afshar has never mentioned such an idea.

“In the July 24, 2004 edition of New Scientist Afshar openly accused the fathers of Quantum
Mechanics to have developed fundamentally wrong theory and suggested that possibly there is no such thing as a photon:”

The New scientist magazine is not a scientific publication. (error 1) one of the first questions on this blog was about QM here is afshar answer:Quantum-Mechanical formalism is completely valid, and should be used to make the calculations for the the amplitudes, as well as the observables in any experiment.(error2) No such thing as a photon? have you gone mad? The photon is mentioned in the paper 19 times. How could he use the photon in the paper and say it does not exist? You are clearly a demented individual to work so hard on a paper with such idiocy involved.(error 3)

“Further, assuming that there is no such thing as a photon Afshar insisted that Einstein’s Nobel Prize for the discovery of the photoelectric effect should be taken back! It is amazing that Afshar takes back with an easy-hand Nobel Prizes:”

The lines you use to validate these outlandish statement are taken out of context and embellished by you.

That is just the tip of the iceberg. You make more errors than I thought humanly possible. The following references are not scientific papers and are as worthless as the entire paper.

Afshar, S.S. (2004). Waving Copenhagen Good-bye: Were the founders of Quantum Mechanics
wrong? Harvard University HEPL, 42 Oxford St., 3rd Fl. Conf. Rm., March 23.

Chown, M. (2004). Quantum Rebel. New Scientist, July 24, No.2457.
Cramer, J.G. (1984). Other Universes II. Alternate View Column AV-03, Analog Science Fiction &
Fact Magazine. http://www.npl.washington.edu/AV/altvw03.html
Cramer, J.G. (2004a). The Blind Men and the Quantum: Adding Vision to the Quantum World. 1st
Hal Clement Memorial Lecture, Boskone 41, Boston, MA, February 15.
http://faculty.washington.edu/jcramer/PowerPoint/Boskone_0402.ppt
Cramer, J.G. (2004b). A Farewell To Copenhagen? Analog - The Alternate View.
http://www.analogsf.com/0410/altview2.shtml
Cramer, J.G. (1998). The Quantum Eraser. Alternate View Column AV-90, Analog Science Fiction
& Fact Magazine. http://www.npl.washington.edu/AV/altvw90.html
39
Cramer, K. (2004). Shahriar S. Afshar: Quantum Rebel.
Dürr, S. & Rempe, G. (2000). Can wave-particle duality be based on the uncertainty relation? Max-
Planck-Institut für Quantenoptik, Progress Report 2001/2002.
http://www.mpq.mpg.de/qdynamics/publications/library/qdynamics02.pdf
Hartle, J.B. (1992). The Space-time Approach To Quantum Mechanics. http://arxiv.org/abs/grqc/
9210004
http://arxiv.org/abs/quant-ph/9903047
Larkin, K.G. & Oldfield, M. (1997a). Fourier Optics: Fraunhofer Diffraction and the 2D Fourier
Transform. http://oldsite.vislab.usyd.edu.au/CP3/Four6/node1.html
Larkin, K.G. & Oldfield, M. (1997b). Fourier Optics: Fraunhofer Diffraction – Exercises.
http://oldsite.vislab.usyd.edu.au/CP3/Four6/node1.html
Melles Griot Inc. (2005). Diffraction. http://www.mellesgriot.com/products/optics/fo_3_1.htm
Rhodes, R (2005). Commentary on “A Delayed Choice Quantum Eraser”. The Reality Program.
http://www.bottomlayer.com/bottom/kim-scully/kim-scully-web.htm
Scully, M.O. & Drühl, K. (1982). Quantum eraser: A proposed photon correlation experiment
concerning observation and ‘delayed choice’ in quantum mechanics. Phys. Rev. A 25: 2208-2213.

04/28/05 @ 06:50
Comment from: Danko Georgiev [Visitor]

Dear Quantum Mirror,

you are very passionate in criticizing me! Well, I am really hard follower of Karl Popper, so I enjoy to be criticized - this will just “test” what I have done i.e. if my work is true it will survive, and if false will be destructed.

Well, you certainly claimed a lot of wrong things.

1. At least in the case of one qubit the complementarity IS manifestation of HUR.
2. If you measure wavelength [lambda] you measure momentum [p] and vice versa. The relation is:
[p]=h/[lambda]
3. What about the “idiotic things” it is not me who claims them but Afshar.

What I have done is to translate the Afshar’s “pompous style” into CLEAR STYLE understandable for everybody.

When he says “welcher weg” this is nothing but claim that uncertainty about position [delta_x] is close to zero i.e. well defined, and when he says “interference” this is nothing but claim that he has measured momentum of the photon, because the interference fringes provide info about the wavelength.

My paper is crystally clear - and it should be even for those who have no idea of QM at all. You cannot have “wave-length” - note the root “wave” if you don’t have uncertainty about position x. If x is certain then the “wave” is gone and there is no “wavelength". Considering that wavelength is linked to the momentum by the above relation, this also means that the momenum is not precisely defined.

My essay is clearly written, so enjoy reading it. If been able to carefully re-think each word used in the abstract, so there is nothing superficial in it.

And as an end - my so-called “translation” of Afshar, is based on mathematical equations, so it is very precise. Note: the equation p = h/lambda has only one constant and two variables linked through this constant, so it resembles really like “dictionary” – “a” means “b” :-) I hope you understood this last joke!

Best,

Danko

04/28/05 @ 09:40
Comment from: Danko Georgiev [Visitor]

A note on the references provided by me

First, Afshar’s paper is just submitted and I doubt that it will ever be published in any good journal.

Second, since Afshar is promoting his work in the web, I am quoting his web postings i.e. I do not have the chance to quote published paper, because it may never be published :-)

Finally, I doubt that a real physicist will need my paper in order to see Afshar’s error, because most professional physicists are far above my level in mathematics and physics.

So, my paper is aimed at those who will start learning QM in the future in order to show them the right sources to do that. And certainly The Optics Project at Department of Physics and Astronomy, Mississippi State University is a good source for begginers.

p.s. If the web courses for begginers quoted by me are for begginers, I am asking myself why Afshar [if he is experienced in the field] is not acquainted with them ?

04/28/05 @ 09:50
Comment from: Mirror Shaker [Visitor]

What are you trying to do, Quantum Mirror? Trying to defend Afshar at any cost? It
is clear from your posts that you don’t even conceive a simple possibility: Afshar is
wrong.

Despite anything you have read on the literature, the converging lens does not
provide which-way information when both pinholes are open. Please, define:

A := “photon passed through pinhole 1″,

B := “photon detected at detector 2″.

I challenge you to prove that P(B | A) = 0 from the general principles of quantum
theory. If this is not the case, there is no which-way determination. Please, you must
try to falsify the assertions of Afshar. After all, what are we discussing here? Science
or Ideology?

04/28/05 @ 11:15
Comment from: Danko Georgiev [Visitor]

Dear Quantum Mirror,

You say: “No such thing as a photon? have you gone mad? The photon is mentioned in the paper 19 times. How could he use the photon in the paper and say it does not exist? You are clearly a demented individual to work so hard on a paper with such idiocy involved”

Well, possibly you have not read the New Scientist paper, or if you did [because obviously you have counted how many time the word “photon” is used] you have not understood Afshar’s position at all. Really the paper is written by Marcus Chown, but indeed he quotes Afshar!

So everything is clear - Afshar says that Einstein’s Nobel Prize should be taken because there is no such thing as photon. Re-read this text again and don’t tell me that I accuse Afshar without reason.

Best,

Danko

04/28/05 @ 11:41
Comment from: afshar [Member]

Dear Danko Georgiev MD,

You have certainly outdone yourself this time! I am sure the copying and pasting of ill-understood concepts and graphics from different sites must have been time consuming, but sadly it shows your complete incompetence in the topic, and it is quite frankly disgraceful. You have certainly overstepped your personal boundaries by statements like: “We suppose that Cramer’s error does not result from ignorance of mathematics but it is due to psychological factors…” I would suggest you have yourself checked for BPD (I’m sure you know what that is Dr.), as you certainly seem to project your own shortcomings unto others!

Just like your telediagnosis, the technical merit of your argument is nonexistent (again due to the fact that you have no idea what you are talking about!) In page 13 of your non-paper you say the lens converts the spherical wavefronts into plane waves. That is true if we use a 1f-1f system as shown in Fig. 10. But in my experiment the lens is placed well beyond 1f from the dual pinholes, and thus produces images in the image plane. Another sign of your lack of understanding of even the basics of the subject matter is the fact that you naively ASSUME that the image plane is the SAME as the focal plane; it certainly IS NOT! If the distance between the lens and the object is more than f (which is the case in my experiment), the image plane falls at a distance always grater than f from the focal plane (which is the Fourier plane if the light illuminating the object is collimated), unless the object itself is placed at infinity, in which case the focal plane and the image plane become the same (due to the fact that light from an infinitely far source is a plane wave)…

This Blog is not an educational site (as outlined at the top of page), but since you seem to be fond of using internet resources, I would suggest you play with the applets in this link: http://webphysics.davidson.edu/applets/Optics/intro.html to get the hang of how a lens works in the geometric limit, and where the focal and image planes are.

To wit, the images in the IMAGE plane (read my paper carefully) provide highly reliable which-way information. [I can’t believe I wasted 15 precious minutes of my life on this nonsense!!!!]

P.S. I am normally not too critical, but you have certainly earned this frank counsel: Please stick to your own profession. There is nothing more embarrassing than a non-specialist making irrelevant remarks in a field well outside his domain.

04/28/05 @ 12:05
Comment from: afshar [Member]

Dear Danko Georgiev MD,

“Afshar says that Einstein’s Nobel Prize should be taken because there is no such thing as photon”

NO! I said, “In order to declare Einstein the winner of the Bohr-Einstein debate, we should take back his Nobel Prize.” That is because Einstein’s idea of a bullet-like photon with straight line trajectory is completely false, and if he kept using the wave model he could have thought of my experiment. That statement is a popularized dramatization aimed at the lay audience of the NS magazine. Obviously, Einstein deserved his Nobel prize; it is just that he should have gotten it for his remarkable Relativity theories rather than his explanation for the photoelectric effect (which has been explained semicalssically by Willis Lamb).

As for “there is no photon” quote, I have expressed my “gut” feeling that ultimately we will find that photons do not exist, but I have made it clear that is my personal opinion, and nothing more. The aim of the experiment has been to rule out Complementarity (which it has successfully achieved), not to rule out photons. Please read the whole article…

04/28/05 @ 12:17
Comment from: afshar [Member]

Dear all,

Afshar Experiment: Einstein’s Rebellion Lives On At Rowan!
Regards.

04/28/05 @ 13:00
Comment from: Danko Georgiev [Visitor]

Dear prof. Afshar,

You say: “Einstein’s idea of a bullet-like photon with straight line trajectory is completely false". NO! whether the photon will move in a straight line or not depends on Principle of Complementarity. In the case of a single qubit this may be seen in HUR. For multiple qubit entangled state the explanation invokes entanglement between the multiple qubit system and the measuring intrument(s) [in general].

Well, I agree that the New scientist paper is too “dramatically written", but even if we ignore it, the problem is still there -

whether there is grid or not, the lens is not measuring the “which way” info.

In order to have “Fourier image” you need INTERFERENCE of information from every elemental aperture of the global aperture pattern [two-slit, three-slit, etc.]. Also I am curious that you have paid little attention to the popularization of the HOLOGRAPHY, and explanation of holograms as Fourier transformed images.

Danko

04/28/05 @ 13:20
Comment from: afshar [Member]

Dear Danko Georgiev,

EVRY image is produced by the self-interference of the diverging parts of the same wavefunction originating from a point source on the object. In my experiment we have two such sources. i.e. the two pinholes. But in the image plane, the two separated wavefuntions do not overlap, and thus cannot produce a spatial interference pattern, as evidenced by the two individual spots. Do you now understand the difference between the image plane and the focal plane? BTW/ contraty to your assertion, my images beat the Raleigh crtierion handsomely (that is if you really understand the criterion)!

“whether there is grid or not, the lens is not measuring the “which way” info. “

Then you are saying Heisenberg’s Microscope proof of the uncertainty principle is wrong! Good luck proving that…

04/28/05 @ 13:30
Comment from: Quantum Mirror [Visitor]

Danko Georgiev

Karl Popper, you don’t even belong on the same planet as he does. He is the father of the scientific positivism and you are the Weekly World News scavenger.

“Well, possibly you have not read the New Scientist paper”

The New Scientist magazine is not a scientific paper. If one could use popular magazine and web site articles to argue science, anyone could destroy relativity, evolution, Bohr, quantum mechanics or any theory. There would be no science.

You must admit that you collected all the garbage you could find and twisted it to the worst possible conclusion in anger over the reply you received from afshar. You could not possibly understand QM or the scientific method to make such idiotic conclusions based on such unreliable source material. I am certainly glad you are not my medical doctor. I would hide all the Good Housekeeping and Ladies Home Journal medical articles in your waiting room.

04/28/05 @ 14:05
Comment from: R. Srinivasan [Visitor]

Dear Prof. Afshar,
In your recent posts to Danko Georgiev, you make the following assertions:

(1) “To wit, the images in the IMAGE plane (read my paper carefully) provide highly reliable which-way information".
(2) “That is because Einstein’s idea of a bullet-like photon with straight line trajectory is completely false, and if he kept using the wave model he could have thought of my experiment.”

From (2), it would appear that you would conclude the wave nature of the photon from the existence of the interference pattern in your experiment; i.e., you would conclude that the photon “really” passed through both slits, as a wave. How do you reconcile this assertion with (1), which would indicate that you believe the which-way information to be “reliable", which in turn means that you believe that the photon “really” passed through only one slit? Or are you assuming something like the CIEM model [quant-ph/0503201] of Kaloyerou to reconcile the which-way information with a wave model? Or are you viewing this as a paradox which cannot be explained using existing theories?
Regards, RS

04/29/05 @ 04:13
Comment from: afshar [Member]

Dear R. Srinivasan,

“Or are you viewing this as a paradox which cannot be explained using existing theories?”

I would LEAN towards this option, but that is purely a personal preference and nothing more.

Regards.

04/29/05 @ 05:09
Comment from: Quantum Mirror [Visitor]

Dear prof afshar
I really am one to jump on a bandwagon for a while if I find something that fits, but that is just my nature. :) I can jump off very quickly also as I am quite flexible. I am on this bandwagon now:

http://arxiv.org/ftp/physics/papers/0504/0504166.pdf

In this paper when you have time to read it, the author explains interference as deformation of the Minkowski space-time geometry by breakdown of local Lorentz invariance. This would be a incredible breakthrough which could unite relativity with quantum theory. I was wondering if you had read this and your thoughts on it. It is all based on experimental results.

04/29/05 @ 06:35
Comment from: afshar [Member]

Dear QM,

It looks very intereting. I’ll read up on it next week, and thanks for the heads up!

Regards.

04/29/05 @ 07:58
Comment from: Danko Georgiev [Visitor]

Dear prof. Afshar,

I will “close my eyes” for the fact you have personal attitude to my personality, not to my critique. Now straight to the topic:

You simply do not understand what the Fourier transform is, so I will clarify the issue using the exact values [data] from your experimental setup. I have been able to use the online calculator of the Rayleigh criterion at:

in order to verify that your results are not manipulated. What is good is that you really have provided true results and I express my regards for providing all details about your setup in the IRIMS paper.

So now I will show you that I am very well acquainted with the action of the converging lens and that I do make distinction about the focal and image planes. However I didnot consider that the details of so great importance for my PhilSci paper - they are obvious.

Let me first list some relevant info from your setup:
photon wavelength - lambda = 650 nm;
distance between pinholes - d = 2 mm;
pinhole (aperture) diameter - a = 0.25 mm.

1. Using the Rayleigh criterion you may easily see that the Airy disc of each pinhole “grows” along the optical axis. At distance up to ~0.5 meters the two Airy discs have not yet significantly interfered with light coming from the other pinhole.

2. You first put screen sigma_1 at distance L from the double-pinhole L = 4 m. So at this distance the double-slit pattern is clearly seen. Also at this place the image is essentially Fraunhofer diffraction image - i.e. the wavefronts can be approximated as plane ones - the usual criterion is d

04/29/05 @ 10:59
Comment from: Danko Georgiev [Visitor]

2. You first put screen sigma_1 at distance L from the double-pinhole L = 4 m. So at this distance the double-slit pattern is clearly seen. Also at this place the image is essentially Fraunhofer diffraction image - i.e. the wavefronts can be approximated as plane ones - the usual criterion is d

04/29/05 @ 11:00
Comment from: Danko Georgiev [Visitor]

Dear prof. Afshar,

I will “close my eyes” for the fact you have personal attitude to my personality, not to my critique. Now straight to the topic:

You simply do not understand what the Fourier transform is, so I will clarify the issue using the exact values [data] from your experimental setup. I have been able to use the online calculator of the Rayleigh criterion at:

in order to verify that your results are not manipulated. What is good is that you really have provided true results and I express my regards for providing all details about your setup in the IRIMS paper.

So now I will show you that I am very well acquainted with the action of the converging lens and that I do make distinction about the focal and image planes. However I didnot consider that the details of so great importance for my PhilSci paper - they are obvious.

Let me first list some relevant info from your setup:
photon wavelength - lambda = 650 nm;
distance between pinholes - d = 2 mm;
pinhole (aperture) diameter - a = 0.25 mm.

1. Using the Rayleigh criterion you may easily see that the Airy disc of each pinhole “grows” along the optical axis. At distance up to ~0.5 meters the two Airy discs have not yet significantly interfered with light coming from the other pinhole.

2. You first put screen sigma_1 at distance L from the double-pinhole L = 4 m. So at this distance the double-slit pattern is clearly seen. Also at this place the image is essentially Fraunhofer diffraction image - i.e. the wavefronts can be approximated as plane ones - the usual criterion is d

04/29/05 @ 11:01
Comment from: Danko Georgiev [Visitor]

Dear prof. Afshar,

I will “close my eyes” for the fact you have personal attitude to my personality, not to my critique. Now straight to the topic:

You simply do not understand what the Fourier transform is, so I will clarify the issue using the exact values [data] from your experimental setup. I have been able to use the online calculator of the Rayleigh criterion at:

in order to verify that your results are not manipulated. What is good is that you really have provided true results and I express my regards for providing all details about your setup in the IRIMS paper.

So now I will show you that I am very well acquainted with the action of the converging lens and that I do make distinction about the focal and image planes. However I didnot consider that the details of so great importance for my PhilSci paper - they are obvious.

Let me first list some relevant info from your setup:
photon wavelength - lambda = 650 nm;
distance between pinholes - d = 2 mm;
pinhole (aperture) diameter - a = 0.25 mm.

1. Using the Rayleigh criterion you may easily see that the Airy disc of each pinhole “grows” along the optical axis. At distance up to ~0.5 meters the two Airy discs have not yet significantly interfered with light coming from the other pinhole.

2. You first put screen sigma_1 at distance L from the double-pinhole L = 4 m. So at this distance the double-slit pattern is clearly seen. Also at this place the image is essentially Fraunhofer diffraction image - i.e. the wavefronts can be approximated as plane ones - the usual criterion is d

04/29/05 @ 11:02
Comment from: Danko Georgiev [Visitor]

Dear all,

sorry for this unsuccessful “pasting” of my Wikipedia response. Just check out the full version at:

http://en.wikipedia.org/wiki/Talk:Afshar_experiment

There is step-by-step analysis of the whole setup using data from the IRIMS pre-print.

Regards,

Danko

04/29/05 @ 11:06
Comment from: Danko Georgiev [Visitor]

Dear R. Srinivasan,

Your remark is valid if you first say that there is [1]interference pattern and then you prove [2] that there is “which way” info. Going from 1 to 2 is ridiculous!

While Afshar first points out [2] then he goes to [1]. Now “as if” the situation implies paradox, because [2] is the “true” assumption from where you have started. Well, the problem is that [2] is false.

Danko

04/29/05 @ 11:11
Comment from: Mirror Shaker [Visitor]

To Prof. Afshar:

This in line with Srinivasan thought. Forget Complementarity for a moment. It seems
that your experiment cannot be explained by the standard quantum theory. If you
know for each photon the slit through which it passed. In this case the quantum
recipe is to sum the probabilities and not the amplitudes for each alternative. In this
way there could be no interference, and your wires should be absorbing some of the
photons. Please, if you forget that private philosophy of Bohr called
Complementarity which was never really used by any working physicist, how do you
apply the standard quantum formalism to describe your experimental result:
which-way + interference?

After all, the quantum recipe is “add the amplitudes for each alternative when you
don’t have any way to know that a single alternative happened at a time, otherwise
add the probabilities for each alternative". Since in your experiment you know
which-way each photon went, then you know that a single alternative happened before
each detection. So, add the probabilities, forget interference and standard quantum
theory can’t explain your result of zero absorption at the wires.

Could you give me some light ;-) on that?

Regards.

04/29/05 @ 15:02
Comment from: Quantum Mirror [Visitor]

Danko Georgiev

The Rayleigh criterion is a formula for figuring the resolving power of telescopes or lens systems. The formula is to figure how close two light sources can be together and the size of the lens needed to resolve detail. The minima and maxima in a pinhole are the brighter and darker circular lines caused by diffraction. This is not the same as the minima/ maxima of two slit or two pinhole interference pattern.The Rayleigh criteria is not a criteria for double slit interference. In fact has nothing to do with spatial relations of interference. You should really have an expert in quantum mechanics and physical/experimental optics look at your work before you post it all over the web. You are quick to study and make judgments but the devil is in the details.

04/29/05 @ 17:17
Comment from: Danko Georgiev [Visitor]

Dear QM,

The Rayleigh formula is formula, so you can change the variables. If you use this formula and change distance from the pinhole, you will see that the Airy disc will “grow” as it goes away from the slit - this is so because the angle theta from the normal where the first minimum occurs is CONSTANT(!) because sin theta is constant.

I have also said that Fraunhofer diffraction [Rayleigh formula is assuming far-field approximation] is just SPECIAL CASE of Fresnel diffraction. Nevertheless you can stil use Rayleigh formula to roughly approximate the distance from the two pinholes from where you start to observe the Fraunhofer image.

note: exactly the Fraunhofer pattern is the POPULAR ONE, and you should know that before certain distance L from the screen you DON’T have such pattern. The limit case is to put the detector film just behind the two pinholes - you will get 2 discs simply because there is no enough space for the Airy discs to “grow” and interfere.

You are the one who should read some maths.

Danko

04/29/05 @ 22:22
Comment from: Danko Georgiev [Visitor]

comment on “change the variables". The meaning is that Rayleigh formula is parametric one, so in order to built a function of only variables x and y, you should fix some of the parameters. E.g. you can fix photon’s wavelegth, and lend D and then you investigate the relation between distance L and spatial size of the Airy disc. With different “fixations” of the parameters, you choose which will be contants, and which will be free variables.

04/29/05 @ 22:27
Comment from: Quantum Mirror [Visitor]

Danko Georgiev

Keep spewing garbage idiot. Are you still at the Medical University Of Varna. I think they should be advised of your idiocy and what a fool you are making of yourself. You do not know the difference in the Rayleigh Criterion and the Rayleigh formula? The Rayleigh formula was thrown out by the plank formula in 1900. The Rayleigh Criterion is exactly what I said it is. You should learn to read and understand. I see why most of your papers were removed from Arxiv and never accepted for publication. You are the biggest FOOL I have ever had to deal with and as such I will no longer reply to your ludicrous statements. As you can tell afshar is no longer wasting his time.

04/30/05 @ 05:21
Comment from: Danko Georgiev [Visitor]

Dear QM,

I like your style! The expression “keep spewing garbage idiot” is really very funny, at least for me, maybe because English is not my mother language. Well, maybe I was amazed because I had to look in the dictionary for the meaning. There I have found a bunch of possible translations so I thought: “Wow, what I compression of information - just 4 words - but their meaning is enough to fill half a page :-)”

Danko

04/30/05 @ 07:32
Comment from: afshar [Member]

Dear All,

Below is an exchange between Bill Unruh (a veteran physicist) and Danko Georgiev (AKA The Fake) in which Bill rejects his utter nonsense. Although Bill disagrees with me, I applaud his defense of truth, which in this case happens to be the defense of my arguments. The likes of Georgiev MUST be rejected and marginalized by all real scientists in the interest of scientific advancement, all personal differences aside. I have no problem with considering unorthodox ideas (after all some may consider me as such,) but after one realizes an individual is fake, and it takes no more than a couple of exchanges for a pro., the individual must be warned, and if stubborn, BANNED from professional forums. Therefore, I shall have Danko Georgiev banned from this site, and will make recommendations to PhilSci and arXiv archives, as well as Wikipedia to put his name on their blacklist. I would also encourage you to do so. Sorry Danko, you brought this unto yourself after my repeated warnings…

—————————
[From: http://en.wikipedia.org/wiki/Talk:Afshar_experiment]

Here is the question posed by Unruh. He asks “Yes, the lens acts as a “Fourier transform” device, but again so what?”

From: Bill Unruh mailto:unruh@physics.ubc.ca Sent: Friday, April 29, 2005 1:33 PM To: Danko Georgiev

Again, your interpretation I agree makes no sense. The “which way” infomation IS there in the images, just as it is there in the original pinholes. I would certainly not advise him to give you the $1000 based on this argument. While he is wrong, he is not wrong in the way you have outlined it. The fact that IF you were to place a screen before the lens, you would see an interference pattern, is irrelevant to whether or not the photons falling on the detectors convey “which way ” information. Yes there is a Airy disk. but so what. Yes, the lens acts as a “Fourier transform” device, but again so what. The natural propagation of the light also acts as a fourier transform. And the lens can be set up to compensage for the natural propagation transform to give you back the original image. Bill Unruh ————- My [Danko Georgiev] reply is: Dear Bill, You simply don’t understand the essence of my argument. The existence of light “wave” implies that there is no “which way". What I have shown is that application of F . F^-1 returns the SAME image at the focal lens plane as one can expect from “classical straight ray” optics. So IF you cannot decide whether you have F . F^-1 or “clasical straight ray image” THEN THERE IS NO WHICH WAY INFO! Also I can show you that indeed F. F^-1 existence NEEDS “wave interference” and also I CAN PROVE that the actual implication of F . F^-1 is seen in Afshar experiment, because the image plane is 0.38 m behind the focal plane, so I expect higher order diffraction maxima, while the “classical scenario” CANNOT predict these outer maxima, but just expects enlargement of the central Airy discs. Cheers, Danko ——————————- [From e-mail CCed to me by Bill] [Bill Unruh] Since you decided to post an answer to a private reply to you to this whole list, I will respond in the same way. a) EM waves are linear. Thus the image at the detectors is precisely the sum of the images from the waves emitted at the two slits. Those independent images are that if the wave came from pinhole 1, the image (yes, with diffraction pattern) falls entirely on detector 1, and the image from pinehole 2 falls entirely on detector 2. This is an elementary result of fourier optics. Yes, there is interference in the intermediate region, interference which comes from precisely the linearity of the waves, but that is irrelevant. On the basis of your fourier optics, the Green’s function of the EM field is precisely such that the image at detector 1 depends only and solely on the amplitude at slit 1, and that at detector 2 depends only and solely on that at slit 2. b) What has “classical straight ray” arguments got to do with anything. Who discusses them but you? The argument is not based on “classical straight ray” arguments. It is based on the wave nature of light throughout. You may be getting confused when the term “which way” is used. It is NOT which way the photon went between the slit and the detector. That is NOT what “which way” refers to. It refers to whether or not the photon came through slit 1 or slit 2. That is all. It has nothing to do with what the photon did in the space between the slits and the detectors. You may have gotten misled by the use of the word “way” in “which way” and thought that it referred to a complete path. It does not. In this context it would better be phrased as “which slit". It is ONLY which slit the light came out of that is being determined, not anything about how it travelled between the slit and the detector. 04/30/05 @ 08:33 Comment from: Mirror Shaker [Visitor] Dear Afshar, Have you seen my post above? Regards. 04/30/05 @ 09:15 Comment from: Mirror Shaker [Visitor] I have been studying quantum mechanics very hard using many books but to me none is so clear and convincing as the third volume of Feynman Lectures on Physics. There I can read the following in the Summary of page 1-10. (1) The probability of an event in an ideal experiment is given by the square of the absolute value of a complex number \phi which is called the probability amplitude: P = probability, \phi = probability amplitude, P = | \phi |^2. (2) When an event can occur in several alternative ways, the probability amplitude for the event is the sum of the probability amplitudes for each way considered separately. There is interference: \phi = \phi_1 + \phi_2, P = | \phi_1 + \phi_2 |^2. (3) If an experiment is performed which is capable of determining whether one or another alternative is actually taken, the probability of the event is the sum of the probabilities for each alternative. The interference is lost: P =P_1 + P_2. Now, I have a homework problem to solve. It is a calculation related to the Afshar experiment. But I am really at lost here: it is currently accepted that the converging lens allows me to know for each detected photon the slit which it passed through. So, following Feynman I think that the right thing is to use rule (3) and add the probabilities for each alternative, and not the amplitudes. But if I do so there could be no interference in this experiment and I could not explain how do the photons manage to pass the wires without getting absorbed. A few possibilities come to my mind: (a) The converging lens does not really tells which slit each photon passed through. But how can I prove, by theory or experiment, that a photon coming form slit 1 can be detected at detector 2? Or how can I prove that this cannot happen? (b) Maybe the problem is with the meaning of the word event in this case. I notice that “photon absorbed by one of the wires” and “photon detected by one of the detectors” are events that happen at different regions of the apparatus. And I also notice that in the interference region there is no way to know which slit each photon passed. To make things even worse, the way we “watch” the photons in the interference region is very different from what is normally understood by a measurement in quantum mechanics: we know that each photon is interfering with itself because we don’t find them at the wires; it is a sort of measurement that doesn’t disturb the photons. Now we are watching and not disturbing. © Feynman is wrong. And the rules of quantum mechanics should be revised. I would greatly appreciate any help with my homework question. Thank you all. 04/30/05 @ 10:00 Comment from: Mirror Shaker [Visitor] I have been studying quantum mechanics very hard using many books but to me none is so clear and convincing as the third volume of Feynman Lectures on Physics. There I can read the following in the Summary of page 1-10. (1) The probability of an event in an ideal experiment is given by the square of the absolute value of a complex number \phi which is called the probability amplitude: P = probability, \phi = probability amplitude, P = | \phi |^2. (2) When an event can occur in several alternative ways, the probability amplitude for the event is the sum of the probability amplitudes for each way considered separately. There is interference: \phi = \phi_1 + \phi_2, P = | \phi_1 + \phi_2 |^2. (3) If an experiment is performed which is capable of determining whether one or another alternative is actually taken, the probability of the event is the sum of the probabilities for each alternative. The interference is lost: P =P_1 + P_2. Now, I have a homework problem to solve. It is a calculation related to the Afshar experiment. But I am really at lost here: it is currently accepted that the converging lens allows me to know for each detected photon the slit which it passed through. So, following Feynman I think that the right thing is to use rule (3) and add the probabilities for each alternative, and not the amplitudes. But if I do so there could be no interference in this experiment and I could not explain how do the photons manage to pass the wires without getting absorbed. A few possibilities come to my mind: (a) The converging lens does not really tells which slit each photon passed through. But how can I prove, by theory or experiment, that a photon coming form slit 1 can be detected at detector 2? Or how can I prove that this cannot happen? (b) Maybe the problem is with the meaning of the word event in this case. I notice that “photon absorbed by one of the wires” and “photon detected by one of the detectors” are events that happen at different regions of the apparatus. And I also notice that in the interference region there is no way to know which slit each photon passed. To make things even worse, the way we “watch” the photons in the interference region is very different from what is normally understood by a measurement in quantum mechanics: we know that each photon is interfering with itself because we don’t find them at the wires; it is a sort of measurement that doesn’t disturb the photons. Now we are watching and not disturbing. © Feynman is wrong. And the rules of quantum mechanics should be revised. I would greatly appreciate any help with my homework question. Thank you all. 04/30/05 @ 10:02 Comment from: Mirror Shaker [Visitor] I have been studying quantum mechanics very hard using many books but to me none is so clear and convincing as the third volume of Feynman Lectures on Physics. There I can read the following in the Summary of page 1-10. (1) The probability of an event in an ideal experiment is given by the square of the absolute value of a complex number \phi which is called the probability amplitude: P = probability, \phi = probability amplitude, P = | \phi |^2. (2) When an event can occur in several alternative ways, the probability amplitude for the event is the sum of the probability amplitudes for each way considered separately. There is interference: \phi = \phi_1 + \phi_2, P = | \phi_1 + \phi_2 |^2. (3) If an experiment is performed which is capable of determining whether one or another alternative is actually taken, the probability of the event is the sum of the probabilities for each alternative. The interference is lost: P =P_1 + P_2. Now, I have a homework problem to solve. It is a calculation related to the Afshar experiment. But I am really at lost here: it is currently accepted that the converging lens allows me to know for each detected photon the slit which it passed through. So, following Feynman I think that the right thing is to use rule (3) and add the probabilities for each alternative, and not the amplitudes. But if I do so there could be no interference in this experiment and I could not explain how do the photons manage to pass the wires without getting absorbed. A few possibilities come to my mind: (a) The converging lens does not really tells which slit each photon passed through. But how can I prove, by theory or experiment, that a photon coming form slit 1 can be detected at detector 2? Or how can I prove that this cannot happen? (b) Maybe the problem is with the meaning of the word event in this case. I notice that “photon absorbed by one of the wires” and “photon detected by one of the detectors” are events that happen at different regions of the apparatus. And I also notice that in the interference region there is no way to know which slit each photon passed. To make things even worse, the way we “watch” the photons in the interference region is very different from what is normally understood by a measurement in quantum mechanics: we know that each photon is interfering with itself because we don’t find them at the wires; it is a sort of measurement that doesn’t disturb the photons. Now we are watching and not disturbing. © Feynman is wrong. And the rules of quantum mechanics should be revised. I would greatly appreciate any help with my homework question. Thank you all. 04/30/05 @ 10:04 Comment from: Quantum Mirror [Visitor] Dear Mirror Shaker I think the hardest thing for beginning physics students to realize is some of their textbooks are 30 to 50 years behind the current thinking in physics. The books are a good solid basis for education and a must for learning physics. The up to date physics is different because experiments, new mathematics and theories are constantly changing. The experiments must be our logical and moral guide to what nature is trying to tell us. If you read the paper that afshar has written he clearly states that QM formalism can be used to break only the “strict” sharp measurements of complementarity. Where 0 less than V less than 1 and the same for K are “NOT” covered in this paper at all. Bohr’s strict “NEVER” has been violated and it is up to the physicist at the leading edge of theory and up to date on the latest papers to explain why. You must follow your textbooks but also go and find some of the more recent papers on the subject you are studying and try to follow them through their references back to where the textbook left off. I hope this answers your question and you realize that I am not defending Afshar at all cost. A good well written logical argument will turn me and I am sure afshar immediately to the other side. Most of the arguments posted here have already been covered, make no sense or are for conditions of V and K in between sharp measurements. good day to you! 05/01/05 @ 06:59 Comment from: Mirror Shaker [Visitor] Dear Quantum Mirror. Thank you very much for your answer. I am going to read Afshar’s paper in greater detail again and keep thinking about it. I must confess that to me K = 1 and the use of a superposition of wave-functions in the calculations (instead of a density matrix representing a statistical mixture in the sense of von Neuman) seem to contradict Feynman’s rules (2) and (3). I understand that I should not expect that every textbook assertion should be taken blindly as the right way to interpret and do things in a real experiment, but I still feel that this experiment is going to tell us more than the violation of Bohr’s complementarity. Is it possible for Afshar to place a comment? 05/01/05 @ 15:45 Comment from: Peter Tanguay [Visitor] Dear Afshar, The reflectivity for the coherent case was observed to be (-0.1 +/- 0.2)% pg 17 of the preprint. For my own research I have two technical questions. what would the reflectivity criteria be for observation/ non observation of a minimum. Is it a delta between R coherence and Decoherence? Is it a % value for R cohorence? I am curious as to how big the wires could be before you would no longer see sharp complimentarity and V is less than 1. you may review my physics publications regarding the transaction interpretation if you are so inclined. They are on my business website. www.petertanguay.com PS you were more patient than I , regarding Danko . Dear Quantum Mirror, I can understand your your skepticism regarding TI confirmation waves. It is not a concept one should just accept. I ask you to read John Cramers Transactional interpretation of Quantum mechanics chapter 3 page 2. I beleive it is logical to consider them, as advanced waves are solutions of the electromagnetic equation. They are not just dreamed up. Feynman considered them for explaining electron recoil, albiet unsuccessfully. In addition, Dirac developed a time symmetric formalism . once again thanx for keeping the blog up to date with your research. I generally review the articles you post. My own published manuscript is on my business web site. www.petertanguay.com Peter Tanguay 05/02/05 @ 02:57 Comment from: Quantum Mirror [Visitor] Dear Peter Tanguay The way I see it the wire size would be optimal at the size below where image reduction starts to escalate. The wires are only being used to show that interference is present so does not play into the calculation for sharp complementarity. If interference is present it is a 1, if not it is a 0 so in essence it is like a switch either on or off. “I can understand your your skepticism regarding TI confirmation waves.” Where did you get this idea? I don’t believe i have ever said one way or another if I agreed with TI. I have a little trouble with the conservation of energy over time, but if it explains enough quantum mysteries and a good experiment can verify it someday I will be on board immediately. Hope this helps! 05/02/05 @ 12:54 Comment from: Peter Tanguay [Visitor] Dear Quantum Mirror, I see also that V= 0 or V=1 . In Afshar preprint page 19 , he sets the lower limit criteria for the wire as; e is much greater than lamba for opacity , while reducing the size of the wire as much as possible. It is also stated (bottom pag 18) that the WG has not absorbed or reflected a measureable amount of light within the margin of error. I guess my questions are: what is the margin of error? What is a meaurable amount of light? Ultimately, what size wire would fail to measure a minima? In the experiment R = ( -.1 +/- .2) % This is common sense correct as it straddles zero. So I donot disagree with the results. I would like to further define /quantify them. On the side, I got the impression that you did not find TI logical in your previous post where you appear to agree with the obfuscation / confusion of TI and confirmation waves. I may have misunderstood this post. Glad to hear that logic prevails. Peter Tanguay 05/03/05 @ 04:04 Comment from: quantum enforcer [Visitor] Dear Prof Afshar Surely the quantum community has analysed this experiment by now and either verified or falsified it by now ? Then we can move on as to what it all means to show wave particle duality simultaneously perhaps. 05/03/05 @ 06:37 Comment from: Quantum Mirror [Visitor] Dear Peter Tanguay No that was a “Quote” from R. Srinivasan that there was confusion in TI! On page 19 of the preprint: “If PC is correct, then in any experiment, we must find h=0 since the observed value for R must be that of the decoherent case R’ due to the fact that we find no reduction in the resolution of the images as shown in Fig. 7(b), so that K=1. The presence of a perfect IP, would result in a R=0, and therefore would lead to an ideal result of h=1 . Bearing in mind the margins of error in our measurements, in this experiment we find that 0.97 is less than or equal to h is less than or equal to 1.1 again confirming a clear violation of PC.” “It is expected that this result can be improved upon by reducing the thickness e of the wires in the WG, yet maintaining the condition for opacity and increasing the resolution and sensitivity of the CCDs. “ I really don’t know why this last part was included. My guess he trying to error on the side of clarity and explain why the number is not a perfect 0 or 1. In my opinion the flux measurment of © only needs to be a fraction of the number established in (b) on page 33 to establish interference and sharp measurement. It has caused confusion before on this blog and I wish it had been left out! 05/03/05 @ 12:21 Comment from: Ruth Kastner [Visitor] Regarding one of R.S.’s earlier posts, he misstates what I’m saying in my quant-ph paper (arxiv.org). I do not advocate that the wave aspect is any more “real” than the particle aspect of the photon. I just point out that, since the system ( most accurately considered as an excitation of the em field) has been prepared in a superposition of slits, it may not legitimate to retrodict a determinate trajectory through a particular slit based on a post-selection at the final screen. This follows from the ambiguity of such inferences in pre- and post-selection situations (see some of my eprints on quant-ph concerning the ABL rule). I’d also like to point out that using a “conservation of linear momentum” argument to bolster a which-way information claim presupposes the very particle-like nature which is in dispute. 05/04/05 @ 19:09 Comment from: Quantum Mirror [Visitor] Dear Ruth Kastner Welcome to this blog. I had some questions about your paper. In your paper outlining the reasons against this paper and for complementarity you seem to suggest the basic nature of light quanta as laid out by Einstein is wrong: Einstein described light as “consisting of a finite number of energy quanta which are localized at points in space, which move without dividing, and which can only be produced and absorbed as complete units.” This view has remained unchanged since its inception. You seem to suggest in your paper that photons split in two through the slits and can no longer have an individual identity after they recombine. How do you justify this position? The wave-particle duality is the main point of demarcation between quantum and classical physics, and is the quintessential mystery of quantum mechanics. Do you believe that all the mysteries are solved? Do you think superposition is carved in the bedrock of quantum theory? I agree with Wesley that superposition principle is merely a mathematical convenience devoid of any direct physical or causal significance. 49. J. P. Wesley, Found. Phys. 14, 155 (1984). For a good review of the questions remaining in quantum theory: http://arxiv.org/ftp/physics/papers/0302/0302062.pdf This is also available in: Modern Physics Letters B 9 (1995) pp. 763 - 789 If you have access. Thank you for joining our discussions. I am sure prof. afshar will address your conservation of linear momentum concerns when he has time. 05/05/05 @ 08:17 Comment from: Rupert [Visitor] Dear Prof. Afshar, At the risk of seeming foolish, I was wondering whether you could explain to me exactly how a trajectory (ie which pinhole it passed through) can be ascribed to a photon based on which detector it reaches and the conservation of momentum? Surely if we define our photons as having momentum in the x-direction only before they pass through the pinhole(s) then we will find that after passing through the pinhole(s) each photon will be in a superposition of states with different possible y- and z- momentums. The momentum of the photon remains indeterminate up until the point at which it interacts with a detector. According to the Copenhagen Interpretation, as I understand it, this means that only upon interaction with the detector does it become possible to ascribe any momentum value to the photon; this does not mean that the photon possessed this momentum value all the time without us knowing it. As such, it seems bold to assert that the photon follows a determinate trajectory which corresponds to this momentum and to claim, on this basis, that the photon is displaying both particle and wave properties as it passes through the wire grid. In order to assert that the photon has a well-defined momentum which can be conserved do we not need to adopt a realist position - presumably one which appeals to hidden variables? Does the reasoning, therefore, perhaps anticipate the conclusion? Best wishes, Rupert 05/06/05 @ 14:50 Comment from: R. Srinivasan [Visitor] Dear Dr. Kastner, When you assert “since the system (most accurately considered as an excitation of the em field) has been prepared in a superposition of slits, it may not legitimate to retrodict a determinate trajectory through a particular slit based on a post-selection at the final screen.” it seems to me that you are still ascribing some sort of reality to the wave nature of the photon in order to ban the retrodiction of the path information. When you consider the superposition state as an “excitation of the em field", you have assumed the wave nature of the photon. If you claim that you are not making any commitment to the “reality” of the assumed wave nature, are you then asserting that the photon can, *by fiat*, have only one state at a given time and once it is deemed to be in a superposition state, it cannot *by definition* also have a definite trajectory? It seems that in the latter case, you are approaching the NAFL truth definition which asserts that mathematical truth for formal propositions consists of axiomatic declarations. The temporal nature of NAFL truth ensures that one can retrodict the path information, as described in my paper. The superposition state in NAFL only means that *no assertions* have been made regarding the (classical) trajectory of the photon; this does not prevent us from making a retroactive assertion of the trajectory when the information does become available. I am still not clear on what exactly is your philosophical position regarding truth for the status of the photon. Regards, RS 05/09/05 @ 00:03 Comment from: afshar [Member] Dear All, I am currently buried under another important deadlined task, but just FYI: Danko Gerogiev has withdrawn his “paper” from the PhilSci archive. I had made a recommendation to the editors of the archive to remove his paper, but if he’s done it voluntarily, I applaud that. Regards. 05/10/05 @ 04:28 Comment from: Quantum Mirror [Visitor] Dear Rupert “At the risk of seeming foolish, I was wondering whether you could explain to me exactly how a trajectory (ie which pinhole it passed through) can be ascribed to a photon based on which detector it reaches and the conservation of momentum?” It is a lot more complicated than that. Please read through the paper carefully and then similar questions on this blog. This will clarify your questions into a more reasonable form that would help to advance the science of QM and understand nature. Dear All I have been very busy of late also and will try to spend more time on my questions and answers in the future. After reading back my questions to Ruth Kastner, I sounded a little like Danco Gerogiev myself and must admit I did not go back and read her paper before asking them. I will try to do better in the future and make sure I have a clear picture of the physics involved before I open my keyboard (mouth). Physics is very complicated and it is wise to reread relevant materials and get a clear picture in your mind before you ask questions or make statements. I think we can all learn from Danco Gerogiev by never quickly skimming over material, making off the cuff statements and unreasonable assumptions without spending the time to familiarize ourselves with the related physics and references. 05/10/05 @ 06:07 Comment from: Fred Kiani [Visitor] To all scientists, I’m not a physicist; I’m more of a computer engineer scientist interested in revolutionary ideas in science. As a scientist I’m very interested to know the implication and affect of having COMPLEMENTARITY out (as it seems the case even for a non physicist like me, Prof. Afshar’s experiment has won all debates so far). My question is has anybody investigated what affect will this have on QM in a bigger picture or for that matter on all science in a bigger context? Since so many arguments in textbooks are base on the COMPLEMENTARITY theory. I went through all 567 comments and most of the papers suggested in this Blog, doing so helped me to realize very interesting fact that if we were wrong about COMPLEMENTARITY we could be wrong about so many other things. Quantum Mirror seems to be very active in this Blog (I’m personally thankful to him and Prof. Afshar), so I would appreciate at least some comments on the subject from him. Best regards, Fred Kiani 05/11/05 @ 05:57 Comment from: quantum enforcer [Visitor] Dear Fred Tounge in cheek offering: In New Scientist magazine Prof Afshar promotes the idea of the particle version of light (photon) may not in fact exist in a sense as it would appear that the photoelectric effect can be also be explained by the wave version of light to. So this makes light wavelike only and we only imagined particles really. That would be a far reaching implication of Prof Afshars work. However this might be ok for the quintessence of ineffability, ie light but as QM applies equally to matter particles it would seem odd then light (a force carrying particle) is a wave but mass particles are both, unless of course electrons are made up too in terms of particles. This would make protons and neutrons and hence quarks waves as well ? 05/13/05 @ 04:00 Comment from: quantum enforcer [Visitor] second paragraph should read: However this might be ok for the quintessence of ineffability, ie; light but as QM applies equally to matter particles it would seem odd then light (a force carrying particle) is a wave but mass particles are both, unless of course electrons are made up too in terms of waves only. 05/13/05 @ 04:03 Comment from: Quantum Mirror [Visitor] Dear Fred Kiani “I’m very interested to know the implication and affect of having COMPLEMENTARITY out ” I spent some time thinking about this. Since I don’t give complementarity any casual significance I don’t think anything will change except the way we think about the results of experiments. We will need to search for the real physical reasons that affect the outcome of these experiments such as decoherence or uncertainty. I think the closer we get to the truth the more the real casual aspects of QM will be apparent and the voodoo and spooky actions will be left behind. Most people that picture the quantum world see little particles and solid objects in their mind but what would be the make up of a solid object? Little tiny atoms? There is no such thing and the results of experiments may be trying to tell us that there is neither wave or particle but instead a single property we can not fathom in our mind. A warping or stretching of space time which is hard to imagine. 05/13/05 @ 15:46 Comment from: Alireza Naficy [Visitor] Please tell me: Are you still working on your opinion or no. If yes, have you reached to any new thing? Regards 05/15/05 @ 02:51 Comment from: Paul Valletta [Visitor] There are a number of recent papers that may be of interest Time Of Arrival concepts, which could help in understanding? :http://arxiv.org/abs/physics/0505134 And this for further conceptual notions about ‘time of clicks’ http://arxiv.org/abs/physics/0505134 [If a Photon moves by(across the line of sight a detector), there is some distance between each, the intervening space borders both observer and the observed. The question of what travels from one to the other? if a Particle travels across a line of sight, form a hidden location(unobserved) to one where it becomes detected, the moment it is regestered a, ” click on a photon detector", then it is at two locations, in one instant. Taking the Einstein local value for a Photon to be hv, interpretation by Bohr gives the Photon a Wave Quantity regestered at the detector, thus the particle-wave duality. In Ashfar’s experiment does not have ‘two’ detectors, a wave-detector AND a particle detector. The consequence of which becomes apparent if one does a variant of Ashfar’s experiment. If one does the experiment with TWO FOCUSING lenses instead of one(the second focusing mirror replacing the mirrors), with vertical wires placed on the opposite side of the second focusing lens, then the mirrors are place as for the original Afshar experiment. Iam asking if you have considered an extension to your experiment?.. If one has TWO focusing lenses, the second one with the vertical wires on the other side of the second focusing lens, would not this “reverse” your initial focusing lens, therby strengthening your experiment conclusions? ] in light of recent postings, I post my original question from your first blog. Can your experiment be structured with TWO-Lensses as above, and would another experiment with two lenses form a Strengthening of your original experiment?, obvious if it is found to be “reversable", thanks pv. 05/20/05 @ 18:45 Comment from: Luis Muzquiz [Visitor] Hi Fellas! just wanted to tell u this….about danko and afshar discussion abouth the existence of the photon and einstein´s nobel prize cause of the photoelectric effect…. In http://nobelprize.org/physics/articles/ekspong/ ( The Dual Nature of Light as Reflected in the Nobel Archive) says the nobel comitte didnt exactly gave the prize to einstein because of the photon existence…….so in a way, if the photon doesnt exists they dont have to take the prize away from him… it says… “…Now, does not the prize to Einstein imply that the Academy recognised the particle nature of light? The Nobel Committee says that Einstein had found that the energy exchange between matter and ether occurs by atoms emitting or absorbing a quantum of energy, . As a consequence of the new concept of light quanta (in modern terminology photons) Einstein proposed the law that an electron emitted from a substance by monochromatic light with the frequency has to have a maximum energy of , where is the energy needed to remove the electron from the substance. Robert Andrews Millikan carried out a series of measurements over a period of 10 years, finally confirming the validity of this law in 1916 with great accuracy. Millikan had, however, found the idea of light quanta to be unfamiliar and strange. The Nobel Committee avoids committing itself to the particle concept. Light-quanta or with modern terminology, photons, were explicitly mentioned in the reports on which the prize decision rested only in connection with emission and absorption processes. The Committee says that the most important application of Einstein’s photoelectric law and also its most convincing confirmation has come from the use Bohr made of it in his theory of atoms, which explains a vast amount of spectroscopic data…” Luis Muzquiz Z 05/22/05 @ 20:13 Comment from: Luis Muzquiz [Visitor] Just thought of a question …..so if photons doesnt exist, what is this thing they are measuring when trying to establish a limit on photon mass? Luis Muzquiz 05/22/05 @ 20:45 Comment from: Luis Muzquiz [Visitor] i just thought of something else…. Taking into account that the wave particle-duality and the nature of light is “the quintaessence” of quantum mechanics. and that now you are willing to seriously consider that light is only a wave…I think we can safely say, (just like feynman once said about quantum mechanics) that nobody understands the true nature of light. You may claim that you know what light is, and believe it. But, history tell us, that there will be a lot of scientists that will claim based on experimenation that light is the opossite thing you claim it is. (that is photon and a wave at the same time) We have reached a point where sometimes physics, even though we have experimentation, feels like a discution about religion or philosophy The only thing im sure now is theres no doubt that the nature of Light is a very profound mystery. Greetings Luis Muzquiz 05/22/05 @ 21:02 Comment from: afshar [Member] Afshar’s response to Kastner’s critique (form Wikipedia) Bohr’s Principle of Complementarity (PC) is concerned with mutually-exclusive measurements. In a welcher weg experiment PC allows either the measurement of a perfectly visible interference pattern XOR which-way information. In Afshar experiment, the visibility of the interference pattern is measured indirectly, so that almost all the “photons” make it to the image detectors. Therefore, both complementary measurements are made in the same experimental setup. In Kastner’s example of the superposed up and down spins, the only measurement that is made is the one after the Stern-Gerlach magnet, where two separate ensembles are observed. There is no complementary measurement of the superposition state to discuss; i.e. the |Up_x>+|Down_x> state has no measurable observable to demonstrate its presence, whereas the superposition of the wavefunctions emerging from the two pinholes in Afshar experiment (|Psi_1>+|Psi_2>) present well-defined observables such as the spatial locations of the bright and dark fringes etc. In short, Kastner’s spin superposition argument has nothing to do with PC, simply because there is only the |Up_x> and |Down_x> observables and no complementary observable pair demonstrating the superposition state, and therefore cannot be used to defend PC. Also, since Kastner’s paper critiques Afshar’s which-way argument, it is important to note that she does not disagree with the fact that the wavefunctions ending up in each image have one-to-one relationships with the pinholes (this according to personal communications). If so, in light of the above rebuttal regarding her spin measurement argument, Kastner should have no problems with Afshar’s final conclusion that PC fails in his experiment, which is based entirely on the commonly used concepts in the literature concerning the visibility of the interference pattern and the which-way information. Although in QM the formalism for all uperposition states is the same (summation of all amplitudes), it is crucial to realize that NOT all superpositions are logically equivalent (at least as far as physical observables and the PC are concerned!) 05/22/05 @ 23:32 Comment from: Peter Tanguay [Visitor] Afshar, What is the publishing status of your manuscript ? Any new timeline? Peter Tanguay 06/02/05 @ 02:25 Comment from: Peter Tanguay [Visitor] Dear Professor Afshar, What is the upper limit on the size of the wires, and still non destrictively record an interference pattern? I have some ideas, but would like to hear from you as to exactly what the limiting criteria would be. In the preprint, It is my understanding that for the coherent case: ” R= (-0.1 +/- 0.2%) indicating that the WG has not absorbed or reflected a measureable amount of light within the margin of error, thus establishing the presence of dark fringes…..V=1.” Although I see this as true, could you elaborate as to just how large the wires could be? Of course, one would try to keep the wires as small as possible, but it would give great insight into the ability to successfully measure a wave IP through non destructive means. Regards, Peter Tanguay 06/07/05 @ 09:28 Comment from: afshar [Member] Hello everybody, I am traveling right now, but will have more detailed updates by the end of June. I have proposed two new experiments and one of them will provide results by August, hopefully in time for the SPIE meeting in San Diego. In Sweden I reported the successful completion of an alternaitve version of my experiment, in which there is no imaging lens involved, and which-way information is obtained directly from the conservation of linear momentum considerations. This would refute claims by some critics as to the validity of which-way information in my previous experiment. This paper will be published by American Institute of Physics, and will be available online in July. Regards. 06/10/05 @ 14:18 Comment from: Ruth Kastner [Visitor] Prof. Afshar’s Wikipedia entry, quoted in his comment above of 5/22/05, contains an incorrect statement about my spin thought-experiment. My spin experiment indeed allows for an intervening, nondestructive measurement of spin along x, between the initial state preparation and the final detection, analogous to his wire grid (one can think of a Stern-Gerlach oriented along the x direction, with a detector only for “down along x"–no particles should be detected there, just as no photons should be detected by the wires). This is discussed on page 4 of my paper as posted on the PhilSci archive. I am disappointed to see a misstatement of what is in my paper posted on Wikipedia, and hope that interested people will read my paper and judge for themselves what my argument regarding the Afshar experiment is actually about. I would also note that the Wikipedia hosts have posted a warning to the effect that the Wikipedia entry on this topic does not appear to be neutral as requested in their policy. They are probably correct about this. My entry on that page simply aims to point out that there is another interpretation of the results of the Afshar experiment, which people may read about in my paper. However, I am going to contact the Wikipedia hosts and ask if they would like me to remove my entry. If so, I would encourage anyone else who feels that their entry may not be neutral on this topic to do so as well. 06/17/05 @ 13:49 Comment from: Peter Tanguay [Visitor] Dear Dr. Kastner, It is good to hear a truly scientific debate on the blog. After Reading both papers and the blog, I do not see what two complementary variables are measured in your cited spin experiment. I see a possible nondestructive measurement of spin, but not two complimentary variables. Would you respond? I am an advocate of the Transactional Interpretation, and I am puzzled why one would want to refute the Afshar Experiment in order to promote TI. I see the Afshar experiment as the strongest vehicle for TI promotion. Do you see that because he did not include TI as an explanation in his paper that it is remiss? According to comments from Afshar in the blog and from your paper, we would all seem to be in agreement that a wave-like interpretation such as TI is a best fit model to the afshar experiment. Your comments please. Regards Peter Tanguay 06/22/05 @ 02:41 Comment from: Quantum Mirror [Visitor] Dear Prof. Afshar I was wondering if you had more information on the alternative version of the experiment in which there is no imaging lens involved. Do you have a preprint ready? What are the proposed experiments you are trying to complete that will provide results by August? Any information I would enjoy reading and maybe in some small way contribute. You can email if you do not want a public disclosure. Good to hear that your paper will be published and finally some recognition for all your hard work. All the best! 06/25/05 @ 14:59 Comment from: Quantum Mirror [Visitor] Dear Peter Tanguay “It is good to hear a truly scientific debate on the blog.” Where is the debate? We have Kastner holding hit and run remarks and never responding to questions. She will hold on to the last dying breath of Copenhagen with any spin she can imagine to obscure and obfuscate. I can’t find the debate you are talking about. 06/26/05 @ 03:26 Comment from: Peter Tanguay [Visitor] Dear Quantum Mirror, She has not answered Prof Afshars question of complimentary variables, but perhaps she is formulating a response. Her entry on 05-04-05 helped clarify her position and on 06-17-05 graciously offered to remove an entry in Wikipedia. I may not wholly agree with her position , but one should refrain from personal attacks such as “She will hold on to the last dying breath of Copenhagen with any spin she can imagine to obscure and obfuscate.” In order for a scientific debate, one needs to create a climate where errors are not attacked, but acknowledged as a contribution to science. (e.g. finding the 999 ways not to make a light bulb.) Peter Tanguay 06/27/05 @ 02:47 Comment from: Quantum Mirror [Visitor] Peter Tanguay I did not intend in any way, form or stretch of the imagination to attack her personally. Where did I mention anything personal about her? I made a comment about her physics! This is quite different than your comment “It is good to hear a truly scientific debate on the blog” which is entirely a personal attack on the regular posters of this blog. You carry on with your scientific debate fantasy, I will not interrupt this great debate any further!! 06/27/05 @ 21:43 Comment from: Peter Tanguay [Visitor] quantum mirror, let us agree to disagree on this matter. Peter Tanguay 06/28/05 @ 03:34 Comment from: Sun [Visitor] Has anyone heard from Prof. Afshar since his return a few days ago? 06/29/05 @ 11:37 Comment from: Harry Nielsen [Visitor] Dear Professor Ashfar, My first comment is to applaud you for the ground breaking nature of your work, and the care and thoughtfulness with which you are conducting this discussion. I also feel this blog is a marvellous example of how the internet can be used for a form of open peer review - as opposed to the usual secret process organised by the “names” in a subject. I have a very simple question, which is to ask if you have any more information on the single photon form of your experiment? If (if!) you are able to show a few images from those results I think they would rank as the most astonishing experimental results from a physics experiment for many decades. WIth best wishes, Harry Nielsen p.s. I am a research scientist of 25 years standing, working currently in acoustics (lot’s of lovely wave theory!) and with a training in theoretical physics at graduate and postgraduate level. 07/05/05 @ 03:03 Comment from: Mike [Visitor] In the double slit experiment, you have both wave and particle behaviour. There is always interference between the two slits (wave), but each individual photon is observed as a particle. So where is there anything new? 07/08/05 @ 01:34 Comment from: quantum enforcer [Visitor] Because you cannot allegedly show both types of behaviour at the same time. Prof Afshar has done precisely that. 07/11/05 @ 01:05 Comment from: Harry Nielsen [Visitor] There is an article on the Copenhagen Interpretation which references Professor Afshar’s work at http://www.marxist.com/scienceandtech/quantum-mechanics-copenhagen150605.htm With reference to the comment from Mike ("In the double slit experiment, you have both wave and particle behaviour…….. So where is there anything new? “) the article comments: “Born’s probability interpretation allows the physicist to compute the relative probability of the particle arriving at a certain position. But the probability, or the wave-function, is only a statistical property of the system, and each individual arrival can be (almost) anywhere. We become aware of the wave behaviour of matter only when we have many particles. Similarly, in a gas we observe the laws that connect temperature, volume and pressure only when we have many molecules. Wave-like qualities emerge in a transition from quantity to quality; one particle or molecule is unpredictable, but many obey well-defined laws conforming to their statistical properties. Both waves and particles are observed – individual particles, which in large groups have the properties (interference patterns) of waves. In that sense, single particle experiments and images of the sort obtained from the Hitachi experiment [a double-slit experiment with single electrons] also directly contradict Bohr’s principle of complementarity.” 07/13/05 @ 08:08 Comment from: Quantum Mirror [Visitor] Dear Prof. Afshar and all A new and very important preprint has just been posted to: From the paper: The crux of our new effects is that the 4D Bell-like ITE state allows us to extract near–complete information by internal-state projections on propagation along two interfering paths without the constraints of standard complementarity. The resulting path and phase information is real and verifiable, and so is the accuracy increase (eq. 11). Such intra-particle entanglement may become a new resource of quantum information. The fact that ITE objects can display, nearly perfectly, both corpuscular and wavelike properties, suggests that waveparticle duality requires revision. 07/20/05 @ 12:58 Comment from: Quantum Mirror [Visitor] Dear Professor afshar “This paper will be published by American Institute of Physics, and will be available online in July.” I can’t find this paper in the AIP website. It is very confusing site and makes reference to their new free search but I don’t think I was searching the right documents. Do you have a link to the journal where it is available? 07/24/05 @ 16:13 Comment from: afshar [Member] Dear friends, Sorry for the long hiatus, too many balls to juggle, too little time! The high-flux experiment performed at Harvard is finally published in Proc. SPIE 5866, 229 (July 2005). The Rowan single-photon paper is under peer-review with PRL. The crossed-beams version of the experiment will appear in the AIP conference proceedings (will know volume and page in Sept.) The experiment involving entangled photons is still not complete, it may take another couple of months. If somebody has the time to cook up a series of Q&As from the Blogs (1&2) I would highly appreciate it, as we can avoid redundancies. Please e-mail the Q&A to me for a quick look, and then I will post it on my web-page along with an acknowledgement of the individual who helped. As for Kastner, I see no relevance in the Spin measurement argument to my experiment, as there is no unique complementary observable for the superposition state in her suggested example. Again in order to even discuss Complementarity, you need uniquely defined complementary observables, which are lacking in Kastner’s gedanken. To Mike: Contrary to common belief, NON-complementary wave and particle behaviors CAN coexist in the same experiment in complete agreement with Bohr’s Complementarity principle (as in the formation of an interference pattern by single photons.) Only complementary observables cannot coexist according to PC, which my experiment violates. See Ref.[20] in my preprint: G. Kar, A. Roy, S. Ghosh and D. Sarkar, Los Alamos National Laboratory e-print (http://arxiv.org/abs/quant-ph/9901026); S. Bandyopadhyay, Phys. Lett. A 276 (2000) 233. Have a great summer! Regards. 07/26/05 @ 07:55 Comment from: Danko Georgiev [Visitor] Dear All, I just noted that some of the persons that post morefrequently here do not try to keep any scientific and rational discussion, but instead are attracted by the “fuss” around the wrong interpretation of Afshar. I will point just several crucial facts: 1. Paper if published in Proceedings book is not counted as real publication! I hope that Afshar realizes that, so he can count his work AS IF it is not passed peer-reviewing at all. 2. I have removed my paper from PhilSci because I want to add some computer simulations in order to make it clearer. The work is in process of finalizing, and possibly will be submitted for peer-reviewing soon. 3. One if interested about the essense of my argument then he/she can check this preprint: http://www.geocities.com/dankomed/afshar.pdf There is no “which way” info even if there is no grid before the lens!!! None of the following researchers: Motl, Unruh, Kastner, Cramer, Drezet, etc. has correctly diagnozed this major loophole. 4. The fact that Afshar blocked one I.P. adress not not mean that I cannot post on his blog from any computer in the world that I want. Actually I don’t want to play such stupid games, and I hope that Afshar will be clever enough to be open for conversation and will try really human-like dialogue. [I really will not reply to any of the following replies to me on this blog. Any discussion is welcommed at: dankomed@yahoo.com and I welcome Afshar’s comments as well by e-mail] ——- Just to clarify my argument: 1. Suppose that you put different polarization filters at the two pinholes, say R and L. Then the photon’s wavefunctions for each slit are DISTINGUISHABLE what you will have is P[ww] = |psi_1|^2 + |psi_2|^2 distribution and putting a grid before the lens will lead to photon diffraction!!! In this case there is “which way” info/experiment 2. Suppose you now have Afshar’s setup without polarization filters. Then the photon’s wavefunctions passing through each slits are INDISTINGUISHABLE and one can expect to observe P[nww] = |psi_1 + psi_2|^2 distribution. Then putting a grid before the lens will not lead to photon diffraction!!! This is “NO which way” info/experiment. Now think about the images at the image planes in case 1 and 2. In both cases the pinholes are perfectly focused (!) so one can expect that the image at the image plane can be almost identical for both functions P[ww] and P[nww]. However both functions are 3D and you cannot always distinguish between them when you observe only a single 2D plane, because this plane can be a “cross-plane” for both functions. Mathematically one can have two 1D functions f(x) anf g(x) and suppose that each of these functions can take value y=2 when x=2. This is a “cross-point” of these hypotetive functions so from knowing that it is x=2 and y=2, you cannot say whether this is f(x) or it is g(x) Now how you can distinguish between these two functions? Well, it is elementary - you should look at a “non-cross-point” and from your observation you will rule out one of the functions and you will prove the other. Now back to Afshar’s setup: the image at the image plane is the same when you have differebtly polarized photons, and when you have coherent ones. Therefore you cannot say BY DEFAULT whether it is “which way” experiment or NOT by observing this “cross-plane” for the two 3D functions. You can however look in non-destructive way [with a grid put in the wavefunctions minima(!) exactly as Afshar did]. You then get “there is interference = non-which-way” or you get “there is no interference/there is photon diffraction = “which way". So do you see what i am saying?!!! The premise of Afshar that his experiment is which way when there is no grid is WRONG, and it is the cause for contradiction. Adding or removing the grid does not change anything about the essense of the experiment. The grid is a tool for detecting a difference between the two probability distributions/functions P[ww] and P[nww] and it is of use if you detect at a cross-plane of the two 3D functions [like the image plane]. If one can really profit from my comments, I will be glad to reply by e-mail. Best, Danko Georgiev 07/30/05 @ 07:50 Comment from: afshar [Member] Dear Danko, “There is no “which way” info even if there is no grid before the lens!!! None of the following researchers: Motl, Unruh, Kastner, Cramer, Drezet, etc. has correctly diagnozed this major loophole.” I allow your posts now that other physicists (who may disagree with my interpretation of the experimental results, yet are decent enough to defend the obvious truth) have pointed out your error vis-a-vis the presence of reliable which-way information (WWI) in the images produced by a lens. As I said many times before, the images carry the WWI as pointed out first by Bohr, Heisneberg and later by Wheeler and many others. That said, I will make your task a bit easier by giving you an experiment in which no imaging lens is present; only two mutually-coherent beams that cross over in a small region of space, and then evolve with no overlap further downstream. Indeed if you had read my earlier posts back in Nov. 30, 2004, you would have know about this experiment (which is now carried out and to be published in AIP proceedings) you would not have gone through the pains of copy and pasting an article against the established fact of presence of WWI in well-resolved images. Nonetheless, I am sure you have learned a thing or two along the way, which is always a good thing. Now back to the new experiment. In this FIGURE you see the two beams crossing each other at Sigma_1, and then completely separating at Sigma_2 (there are no wires present at Sigma_1). Please answer the following questions as briefly as possible: 1) If you see a photon at D_1 can you say it came from pinhole 2, and how? 2) Do you consider the probability distribution at Sigma_2 to be an interference pattern (IP)? If so what is the visibility of this IP? 3) Do expect an IP at Sigma_1? 4) Does presence of a wire grid at the dark fringes of the IP (as in the original experiment) at Sigma_1 change anything in the experiment? Let me assure you that the obtained experimental data is in full agreement with my initial experiment. Regards. 07/31/05 @ 06:24 Comment from: Drezet [Visitor] dear Dr. Afshar, I dont know what will be the answer of DG will be . You are right that he is 100% wrong on his interpretation of QM, electromagentism and even optics. So if you try to convince him of anything you will enter in a perpetual motion… for me the uniqual non trivial question in your list 1to 4 is the first one: can we attribute a causal realtion to a photon detected in sigma2 say in 1′ and conculde that this photon came from the pinhole 1. This question which ask about the relevance of the concept of trqjectory can not be answered in generla in the context of QM. QM doesnt describe univocally what is happening to a system between two observations and this was the basis fro the copenhagen interpretation. the ontological level not considered by this Bohr point of view can only be treated in specifical models like Bohm or manyworlds models. However theses models can not be tested experimentally ( or if they can they are not completely equivalent to QM ). to finish I would like to say to DG that an article of conference is certainly an important point even if a PRL is much better. Even if I desagree with S. Afshar on his interpretation your argumentation is meaning less since very important thing can be found in proceedings with best regards to every body Dr aurelien Drezet 07/31/05 @ 08:23 Comment from: Danko Georgiev [Visitor] Dear prof. Afshar, Thank you very much for your reply. I am interested in application of QM to study molecular dynamics in brain, that is why I am currently studying the basics of QM. I study things step-by-step and actually you still haven’t anwered my main question about the distingushability of mathematical functions when observing only their “cross point” [see my previous post]. Below I reply to your question: 1. The fact that at sigma_1 THERE IS IP says that the photon registered at D1 or D2 does not carry WWI. You can think that the photon is holographically at both detectors at the same time \psi = (|D1> + |D2>) [normalization omitted], so that the final detection just “projects” the superposed photon in basis |D1>, |D2>. The probability for each detection is 1/2, but there is NO WWI, because the photon is in superposition, not is mixed state. Note that the density matrix is a pure state matrix \rho = 1/2|D1>, |D2> gives you exactly the same results of 1/2 as in the previous case 1. HOWEVER the lack of IP at sigma_1 is indicator that THERE IS WWI! I think I have clarified my position, and I am curious to understand why so great physicists think there is WWI at the image plane, overlooking the simple fact that the photon’s wavefunctions for each slit are indistingushable and the photon in this NO WWI case can be coherently at both detectors. If i can afford a metaphor in WWI each photon at the image plane carries only “pixel” of the image plane and it is not aware of the rest of the picture that will be produced after registering enough photons. in NO WWI each photon at the image plane carries “holographic info” about the whole picture and “knows” the whole image at the image plane. Only the “projection in basis x” forces him to “collapse” irreversibly from the superposed holographic state into a “local pixel state". Kind regards, Danko Georgiev 08/02/05 @ 13:01 Comment from: Danko Georgiev [Visitor] Dear prof. Afshar, Thank you very much for your reply. I am interested in application of QM to study molecular dynamics in brain, that is why I am currently studying the basics of QM. I study things step-by-step and actually you still haven’t anwered my main question about the distingushability of mathematical functions when observing only their “cross point” [see my previous post]. Below I reply to your question: 1. The fact that at sigma_1 THERE IS IP says that the photon registered at D1 or D2 does not carry WWI. You can think that the photon is holographically at both detectors at the same time \psi = (|D1) + |D2)) [normalization omitted], so that the final detection just “projects” the superposed photon in basis |D1), |D2). The probability for each detection is 1/2, but there is NO WWI, because the photon is in superposition, not is mixed state. Note that the density matrix is a pure state matrix \rho = 1/2|D1)(D1| + 1/2|D1)(D2| + 1/2|D2)(D1| + 1/2|D2)(D2|. 2. Suppose now that you have put different polarization filters at each pinhole at the lens surface [I comment on the FIGURE 1 of yours in your previous post]. Then THERE IS NO IP at sigma_1 and still the photon is focused either on D1 or focused on D2. The photon’s state is now “mixture” and cannot be written with pure state wavefunction unless you actually know through which pinhole it will pass. The density matrix is \rho = 1/2|D1)(D1| + 1/2|D2)(D2| and there is WWI. Measuring of this mixed state in basis |D1), |D2) gives you exactly the same results of 1/2 as in the previous case 1. HOWEVER the lack of IP at sigma_1 is indicator that THERE IS WWI! I think I have clarified my position, and I am curious to understand why so great physicists think there is WWI at the image plane, overlooking the simple fact that the photon’s wavefunctions for each slit are indistingushable and the photon in this NO WWI case can be coherently at both detectors. If i can afford a metaphor: in WWI each photon at the image plane carries only “pixel” of the image plane and it is not aware of the rest of the picture that will be produced after registering enough photons. in NO WWI each photon at the image plane carries “holographic info” about the whole picture and “knows” the whole image at the image plane. Only the “projection in basis x” forces him to “collapse” irreversibly from the superposed holographic state into a “local pixel state". Kind regards, Danko Georgiev 08/02/05 @ 13:06 Comment from: Danko Georgiev [Visitor] Please read just the last post. The usage of the bra-ket notation somehow affects the posting, and i have replaced the “>” symbol for “)". Danko 08/02/05 @ 13:08 Comment from: Quantum Mirror [Visitor] Danko Georgiev Have you seen a doctor in relation to your bipolar manic/depressive personality? I would say by your perception of your competency in quantum mechanics it is showing a rather long phase, which makes it hard to diagnose. I would seek counseling immediately before it does damage to your reputation. 08/04/05 @ 08:45 Comment from: Peter Tanguay [Visitor] Danko, I have over 7 years of holographic experience including my own company. I am also published in quantum mechanics,yet I have no idea what you are talking about. if you have made yourself clear, I do not see how. Part of being a scientist is to be able to effectively communicate your ideas to others. Working with others, not against them, is the only way to get someone to listen. I am afraid that I only see you sounding rambled and confused. Peter Tanguay 08/05/05 @ 03:55 Comment from: Keith [Visitor] Hi, I’m struggling to see where the problem is with the interpretation of Afshar’s experiment. Perhaps someone can help? The wires in front of the lens constitute a measurement of the interference pattern, and hence a measurement of the fact that the photon has gone through both pinholes. The later subsequent measurement, which attempts to obtain which way information, seems to me entirely consistent with the photon having gone through both pinholes. If it had only gone through one, you would expect a reduction in intensity, whereas if it went through both you would expect no reduction. No reduction is observed and the photon arrives 50% of the time at each detector, exactly consistent with it going through both pinholes! I would have expected a fuss if this experiment hadn’t done what you expect, why is there one when it does? Keith 08/10/05 @ 09:32 Comment from: afshar [Member] Dear Keith, Here’s what all the “fuss” is about: Complementarity predicts that if you have established an interference pattern, then the photons arriving at the image plane should contain no which-way information. ALTHOUGH A SINGLE PHOTON CAN ONLY ARRIVE AT A PARTICULAR IMAGE (P=50%) OF THE TIME, ALMOST ALL OF THE TIME (K=100%)THE PHOTON LANDS IN THE RIGHT IMAGE. i.e. each image is still intact and one can tell which of the two pinholes the photon originated from with an almost 100% accuracy. Complementarity predicts that the images must be washed-out so that you can no longer tell where a particular photon originated (K=0%), but we still observe two crisp images contrary to its predictions. It is important to distinguish between P and K. If you need more clarification please let me know. Regards. 08/10/05 @ 13:45 Comment from: Keith [Visitor] Hi, thanks for the reply. I think I do need a little more clarification. I know what you mean by “washed out” in terms of the standard two slit experiment (when you cover up one slit, and attempt to determine the origin of photons, the interference pattern dissapears and you get a relatively smooth distribution of light on the screen), but it seems to me that the equivalent of “washed out” in your experiment is that you should observe two crisp images rather than just one. The photon can only reach one of these two places. Before the measurement you have no idea which it is going to be. After repeating many times you discover that it gets to each 50% of the time, and there is no reduction in intensity. This implies the wavefunction at the detectors is a superposition of the two images, consistent with the photon having gone through both pinholes and an interference pattern being formed at the wires. Keith 08/10/05 @ 22:53 Comment from: afshar [Member] Dear Keith, Imagine that N_Total=200 photons are registered at the image plane, N_U=100 in the upper image and N_L=100 in the lower image. Now, out of the N_U=100 that end up in the upper image, all 100 come from the LOWER pinhole and similarly for the lower image, all 100 come from the UPPER pinhole. Complementarity demands that EITHER we should only have one blob in the image plane (so we cannot assign where each photon originated), OR if we have the two images, it must be such that 50% of EACH image should come from the “wrong” pinhole. This means that, say for N_U=100, we have 50 photons from the upper pinhole and 50 from the lower one to make up the 100 photons observed at that image. However, that is an IMPOSSIBILITY, because if that were the case, upon moving just one of the pinholes, half the intensity in both images must move to a new position on the image plane, which is not what happens. What we observe is that ALL the photons arriving at a particular image co-move with the corresponding pinhole. 100% OF THE PHOTONS IN EACH IMAGE COME FROM THE CORRESPONDING PINHOLE, THUS K=1. IN CONTRAST, COMPLEMENTARITY PREDICTS THAT 50% OF PHOTONS IN EACH IMAGE SHOULD COME FROM THE WRONG PINHOLE (K=0), WHICH IS NOT WHAT WE OBSERVE. YOU SAY: “This implies the wavefunction at the detectors is a superposition of the two images.” In order to see the EVIDENCE for superposition in the image plane, we MUST see a spatial interference pattern (without which we cannot confirm spatial superposition). This can ONLY happen if the two wavefunctions overlap spatially, which does not take place in the image plane. This is ESSENTIALLY why we have highly reliable which-way information at the image plane. I have explained this in as simple a manner as I can, and I hope you can see the point. Please reflect a while on the above argument, and only after you do that let me know if you still have further questions. Regards. 08/11/05 @ 00:25 Comment from: Keith [Visitor] Hello again, I see where you are coming from but I cannot concur. I disagree with your second sentence (as, I believe, does conventional quantum mechanics), and therefore with everything that follows. To the extent that you have measured the interference pattern (which itself is debatable) you have lost the which way information. The viewpoint I have outlined seems entirely consistent with QM and complementarity (and reality). Thank you very much for your responses, I have no more questions. Keith 08/11/05 @ 05:39 Comment from: afshar [Member] Dear Keith, You have made a couple of truly bold statements above which cannot go unanswered due to the seriousness of the implications of my experiment. So, now it is my turn to ask you a couple of questions, if I may! You say: “To the extent that you have measured the interference pattern (which itself is debatable)…” In your first comment on this Blog on 08/10/05 however, you seemed to agree that we have a reliable measurement of the interference: “The wires in front of the lens constitute a measurement of the interference pattern, and hence a measurement of the fact that the photon has gone through both pinholes.” Just so we understand each other: 1) Do you still believe that the wires establish the presence of interference or have you changed your mind? You also say: “I disagree with your second sentence (as, I believe, does conventional quantum mechanics), and therefore with everything that follows.” I take it that you disagree with this sentence of mine: “Now, out of the N_U=100 that end up in the upper image, all 100 come from the LOWER pinhole and similarly for the lower image, all 100 come from the UPPER pinhole.” It would be helpful to know the extent of your expertise in QM, beacause if you said the above as an amateur, then it is an entirely meaningless statement (i.e. “Not even wrong!"), but if you are a professional, then you are just simply wrong! Actually, “conventional quantum mechanics” agrees completely with my above assertion. It also shows that you have not read my previous posts that address exactly the same issue. In fact, I have announced a$1000 prize for anyone who can show EACH image has a 50-50 contribution from EACH pinhole. If you indeed believe my assertion is incorrect, please either post here, or e-mail me your QM calculation that shows “EACH image has a 50-50 contribution from EACH pinhole.” In more than a year, no one has been successful in doing so, including a couple of Nobel laureates; but who knows, you may have the answer, which would then certainly merit a Nobel prize on its own!

2) Just to make things easier (no need for Fourier analysis of the imaging lens) please use the arrangement shown in this FIGURE to show that EACH detector (D_1 or D_2) has a 50-50 contribution from EACH pinhole.

Best of luck!

08/11/05 @ 09:31
Comment from: Keith [Visitor]

Dear Shariar,

I guess that’s only fair! My background is in theoretical condensed matter (stongly correlated electrons), so I have spent a lot of time thinking quantum mechanically rather than classically.

As far as the wires establishing an interference pattern is concerned, it might be worth clarifying what I was thinking. Ideally, in your experiment, you would like to apply a projection operator before the lens to guarantee the presence of the interference pattern. Your wires clearly do this to some extent, although I’m sure you’ll agree it is not a perfect projection. I meant to say that the extent of this projection was debatable (perhaps it is actually calculable), but that I was willing to accept it as a perfect projection, because I didn’t think that this was where the problem lay.

So from a theoretical, thought experiment, viewpoint your setup (either one) consists of a wavefunction localised at two points (pinholes), a projection operator onto an interference pattern (wires), and a measurement at two localised points (detectors).

My point is simply that the projection is a projection onto a photon which came from both pinholes, and that the subsequent measurement at the detectors is entirely consistent with this.

Talk of which pinhole a photon came from is rendered meaningless by the projection.

Keith

08/12/05 @ 05:28
Comment from: Paul Valletta [Visitor]

Here is a paper that tackles your experiment :
http://arxiv.org/abs/gr-qc/0508045

I have not read it fully, so hopefully others can expand on its content?

08/12/05 @ 12:40
Comment from: afshar [Member]

Are you sure this is the right paper?!

08/12/05 @ 14:10
Comment from: Quantum Mirror [Visitor]

Dear All

Aurelien Drezet has a preprint on arxiv entilted:

Complementarity and Afshar’s experiment

http://arxiv.org/PS_cache/quant-ph/pdf/0508/0508091.pdf

I have not had time to read it yet but hope to on this weekend.

08/12/05 @ 16:50
Comment from: Quantum Mirror [Visitor]

Dear All

I have had time to read the paper now and I see we are dealing with the dogma of those that think quantum physics is a witches brew of principles and rules that have no ties to the real world. Take the following excerpt from the preprint:

He supposes
that the small value of R ∼ 0.1% is sufficient to deduce
the existence of fringes without measuring them. This
a logical inference in the context of classical optics
but this is forbidden in quantum mechanics since we
need different photons to observe both interference and
images patterns.

Different photons? The photon is a exchange of energy from one atom to another. Once it has reached its target atom the photon exists no more. Everyone knows (or at least I hope they do know) we can’t use the same photon twice. What has this to do with what is happening in the experiment? Everyone must agree with the fact that there is interference in the area of the wire grid or explain how the photons passed by this area without hitting the wires. AD wants physics to be like religion, a unexplainable dogma that requires a special “priest” interpreter to explain it to the unknowing. We are finding more simple explanations for quantum weirdness every day and moving away from the Voodoo and from Copenhagen. If you want to understand quantum physics, follow the simplest explanation without magic, priests, and interpretations and you will be closer to the truth.

08/13/05 @ 09:03
Comment from: Paul Valletta [Visitor]

Afshar Yes, I had posted another paper instead of the one by Aurelien Drezet!

Sorry for the inconvience.

08/14/05 @ 11:02
Comment from: Paul Valletta [Visitor]

Aurelien Drezet had communicated with Dr Afshar early in the first forum. His recent paper details some interesting aspects of experiment and interpretations, hopefully I will finish reading the paper soon, and re-read threads for some extra guidence of Dr Afshars stance.

08/14/05 @ 11:07
Comment from: Mike Dams [Visitor]

The main objection to the experiment seems to be about whether photons arriving at detector one definitely come from pinhole 1. Prof Afshar did a test by moving one of the pinholes while simultaneously adjusting the grid to maintain correct placement and observing that only the image corresponding to that pinhole moved.

Some critics might argue that moving the grid in unison with the pinhole artificially maintains some unknown factor such that only one of the images moves even though it consists of photons from both pinholes. In order to eliminate this I suggest that the procedure be adjusted as follows:

Make the movement of one pinhole very small, small enough to prevent the original grid placement from becoming misalligned but big enough that the resultant movement in the image can be detected electronically even if it is not visible to the naked eye. If you vibrate the pinhole in this way and are able to pick up a vibration in only one image then the argument can be put to rest. On the other hand if you find both images vibrate then you’ve got some explaining to do.

08/15/05 @ 03:45
Comment from: Keith [Visitor]

Moving the pinholes makes no difference. A photon getting past the wires still went through both pinholes. It doesn’t matter what the two images do.

08/15/05 @ 06:00
Comment from: Quantum Mirror [Visitor]

Dear Kieth

You said:
“Moving the pinholes makes no difference. A photon getting past the wires still went through both pinholes. It doesn’t matter what the two images do.”

You do not understand this experiment. If you do understand it, please provide us with a complete formal argument based on quantum and optical mechanics.

08/15/05 @ 08:18
Comment from: Keith [Visitor]

Quantum Mirror,

Really? Are you sure?

I’m sorry if you didn’t understand the argument I provided.

I’m really only saying that

1) measurement=projection.

2) Afshar’s wires are an attempt at projection onto an interference pattern and therefore also onto a state where the photon went through both pinholes.

3) If the wavefunction has been projected onto a state which went through both pinholes then the subsequently measured photon also went through both pinholes.

and that’s as complete as is needed.

Keith

08/15/05 @ 08:58
Comment from: Quantum Mirror [Visitor]

Dear Kieth

You said:
2) Afshar’s wires are an attempt at projection onto an interference pattern and therefore also onto a state where the photon went through both pinholes.

3) If the wavefunction has been projected onto a state which went through both pinholes then the subsequently measured photon also went through both pinholes.

It is your contention that a photon divides into two pieces, goes through both pinholes and recombines into a single photon. Where is the references to any experiment or theory that indicates a photon can be divided and recombined?

08/15/05 @ 09:31
Comment from: Keith [Visitor]

“It is your contention that a photon divides into two pieces, goes through both pinholes and recombines into a single photon.”

YES! Exactly! You’re getting the hang of this quantum mechanics malarkey.

Keith

08/15/05 @ 22:17
Comment from: Quantum Mirror [Visitor]

Kieth said:

“YES! Exactly! You’re getting the hang of this quantum mechanics malarkey.”

Where are the references, you have not gotten the hang of this science malarkey. You can’t just proclaim something as fact and it is fact. You will not find any reference since none exist. The photon can not be divided and reassembled like some kind of putty. this is the failure of your argument. Next argument please!

08/16/05 @ 05:09
Comment from: Keith [Visitor]

I’m astonished. I didn’t provide any examples because the examples are ubiquitous. For instance, how can you understand the original two-slit experiment if you don’t think in terms of the photon going through both slits?

Keith

08/16/05 @ 05:22
Comment from: Peter Tanguay [Visitor]

Keith,

In the logical development of QM, a photon was devised to explain the logical inconsistency of wave energy not being absorbed or emitted in a continuous manner and being observed as a localized event. This would keep experiment consistent with the definition of a wave. However, logical consistency with a definition is disregarded when it comes to a photon (It can go through two holes and interfere with itself) in order to keep QM and Copenhagen intact. There is no way to disprove a theory that does not follow logical consistency. The development of the LCA is outlined in Afshar’s paper referencing the Bohr-Einstein LCA debate.

We used to call it malarkey or sometimes BS when someone didn’t use logic to prove a theory. The retort by advocates of Copenhagen is to imply that one is just not smart enough or open minded enough to understand it. The Afshar experiment is not accepted by advocates of Copenhagen because no matter what, their logically inconsistent theory can’t be disproved by logic or even experiment. .

Keith: If Afshars’ experiment does not disprove complimentarity, what could disprove it?

Peter Tanguay

08/16/05 @ 05:33
Comment from: Peter Tanguay [Visitor]

Keith,

” how can you understand the original two-slit experiment if you don’t think in terms of the photon going through both slits? “

the transactional interpretation of QM.

Peter Tanguay

08/16/05 @ 05:35
Comment from: Quantum Mirror [Visitor]

Keith said:

“For instance, how can you understand the original two-slit experiment if you don’t think in terms of the photon going through both slits?”

You have found the central mystery of quantum physics. It has driven many men mad and destroyed whole careers trying to answer that question. It has no real logical answer. The photon can be thought of as a exchange of energy between two atoms. While it is in flight it is a wave and can travel through many slits and holes but when it reaches its destination it may only leave the energy with one atom. The most direct route becomes the reality and everything else along the route disappears. Complementary says there can not be both at the same time wave and which way information in the same experiment but there is clearly both in this one. It is only because the experiment probes the interference pattern in a non destructive manner allowing both to be realized! Afshar is not saying he has the answer to the central mystery in this experiment. He is saying that the principle of complementary has an example that does not work and so should be removed as a principle.

08/16/05 @ 08:53
Comment from: Keith [Visitor]

QM,

So, you are saying that you support Afshar’s conclusions because you are unhappy with the fundamentals of QM, and have never managed to get your head around the implications of the archetypal two-slit experiment.

For instance you say, “While it is in flight it is a wave and can travel through many slits and holes but when it reaches its destination it may only leave the energy with one atom. The most direct route becomes the reality and everything else along the route disappears.".

This is incorrect. The most direct route does not become the reality. The actual route taken is still utterly uncertain, you only know where the photon was detected.

You also claim this “central mystery” has “no real logical answer". I’m not sure what you mean by this. There exists a scientifc theory which explains the two-slit experiment and Afshar’s experiment and a hell of a lot of other stuff besides. This theory is logically consistent and its predictions are not questioned. Everyone (in the loose sense of people who understand the theory) agrees on what it predicts, and it agrees with reality extremely well. These experts only seem to disagree on how to interpret it.

Personally, I think it is not interpretable in a way that would satisfy many people and I prefer to take it at face value. I’m waiting for some reason to change my mind on this, but I see no evidence to do so yet.

Keith

p.s.

Peter: Afshar could prove to me that complementarity was wrong either by showing me a thought experiment where it clearly doesn’t apply, or by proving that in his experiment the photon definitely only went through the relevant pinhole.

08/17/05 @ 05:51
Comment from: PCMF [Visitor]

Prof. Afshar, this is related to your momentum conservation argument. Would you please comment on that? Thank you! PCMF.

http://en.wikipedia.org/wiki/Testing_Which-Way_Lens

08/17/05 @ 08:45
Comment from: afshar [Member]

Dear All,

There seems to be a lot of confusion as to what is meant when we say the photon “went through both pinholes". This is bad language in the sense that nobody (including Bohr et al.) ever meant that a single photon somehow splits itself and goes through both pinholes. What is meant (ala Dirac) is that a single photon can participate in an interference pattern so that an accumulation of large such single photon measurements looks like an interference pattern with bright and dark fringes. What “goes through both pinholes” is not the single photon but its “wavefunction” which is not a physical thing. It only RESEMBLES a wave because it is spread out like a wave and carries information about both pinholes, not because it actually is a wave. It is just that Bohr claimed that if one could tell with certainty which of the two slits it went through, we should ignore the part of the wavefunction that went through the other pinhole and therefore end up with no cross terms which produce interference fringes. And most importantly there is not a particular MECHANISM by which this magical selection between wave-like and particle-like outcomes take place. The observer decides the outcome by setting up an experiment to answer which of the two modes of behavior the photon chose. Bohr thought that the two types of experimental setups MUST be mutually-exclusive. But my experiment shows otherwise.

Dear Kieth

You say: “Afshar could prove to me that complementarity was wrong either by showing me a thought experiment where it clearly doesn’t apply, or by proving that in his experiment the photon definitely only went through the relevant pinhole.”

I can answer this in two different ways:
1) If you can prove (using QM) that the probability of a photon arriving at a particular image from the “wrong” pinhole is 50%, I would withdraw my claim.
2) If you do not like the above, then please let me know that in general what kind of evidence would satisfy you that a particular photon went through a particular pinhole, and then I’ll discuss the problem using that method.

Alternatively, you can wait for my more theoretical paper on measurement theory to appear in PRA (it is currently under review).

Regards.

08/17/05 @ 08:52
Comment from: Keith [Visitor]

Dear Prof. Afshar,

I have though of a simple way of testing whether or not the wavefunction at the detectors is in an equal superposition of wavefunctions from both pinholes.

You can remove the detectors and replace them with mirrors which reflect the light back towards the central axis of your experimental setup (further over to the right in your diagrams, away from the lens). You can then place a screen at the place where the two beams cross. An observation of the presence or absence of an interference pattern will settle the issue once and for all.

I know where my money is.

Keith

08/17/05 @ 08:57
Comment from: afshar [Member]

Kieth,

I don’t see how that would resolve the issue. The result would certainly be observation of an intereference pattern. Please elaborate on what that would entail in your view…

08/17/05 @ 09:11
Comment from: afshar [Member]

Dear PCMF,

Yes, theoretically a perfect coincidence would be observed. But be careful about using photon pairs, as you cannot observe a first order interference pattern ingeneral.

Regards

08/17/05 @ 09:13
Comment from: Keith [Visitor]

Dear Afshar,

Well, yes, clearly you would see an interference pattern. This demonstrates that in the original image plane there was a spatially separated superposition of wavefunctions, which is something you disputed earlier.

I don’t think that…

1) If you can prove (using QM) that the probability of a photon arriving at a particular image from the “wrong” pinhole is 50%, I would withdraw my claim.

…is likely to meet with success. Firstly, there is no necessity for this value to be 50%, as your measurement of the interference pattern is not perfect. Secondly, I don’t believe that this is even a question that can be answered using QM. QM is decidedly unconcerned about the origin and path of particles, only amplitudes and probabilities can be determined.

I could calculate the conditional probability of a photon being detected at the upper detector given that the upper pinhole was both open and closed (with the lower pinhole always open), and could show that this conditional probaility was higher when the upper pinhole was open. In a naive way you could then try to assign this discrepancy to amplitude arriving from the upper pinhole. But, that’s probably the best you can do.

I find it hard to see a way that you could prove that the measured photon came entirely from one pinhole. I would imagine that all such methods would destroy the interference pattern and ruin the experiment. Which just seems like consistency to me.

Keith

08/17/05 @ 09:47
Comment from: afshar [Member]

Dear Keith,

You say: “This demonstrates that in the original image plane there was a spatially separated superposition of wavefunctions, which is something you disputed earlier.”

You are misrepresenting what I said. I never denied that the mutual spatial coherence between the wavefunctions ending up in each image is lost, just that it cannot be MESAURED in the image plane, because you need to show interference fringes to show such mutual coherence. Any discussion of Complementarity must involve measurements. In the image plane the measurement cannot bring out the coherence or phase information, beacuse there are no interference fringes observable there.

You say: ” I don’t believe that this is even a question that can be answered using QM. QM is decidedly unconcerned about the origin and path of particles, only amplitudes and probabilities can be determined.”

This is completely wrong, and I am frankly quite amazed that someone who claims to have studied physics would say such a thing! In QM, the Hamiltonian, (or the Lagrangian if you like QED) determines the unitary evolution of the wavefunctions. These operators have built-in conservation laws (energy, linear and angular momentum etc.) It is the conservation laws that give us the ability to say for example, that a photon measured right in front of a pinhole must have come from that pinhole, otherwise the conservation law of linear momentum would be violated if we say it came from the other one.

Since you did not answer my 2nd question “2) If you do not like the above, then please let me know that in general what kind of evidence would satisfy you that a particular photon went through a particular pinhole, and then I’ll discuss the problem using that method.” here is the gold-standard, and universally accepted response:

ALL MEANS OF DETERMINIGN WHICH-WAY INFORMATION INVOLVE AT LEAST ONE CONSERVATION LAW WITHOUT EXCEPTION. This is extremely important to understand, without which the entire discussion on Complementarity is meaningless. If you do not agree with this, then you do not understand quantum mechanics, which is used daily to calculate high energy particle physics data, not to mention the humble Compton scattering!

I suggest that you read my paper, as well as the references I have made to John Wheeler’s works. John talks about which-way in the images very clearly and his view on this issue is exactly the same as mine (and any other expert in the field including some of my critics such as Unruh …) Issues involved are quite subtle and if you rather like to use equations and not ask questions, then this topic is not something you should dabble in. Hundreds of the greatest physicists have spent their lifetimes to clarify what is meant by Complementarity, which-way information, intereference observables, etc., and your above comments only clarify that you indeed like to “Shut up and calculate,” which is an immediate show stopper!

Regards

08/17/05 @ 10:40
Comment from: Keith [Visitor]

Dear Afshar,

Thanks for expanding a bit on your ideas. I am slightly of the “shut up and calculate” variety, but that’s mainly because I think people make too much of the philosophical implications of QM. Notwithstanding this, I do appreciate the need for consistency, and I do think it is very worth our efforts to find flaws and contradictions in accepted scientific theories and principles.

I’m interested in the alternate viewpoint you put forward regarding the time evolution of the wavefunctions.

Are you saying that because

|psi(t)> = U(t)|psi> = U(t)|psi_1> + U(t)|psi_2>=|psi_1(t)> + |psi_2(t)>

(where |psi> is the whole wavefunction, |psi_1,2> are the parts of the wavefunction coming from each pinhole, and U(t) is evolving the wavefunctions in time) and since at the detectors the wavefunctions are spatially separated sufficiently such that,

=0

then you can say with certainty that the photon detected at the detector corresponding to pinhole 1 came from pinhole 1.

Keith

08/17/05 @ 11:37
Comment from: Keith [Visitor]

=0

bra(psi_2(t)|psi_1(t)>=0

but there is some formatting problem

08/17/05 @ 11:40
Comment from: Quantum Mirror [Visitor]

Kieth said:

“So, you are saying that you support Afshar’s conclusions because you are unhappy with the fundamentals of QM, and have never managed to get your head around the implications of the archetypal two-slit experiment.”

You have put more words in my mouth here than a preacher paraphrasing Jesus. You obviously don’t want or need my my input in this discussion or you would not distort the meaning so much. Your confusion about QM may stem from your inability to grasp the meaning in a sentence. Such a lack of perception is a big problem in understanding quantum physics. Good day to you!

08/17/05 @ 12:01
Comment from: Quantum Mechanicast [Visitor]

Hello, i am a year 12 student studying afshars experiment and i am having issuses comprehending with it, i dont particularily think that geek Danko knows what he is talking about and should butt out of this, as for the rest of you, i dont particularily think this is a debate nor that you will come to a universal conclusion so cool it…If anyone could give me a brief run through of what happens in this experiment id b appreicative thanks heaps in advance

08/17/05 @ 22:17
Comment from: Quantum Mirror [Visitor]

“Are you saying that because

|psi(t)> = U(t)|psi> = U(t)|psi_1> + U(t)|psi_2>=|psi_1(t)> + |psi_2(t)>

(where |psi> is the whole wavefunction, |psi_1,2> are the parts of the wavefunction coming from each pinhole, and U(t) is evolving the wavefunctions in time) and since at the detectors the wavefunctions are spatially separated sufficiently such that,

=0″

NO!

08/18/05 @ 04:07
Comment from: Danko Georgiev [Visitor]

Dear Kieth,

i have seen somewhere you say “Danko does not know what he is saying", and I had no time to read all of your comments. But I think you can discuss the Afshar experiment with me by e-mail, so I think you will immediately change your opinion about the imporance of my work. The reason why I have not yet published official reply to Afshar is that I am in a process of finalizing one project that needs a lot of mathematical modeling.

Now in order to grab your attention I will discuss a simpler version of an experiment with double lens, and then I will ask you several questions whose answers are obvious, and I hope you will understand the general principle that I am talking about.

Now suppose you have double slit in the focal plane f1 of a lens L1, and you have a lens L2 focused on the f2 plane of L1. You have classical 4f system in which you have:
object-f-L1-f-f-L2-f-image.
As Afshar may insist there should be “which way” info in this setup.

Alas this is wrong. The L1 performs Fourier transform (Y) of the double slit input (X). This function f(X)->Y is surjective, but it is not injective, therefore it is not bijective. The simple fact is that each element x of X is mapped onto every element y of Y. So this is “holographic transform” and you don’t have bijection. The second lens L2 perform another “holographic transform” [inverse Fourier transform] that is again surjective but is not bijective. Since L2 applies the inverse function f^-1 of f you get back the set X, but YOU CANNOT SAY that you had bijective self-mapping x1->x1, x2->x2, …, xi->xi, because what you actually had done is applications of two consequent surjective functions f and f^-1 that were not bijective.

I think my example is showing clearly that there is no which way in this doeblelens setup, but Afshar says the opposite. The same mathematical principle can be generalized for the original Afshar’s setup - you cannot have interference [surjective, not injective function] and finally have which way info [that assumes series composed ONLY of bijective functions].

Best,

Danko

08/18/05 @ 05:29
Comment from: afshar [Member]

Dear Keith,

It seems that you have abused the formalism a bit, but I think I understand what you mean. The wavefunctions in the image plane do not interfere in the spatial domain, and each are the unitary evolution of the initial Psi_1 and Psi_2 due to the linearity of the Schrödinger equation and the operators. You really have to read my paper, and may also wish to take a look at a good QM textbook, e.g. Quantum Mechanics by N. Zettili, pp. 157-204, especially section 3.7 on Symmetries and Conservation Laws, where you can find a formal treatment of the topic without an abuse of the formalism!

Dear Quantum Mechanicast,

I am glad to see you and your generation of smart kids tackling longstanding problems in physics. My experiment concerns wave-particle duality contained in Bohr’s Principle of Complementarity. Search Complementarity and Afshar Experiment in Wikipedia to get a better understanding, but you really have to study QM at the post-graduate level to fully appreciate the experiment and its consequences. As you can see, even Nobel Laureates are having trouble!

Dear Danko,

I have made my and other experts’ opinion regarding your “ideas” quite clear in the past. IF and WHEN your paper gets published, your arguments MAY merit further response.

Regards.

08/18/05 @ 08:51
Comment from: PCMF [Visitor]

Prof. Afshar, thanks for your last answer. I have another question: with the wires
placed, if only pinhole 1 is open you see a flux reduction at detector 1′ compared
with the situation without the wires, right? Then you open the other pinhole 2 and that
same flux at 1′ is increased so that now you have an almost perfect image at 1′, right?
Do you agree that those additional photons arriving at 1′ must be coming from
pinhole 2? If not, where are they coming from since the only “new source” of
photons is pinhole 2? If you accept this reasoning it must be true that there are
photons from pinhole 2 arriving at detector 1′ and therefore you don’t have perfect
which-way information. Regards, PCMF.

08/18/05 @ 16:29
Comment from: afshar [Member]

Dear PCMF,

You said: “Do you agree that those additional photons arriving at 1′ must be coming from pinhole 2?”

NO! Make the following changes in your above argument: replace 1 with 2, and 1′ with 2′ and vice versa, keeping in mind that the total photon flux from both pinholes is a fixed amount. Think a little…

Now, according to your argument, 1 becomes the source of extra photons for 2′ and 2 becomes the source of extra photons for 1′, but when both are open, ALL photons arrive in the images. But we know that the amplitudes for the scattered photons cancel out at the wires, because they are in the dark fringes. The possible source of reduction in which-way information, namely the scattering by the wires, vanishes and hence the argument for the case when just one pinhole is open, no longer applies when both are open. IF THE INITIAL SOURCE WERE NOT COHERENT, THEN YOUR ARGUMENT MAY HAVE WORKED, BUT THEN AGAIN IN THAT CASE, THE TOTAL PHOTON FLUX DOES NOT GET BECK TO THE “NO WIRES” LEVELS WHEN BOTH PINHOLES ARE OPEN, THE BLOCKAGE WOULD STILL CONTINUE REGARDLESS OF WHETHER ONE OR TWO PINHOLES ARE OPEN.

Let me know if you need further explanation.

Regards.

08/18/05 @ 19:52
Comment from: Keith [Visitor]

Dear Prof. Afshar,

Sorry if I abused the formalism a bit in your eyes, but I did get across the idea that I intended. You said,

“The wavefunctions in the image plane do not interfere in the spatial domain, and each are the unitary evolution of the initial Psi_1 and Psi_2 due to the linearity of the Schrödinger equation and the operators.”

There is a problem here. The time evolution operator is not linear. I.e. if you evolve psi_1 and psi_2 separately you get a different answer than if you evolve them together (as psi_1 plus psi_2). This calls into question whether you can assign a history to a particle by applying the evolution operator in reverse. It therefore casts serious doubt on your assertion that perfect which way information is gained on detection of the photon.

I’m not convinced that you can use the idea of a propagator to keep track of which bit of wavefunction is which, especially when they have interfered. The more you think about it the less sense it makes. I think this is the flaw in your argument.

This backs up my statement that only conditional probabilities can be determined. For instance if you detect a photon right in front of a pinhole it is not “forbidden by a conservation law” to have come from the other pinhole, it is just extremely unlikely, and the probability can be calculated.

Morgan

p.s. I have read your paper, and there is no discussion of your experiment in terms of propagator ideas.

08/19/05 @ 04:45
Comment from: afshar [Member]

Dear Keith,

You said: “it is just extremely unlikely, and the probability can be calculated.”

That is exactly what is meant by which-way information K. The closer K is to one, the better the which-way information. The inequality K^2+V^2 lessthan=1 embodies Complementarity, and it has been shown in my experiment to be K^2 + V^2~=2.

Please read the references in my paper to the theoretical derivations of the above inequality to appreciate what is going on. In physics, we never talk about absolutes, because they are unattainable experimentally. If you can attain a 99.9% accuracy for your which-way information, you should get a completely washed out interference pattern with a negligible visibility…

You said: “I’m not convinced that you can use the idea of a propagator to keep track of which bit of wavefunction is which, especially when they have interfered.”

Well then, in that case please go ahead and write a paper that would challenge at least 20 papers by great physicists who have derived the above inequality, not to mention Bohr, Heisenberg and Einstein. You may find Bob Griffiths’ book “Consistent Quantum Theory” useful in appreciating the issue of complementary observables.

Best of luck!

08/19/05 @ 05:57
Comment from: Keith [Visitor]

Dear Prof Ashar,

I can’t say I’m happy with your use of the inequality V^2+K^2 is less than or equal to 1. This is an equation derived in the context of experiments with destructive measurements of the interference pattern, which yours is not.

Consider this: What happens as the thickness of the wires goes to zero? Your conclusions are entirely unaffected. You can still assign a perfect measurement of the interference pattern even if the wires are infinitesimally small! They might as well not even be there.

The reason this experiment works is because the wavefunction evolves, untouched, as a superposition of contributions from both pinholes. Only when a destructive measurement takes place does the wavefunction collapse. At this point it is impossible to assign a pinhole to the measured photon, as it was necessary that the wavefunction have components from both pinholes in order to get past the wires with sufficient intensity. This is related to the ideas of projection and non-linear propagation that I talked about earlier.

The photon had to have gone through both pinholes.

Morgan

p.s. Thanks for discussing this with me (its just a shame we can’t agree), and good luck in your future research. I hope you come up with many more thought-provoking, and potentially ground-breaking ideas.

08/19/05 @ 07:44
Comment from: Quantum Mirror [Visitor]

Kieth said:

“Consider this: What happens as the thickness of the wires goes to zero? Your conclusions are entirely unaffected. You can still assign a perfect measurement of the interference pattern even if the wires are infinitesimally small! They might as well not even be there.”

The wires are there to indicate that interference is present. A test if you will of interference. If there is no interference the wires will be sparkling and the graph of the CCD will show a reduction in the amount of light returned. The wires going to zero what would that indicate? This is like telling someone they don’t need eyeballs to see.

08/19/05 @ 09:45
Comment from: afshar [Member]

Dear Keith,

You said: “You can still assign a perfect measurement of the interference pattern even if the wires are infinitesimally small! They might as well not even be there.”

No! You seem to be missing the whole point of my experiment. The wires DO tell us a story about what is NOT there. Without the wires, akin to watchful guard dogs in Sherlock Holmes’ story, the case of “the dog that didn’t bark", I cannot tell that there is a dark fringe where wires are placed. A new kind of measurement is taking place here which I fully explore in my upcoming PRA paper. I have touched on it in section 3 of my original paper, if you like to learn more.

Regards.

P.S. Thanks for the kind p.s.!

08/19/05 @ 13:37
Comment from: PCMF [Visitor]

Dear Afshar, I do agree with your answer that my (sort of semi-classical) reasoning is faulty; let me just rephrase it a little:

Question: “Do you agree that those additional photons arriving at 1′ must be coming from pinhole 2?".

Answer: “No, they are coming from pinhole 1 but now they do manage to pass through the wires without absorption".

Thank you.

PCMF.

08/19/05 @ 13:49
Comment from: afshar [Member]

Dear PCMF,

Therein lies the crux of this seemingly paradoxical experiment. It is very suggestive of other experiments, a few of which are currently being conducted. I will leave the description of these experiment to occasions after their finalization.

Regards.

08/19/05 @ 14:06
Comment from: Keith [Visitor]

One last thing,

I seem to have not explained the wires going to zero thing adequately, I feel the need to try again.

The inference of the presence of an interference pattern is based on the difference in flux of photons with and without the wires in place. Assuming the wires are sufficiently thin for your experiment to work to begin with, halfing this thickness would half the difference between the two observed fluxes. If your experiment is accurate enough (which I believe it easily is) then you could still measure this difference, and still draw the conclusion that the difference is due to the presence of an interference pattern.

You could carry on reducing the thickness of the wires in this way and (at least theoretically) still measure a difference between the two fluxes, and still infer the interference. The limits on this procedure are practical, and not some QM limitation, hence my assertion that you could make the wires infinitesimally small, and still measure the infinitesimal difference in fluxes, and therefore still come to the conclusion that you have made a perfect measurement of the interference pattern.

This is clearly an issue which you would have to address in that upcoming PRA paper, if you claim to have a good understanding of this type of measurement.

Morgan

08/21/05 @ 22:36
Comment from: Quantum Mirror [Visitor]

Kieth said:

“You could carry on reducing the thickness of the wires in this way and (at least theoretically) still measure a difference between the two fluxes, and still infer the interference. The limits on this procedure are practical, and not some QM limitation, hence my assertion that you could make the wires infinitesimally small, and still measure the infinitesimal difference in fluxes, and therefore still come to the conclusion that you have made a perfect measurement of the interference pattern.”

What would be the logical purpose of such an procedure? The wires are there for a specific purpose. They are there to tell us if interference is happening in the experiment. To reduce or to remove them is not logical. You are changing the purpose of the wires into some kind of zeno quantum voodoo regulator with confusion dipstick guaranteed to retain the mystery of quantum physics.

08/22/05 @ 06:36
Comment from: Keith [Visitor]
08/22/05 @ 22:15
Comment from: Keith [Visitor]

That was the sound of me banging my head against a wall.

08/22/05 @ 22:15
Comment from: Fred Kiani [Visitor]

Hi guys,

I got used to check this blog everyday and had no luck finding a new post! What happen to everybody all of sudden. Dear Prof. Afhsr and Quantum Mirror, please updat us with any news (good or bad).

best regards,

Fred Kiani

09/07/05 @ 05:00
Comment from: Quantum Mirror [Visitor]

R. E. Kastner has revised the paper entitled:

Why the Afshar Experiment Does Not Refute Complementarity

It seems to be a complete rework of the paper. I have not had time to compare the two or to read more than a couple of pages of this paper, but what I did read was completely different. I skimmed some of the paper and noticed she went to a lot more trouble in explaining her arguments in some spots. She still claims to know the mind of Bohr and what he would think about this experiment. How many other physicists would claim to know what Bohr would think? I know Einstein said: “Despite the expenditure of much effort, I have been unable to obtain a clear understanding of Bohr’s principle of complementarity”
I do not think anyone can say for sure what Bohr would think about any physical system. But this is also an opinion and not a physical interpretation.

http://arxiv.org/PS_cache/quant-ph/pdf/0502/0502021.pdf

09/09/05 @ 04:26
Comment from: Peter Tanguay [Visitor]

all,

I have taken a quick look at Kastners paper. This paper is much better presented than the first. It compares the Albet, Aharanov, and D’amato (AAD) spin experiment concernig horizontal and right cirlcular polarization to IP and WWI as commuting variables.

I think the defining difference is that changing polarization uses a polarizing medium which exerts an electric field on to the light. AAD is not a non-destructive test.

Additionally she maintains that because the photon went through both slits, its’ WWI cannot be defined. this is akin to saying that because bohr is correct then Afshar cannot be.

There is NO proof of the photon existing in transit. There is simply a quanta of energy observed at emmision and observed at absorption.

Afshar in a previous post has expressed the Dirac view of a State vector which has no physically going through both slits. this avoids inconsistent statements such as the photon went through both slits.

I beleive TI has given Physicality to the state vector through the advanced and offer waves. I see the Afshar experiment metaphorically more like the Wheeler delayed choice experiment with non destrictive measurement of IP.

Peter Tanguay

09/10/05 @ 03:58
Comment from: quantum enforcer [Visitor]

Is the peer review process complete as yet Prog Ahshar ? Proof of the experiments validity will come through peer review but as yet this work has yet to be published. If the experiment is quantum mechanically consistant then publication will surely go ahead.

09/11/05 @ 06:07
Comment from: Quantum Mirror [Visitor]

Dear QE

The paper has been published see:

http://irims.org/blog/index.php/2005/03/13/questions_welcome_1#c655

Dear Peter Tanguay

Nice review and well put!

09/11/05 @ 09:08
Comment from: Peter Tanguay [Visitor]

Dear Quantum Mirror,

thanx for the kudos.

Pete

09/12/05 @ 05:12
Comment from: Quantum Mirror [Visitor]

Dear all:

Here is a very interesting preprint:

http://arxiv.org/ftp/quant-ph/papers/0312/0312026.pdf

What Is A Quantum Really Like?

Shahriar Afshar provided stimulating feed-back and helpful criticism.

Dear Asfhar
If you really know the person who wrote this, tell them to take that background out of the PDF. I finally had to cut and paste it to notepad to read it.

09/12/05 @ 12:18
Comment from: Quantum Mirror [Visitor]

Dear afshar
Thank you!

09/12/05 @ 13:57
Comment from: quantum enforcer [Visitor]

I need a few questions about this experiment answering please. Does the uncertainty principle in a two slit experiment tell us that we cannot see wave (postion) and particle (momentum) behaviour simultaneously or is that how the copehnagen interpretation see it ? If so then if Prof Afshars experiement allows both types of behaviour to be determined simultaneously then is not the uncertainty principle violated as we can see both position and momentum at the same time.

09/13/05 @ 12:31
Comment from: Quantum Mirror [Visitor]

Dear QE

The uncertainty principle is not an all or nothing measurement. It states that the more we know about position the less we can know about momentum and vise versa. It does not restrict some measure of both at the same time.

09/14/05 @ 06:48
Comment from: quantum enforcer [Visitor]

But I thought that Bohr used the uncertainty principle to explain his principle of complementarity in that waves and particles are not able to exist at the same time in the same two slit experment. In fact ALL subsequent expleriments on the two slit theme until Afshars have no reason to call into question Complementarity. A lot of these experiments were subtle involing parametric down conversion, beam splitters half silverd mirrirs and the like but no matter what they did to obtain the necessary which way info in single photon experiments they failed to do so and QM predicted it would be so. So howcome Prof Afshar has found a way, surely this should run counter to the math of QM ? I am suprised that it does not but why does it not ?

I read a review of QM recently regarding the non local ability of QM. Apparantly in two or more quantum entity experiments entanglement is the stronger principle and both Borh and Einstein were in fact correct, so why should ultimately entanglement be right ? After all Schrodinger did not makes up his cat experiment nothing.

09/14/05 @ 12:40
Comment from: quantum enforcer [Visitor]

Borh and Einstein were in fact INCORRECT. Typing error sorry.

09/14/05 @ 12:41
Comment from: afshar [Member]

Dear quantum enforcer,

Heisenberg’s uncertainty principle (HUP) is fully upheld by my results. As light emerges from each pinhole it is spread out due to diffraction. The extent to which this spread in momentum takes place is inversely proportional to the diameter of the pinhole in accordance with HUP. Each image also has the exact same relationship in terms of its radius and momentum spread again obeying HUP.

While Bohr used HUP to defend his principle of complementarity (PC), he claimed that it is HUP that is the result of his PC and not the other way around. It was shown theoretically by Scully et al. and later verified by Rempe and Dűrr et al. that PC is not always enforced by HUP. In their analysis entanglement with the measuring device of which path marker does the trick. In my experiment there is no entanglement involved for the measurement of interference and thus PC fails in this heretofore uninvestigated measurement technique. This issue is extremely subtle and takes many thought-hours to figure out. It took me 18 years for instance! For more details wait for my PRA paper.

Regards.

09/14/05 @ 16:03
Comment from: Quantum Mirror [Visitor]

Dear QE

quantum mechanics is very complicated and confusing to the point of distraction. Any review you read you can find the opposite review somewhere else in the literature. This preprint proves copenhagen was based on a flawed probability theory:

http://arxiv.org/PS_cache/quant-ph/pdf/0509/0509089.pdf

These are some passages from What is a Quantum?:

http://arxiv.org/ftp/quant-ph/papers/0312/0312026.pdf

In light of the above, self-interference must be ruled out. None of its major implications were able to survive experimental assessment. Firstly, photons were shown beyond reasonable doubt to have well-defined single paths during double-slit interference. Secondly, they were proven to interact only within limited intervals from each other. Finally, interference revealed itself as a real phenomenon, independent from abstract informational processes. On the other hand, this conclusion is at odds with several major developments in modern quantum mechanics. In particular, it is incompatible with the hypothesis of quantum erasure, which is widely believed to explain many quantum processes, including self-interference. Consistency with quantum erasure has been reported in many experiments. Therefore, it must be given immediate attention, in order to avoid an interpretive inconsistency.

The status of quantum erasure, in terms of experimental support, is not any stronger than that of self-interference, and therefore it can neither confirm nor predict it. The greater the number of experiments considered, the harder it is to defend non-realist models.

The hypothesis of particulate wave-producing photons leads to interesting connections with other concepts in modern physics. It is compatible with a brane-world scenario, in which localized particles engage in mediated interaction. It explains the frequency of de Broigle matter waves in terms of corresponding numbers of elementary wave-sources, detectable as macro-particles. It also provides a classical mechanism for the operation of Maxwell’s equations, by showing that electric and magnetic components are produced simultaneously in discrete steps by photons. Specifically, electric fields must be produced as longitudinal 3D waves, in order to explain the inverse square law and the role of phase coherence during interference; magnetic fields would be simultaneously produced as 2D transverse waves, which predict the features of polarization. The manipulation of fields must be due to the effect of some particles on other particles. Magnetic and electric fields are not expected to generate each other in vacuum, in the absence of matter. Furthermore, this approach is in good agreement with Huygens’ model of wave propagation. It also provides a natural explanation for the directionality and quantized nature of electromagnetic waves.

As you can see this has good arguments against the very principles of quantum mechanics. This has not been published and will be at the bottom of the list for most journals to print. I think you must keep an open mind to all the arguments in QM and not take any rules as law.

09/14/05 @ 18:29
Comment from: quantum enforcer [Visitor]

Guys

Thanks very much for the replies, it means a lot.

And if I may ask further…

If you cannot tell which way the particle has gone then you get a wave pattern registered at the detectors. In your experiment Prof Afshar at first you pass light from the pinholes to a lens which focuses light onto two mirrors and on to two detectors. As you can tell which path/way the light has gone you have no interference pattern to report because their should not be one (according to Complementarity or quantum math itself though I am not sure ?). This means that you have collpased the wave function and only photons are shown registering at the detectors, indeed at this moment you experiment has no way of showing waves.

You then do your wires trick with one hole closed and hence making it photon traffic only (as you know the path for certain now) and you are telling me that the effects the detectors are experiencing are photons that are being blocked/deflected (defracted) away from the detectors. You then release the other path nd you still see only photons because you have which path information. But wait the images at the detectors are restored to normal information levels telling us that we must also be seeing the wave nature of light at the wires as they are now not blocking light but still registering perfect photon cound at the detectors (we are arn’t we ?) and only waves interfere with themselves.

You have also done the experiment with single photon of light and the results are exactly the same. Are you in someway infering that the waves are there rather than directly viewing them and it is this that sets the experiment apart from others ?

Is your experiment showing a deeper reality, namely that quantum entities can be anything you ask them to be if you can only tease it out of them and for decades no one had been able to thus duping us all into thinking that no matter what was sone experimentally only one behaviour was available at any one time.

You are saying that WWI has no bearing on type of behaviour as previously thought if you can get the right experiment setup.

09/15/05 @ 10:14
Comment from: quantum enforcer [Visitor]

just one more thing…

Looking around at other single photon two slit experiments that attempt to keep the interference pattern whilst measuring the slit that photon takes I can see that they are all setup in order to measure waves (hence the interference pattern) and then they attempt to find WWI. Prof Afshars experiment on the other hand measures photons that provide WWI thus allegedly forbidding wave behaviour, however waves are inferred via restoration of the image at each detector.

could it be that experiments set up for particle detection first rather than wave is the difference between this any all the other two slit experiments. After all there has to be a difference I would imagine ?

09/17/05 @ 02:23
Comment from: afshar [Member]

Dear quantum enforcer,

As I have mentioned in my paper (see section 3), ensemble properties such as coherence and interference can only be measured nonperturbatively PRIOR to particle properties. That is indeed one of the major differences between my experiment and all others thus far.

Regards.

09/17/05 @ 06:21
Comment from: Danko Georgiev [Visitor]

Dear prof. Afshar,

I personally am still wondering why you resist the obvious fact that your interpretation is WRONG. As Keith said if you reflect back the two photons, instead of detecting then at D1 or D2 you admit there will be interference. This shows that there is no which way info.

And you still insist that there is “perfect which way info” and all that stuff. If you really undertand the essense of my argument you will see that Keith is right, because he says what I have repeatedly posted.

SUPPOSE that the photon at D1 really brings info of slit_1 and suppose that the photon at D2 really brings info about slit_2, then these two wavefunction are not coherent and THERE MUST BE NO INTERFERENCE! So, you, Motl, Unruh, Drezet, et al. insist on obviously wrong thesis.

Actually the Keith’s proposal is variation of my proposal to observe out-of-focus, etc. The Drezet’s pseudo-objection is that “these are not the same photons …", but I will not comment any more on that.

Dear Keith, I just want to tell you that your proposal just shows that there is no which way info as wrongly claimed by Afshar.

Danko

09/20/05 @ 13:19
Comment from: Quantum Mirror [Visitor]

Yet another mania episode in the bipolar life of Danko! Go take a pill!

09/21/05 @ 01:33
Comment from: quantum enforcer [Visitor]

Dear Prof Afshar and others

Looking at the experiment again I need to ask another question. As the experiment is setup for particles what exactly constitutes a particle ? I mean can a lens diffract a particle or will a lens only work with waves ? Surely a wave will produce the same image at the detector as will a particle and hence how do we know that even though a photon is emitted by the laser and detected by a detector that it travels as a particle. Could it not travel as a wave but leave and arrive as a particle in this case ?

10/06/05 @ 07:11
Comment from: Quantum Mirror [Visitor]

Dear QE

Your questions indicate a misunderstanding of the very basic ideas on how photons are emitted and absorbed by atoms. Here is a good link to help you understand and better phrase your questions where they are more easily answered.

http://www.thespectroscopynet.com/Educational/wave_particle_duality.htm

It is all about balancing the amount of energy that is contained in atoms. Here is a link that may help you understand how photons are emitted or absorbed:

10/08/05 @ 17:00
Comment from: quantum enforcer [Visitor]

Dear QM

From reading the articles I would suggest that you cannot talk about photons with refering to waves. From the second article:

emits photons with the characteristic wavelengths corresponding to the transitions between different energy levels of the atoms or molecules in the gas.

Do particles have wavelike properties ?

10/09/05 @ 11:22
Comment from: quantum enforcer [Visitor]
10/09/05 @ 12:11
Comment from: Quantum Mirror [Visitor]

Dear QE

I still do not understand your question. The whole subject of the double slit experiment is wave particle duality. The understanding of a photon is the interpretation of the energy it carries as frequency (color) and amplitude (strength) which is absorbed by a atom in a ccd, an eyeball, photographic film or as heat when it has reached it’s destination. How it exists after it is emitted and before we detect it can only be described as wavelike in how it is interpreted in experiments where it goes through slits or pinholes and exhibits these wavelike properties.

10/11/05 @ 18:50
Comment from: Joshua Jones [Visitor]

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10/11/05 @ 21:02
Comment from: joshua jones [Visitor]

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10/11/05 @ 21:03
Comment from: charles anderson [Visitor]

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10/11/05 @ 21:05
Comment from: quantum enforcer [Visitor]

Dear QM

So where is the controversy over wave particle duality then if light (in this case) travels as waves but arrives and departs as particles. Is that the final conclusion of Prof Afshars and others work then fine but seeing as how many many experiments have attempted to reveal whether light is waves or particles but always ended up collapsing the wave function revealing light to be either/or and not both hence complementarity.

I would suggest that now that Prof Afshar has revealed this duality in a single experiment that ALL experiments should be able to show duality. One experiment hardly makes duality a law and I wonder regarding all the other experiments that failed to do what Prof Afshar has shown and why they failed ?

Complementarity has not lasted so long on a whim, it was allegedly founded on many many experiments all failing to show otherwise until now.

This is what concerns me.

10/12/05 @ 02:00
Comment from: Keith [Visitor]

The difference between this experiment and those other ones is the non-destructive nature of the (attempted) measurement of the wavelike nature of the light. Complementarity clearly holds for destructive measurements (it’s a necessary consequence of the fundamentals of QM, and works in every such experiment ever undertaken), but not necessarily for this non-destructive inference of an interference pattern.

I think that “measurement” is another one of those words which has acquired a stricter scientific meaning than the common usage, hence the strong reaction of some in the scientific community to Afshar’s conclusions. The response is that Afshar cannot possibly have “measured” the interference pattern as this refutes complementarity, which is self-evidently a correct principle. However, even though he hasn’t “measured” the interference pattern perhaps he has infered it in some way.

Even though his experiment does not do anything that is unexpected, or that undermines the principles of QM, I do hope that Afshar can manage to publish a paper which explores this subtlety.

Morgan

10/12/05 @ 08:44
Comment from: quantum enforcer [Visitor]

Non destructive in what sense ? How were the other experiments destructive in that gaining WWI collapses the wave function without violating the HUP ?

I have no issue with Complementarity being wrong myself as I would argue against the special role of any seemingly conscious observer in order to collapse the wave function.

10/12/05 @ 11:49
Comment from: Keith [Visitor]

Non-destructive in the sense that the wave function passes the place where the interference pattern is inferred entirely in tact. The other experiments involve a destructive measurement as they partially collapse the wavefunction.

Complementarity does not require the presence of a conscious observer, nor does collapse of the wavefunction.

10/12/05 @ 22:47
Comment from: quantum enforcer [Visitor]

No complementarity does not require the presence of a conscious observer but it was thought that it did back in Bohrs day when it was originally formulated (Schrofingers Cat) or else the 50 or so laymans books on QM I have read must all be wrong.

So what subtle feature of Afshar experiment can account for an act of measurement so subtle that we do not see the collpase of the wave function as opposed to an act that does ? Sounds to me that Afshars experiment reveals that light is both a wave and a partcile at the same time but does it in a way that is non destructuve (via the wires I presume) whilst all other methods have used polarisation. Is Prof Afshars experiment a special case rather than the norm ?

10/12/05 @ 23:40
Comment from: afshar [Member]

Dear all,

I will be giving a couple of lectures at the Canadian Perimeter Institute next month (the exact date will be announced later.) The focus of the talks will be “nonperturbative measurements” in QM, and how it is revealed in my experiment. If anyone is nearby, you can attend the talks, should you be interested. As soon as I get info. on the dates and other logistics I’ll let you know.

Regards.

10/16/05 @ 23:37
Comment from: quantum enforcer [Visitor]

Dear Prof Afshar

For all those who cannot make it to Canada for your talk would it be possible for your to post a critique of your talk here at all ?

10/18/05 @ 04:55
Comment from: afshar [Member]

Dear QE,

I may be able to record and post the talks here, or on my web-page. The issues will also be covered in a paper which will be posted as well. As for critique of my work, I leave it to the capapble minds of the physics communinty!

Regards.

10/18/05 @ 08:14
Comment from: quantum enforcer [Visitor]

Dear Prof Ashar

Well to be honest I would just like some more understanding of the term nonperturbative measurments and why that is for some reason the reason why your experiment differs from all others. Is it because you are somehow revealing the wave nature of light by not measuring as the “wires” only show the fact that light also has to be acting as a wave in order for the effect that we see (the image restored) to be explained ? I can only say this because you are detecting particles in the standard way.

Now if I put a polariser in front of a ligth wave, how is that I am using a “perturbative measurement” instead. Have I disturbed the light in some measureable way, ie polarisation effect ?

Is it different from puting wires in the way ?

kind regards

10/18/05 @ 10:25
Comment from: afshar [Member]

Dear QE,

You said: “Now if I put a polariser in front of a ligth wave, how is that I am using a “perturbative measurement” instead. Have I disturbed the light in some measureable way, ie polarisation effect ? Is it different from puting wires in the way?”

Every time you place a polarizer in front of a beam of light its intensity is reduced according to the Malus’s law. Most critically, it is not a unitary evolution due to the resulting reduction in norm of the wavefunction(s): i.e. it is perturbative process. In contrast, the wires do not reduce the norm significantly, thus allowing the unitary evolution of the wavefunctions to continue. I hope this helps!

Regards.

10/18/05 @ 11:02
Comment from: quantum enforcer [Visitor]

Dear Prof Afshar

Thanks for the reply, I have never heard of Malus’s law and I am also suprised and slightly alarmed that many popular books and articles on QM never stated this fact prefering instead to state that the gaining of WWI is enough to collpase the wave function and proclaiming that as amazing in its own right (which it is of course in classical terms).

So are you suggesting that it is the “degree” of disturbance that tells us whether it is a nonperturbative or perturbative measurement ?

Once again thankyou for your time.

10/19/05 @ 00:42
Comment from: afshar [Member]

Dear QE,

Malus’s law is actually quite old (19th century) and can be found in any textbook on optics. A more modern version using the quantum mechanical formalism can be found here: http://arxiv.org/abs/quant-ph/9502028.

Regards.

10/19/05 @ 05:21
Comment from: Peter Tanguay [Visitor]

Dear Professor Afshar,

I have some ideas and questions regarding the wire size and its repercussions for measuring V.

As you have stated in your paper page 19 of the preprint, It is expected that the result can be improved upon by reducing the thickness of the wire size in the WG, yet maintaining the condition for opacity (e>>l), and increasing the resolution and sensitivity of the CCD’s

What would be the smallest or largest the wires could be, and still observe violation of complimentarity? I believe defining this in terms of n, or simply Rcoherent and R decoherent would help make your case clearer when presented with the argument brought forth by Motl.

At some point one might claim that V=1-e. When would that happen? There is a trade off to be defined between larger and smaller wires with regards to measuring the decoherent and coherent cases. As you have stated, this would also vary with the resolution and sensitivity of CCD.

Regards

Peter Tanguay

10/20/05 @ 05:45
Comment from: Quantum Mirror [Visitor]

Dear Peter Tanguay
The thing you must realize about Lubos Motl, he is a hotheaded egotistical idiot/savant. He is famous for this on all physics blogs. He will fly off the handle and post something completely nonsensical and irrelevant to the discussion at hand. If you will closely read his arguments you will realize he did not understand the experiment and had not fully read the paper when he made them. He is much to busy to be bothered with reading a paper, a book or an article he is bashing. Beside that he considers himself too much of a genius to be bothered with such mundane layman’s work as actually needing to read anything below the level of 15 dimensional string theory. Anything else he can just glance at and completely understand. Not! His arguments did not even relate to this experiment.

10/23/05 @ 08:55
Comment from: quantum enforcer [Visitor]

Dear All

Well the wires have to of a thickness so that they fit in the interference band completely othewise there would still be scattering of light would there not ?

Come on everyone we can all see that this experiment is a good one and has been shown to be correct. I await Prof Ahshars laymans book on what it all means for QM.

10/23/05 @ 09:40
Comment from: John Murphy [Visitor]

Regarding Malus law, surely the Afshar Experiment is very similar to “measuring” polarization when one has a-priori knowledge of the polarization state.

Both experiments involve a-priori knowledge and both require a statistical average over a large number of photons.

If one sets up an analyzer in alignment with a linearly polarized beam then one also has a situation wherein one makes a measurement without affecting the quantum state of the beam. The wires perform a very similar function, they do not form an observation in the sense that a photons position in the interference pattern is determined, they merely provide a null measurement or “denial” that is idenitcal to setting up an analyzer when one has a-priori knowledge of the incident polarization state. In a polarization measurement, a photon passing a polarizer only tells you that the incident state was not exactly aligned at right-angles to the analyzer.

This is a much weaker measurement than the direct detection of the photon at the slits then having it subsequently form part of an interference pattern. The Afshar experiment says nothing as to the truth or otherwise of this type of strong measurement that was at the center of the Bohr - Einstein argument.

It is well known in formal logic, that measurements that form a denial [like saying “it is not raining - weather” or “the photon was not here - wires"] do not constitute a full blown bivalent determination that can be the subject of boolean “true-false” analysis. Take a look at
“Logic States and Quantum Probabilities"; International Journal of Theoretical
Physics, Vol 35, No. 5, 1996.

10/24/05 @ 01:11
Comment from: afshar [Member]

Dear John Murphy,

A null measurement of V=0 tells us all we need to know to falsify an argument that predicts a V=0. In other words, in your example above, if we see it is raining, the “it is not raining - weather” statement is immediately nullified. Similarly, if a statement like PC predicts that there should be no interference, and thus there must photons incident on the wires; “the photon was not here - wires” is immediately sufficient to nullify the statement. That is exactly what this experiment accomplishes!

Regards.

10/24/05 @ 16:50
Comment from: Keith [Visitor]

Nicely put, John. I see where you are coming from.

The wires don’t deflect any photons because the experiment was set up not to deflect any photons at the wires. The null measurement of the wires tells us nothing we didn’t know already. The later measurement at the detectors is consistent with the null measurement. There is little else to say.

Morgan

10/25/05 @ 22:43
Comment from: quantum enforcer [Visitor]

Dear Keith

the null measurement at the wires tells us that you can see waves and particles at the same time in a two slit experiment.

Surely that is the point, to show up complementarity for what it is. An incorrect assertion.

10/26/05 @ 04:46
Comment from: Keith [Visitor]

Well, no. Complementarity clearly refers to destructive measurements, where it is self-evidently correct.

However, Afshar’s experiment does nicely dispel the myth that measurement of a particle collapses the path the particle has previously taken. His experiment is an example where it is extremely tempting to assign a path, but you really cannot.

Morgan

10/26/05 @ 08:28
Comment from: quantum enforcer [Visitor]

Ashars experiment only “infers” (non perturbative ?) waves is that what you are saying ?

Only a wave can interfere with itself and produce dark fringes that restore the image to almost its full intensity whilst at the same maintaining through the lens WWI/WPI. Is this not the case and if not why not ?

Schrodinger had it right with his cat paradox when speaking of complemantarity. Not everyone was enamoured of Bohr it would seem.

10/26/05 @ 09:57
Comment from: quantum enforcer [Visitor]

Amendment - when I say only a wave can interfere with itself I meant that only waves can produce interference.

10/29/05 @ 01:48

Dear Shahriar,

I wonder why there is no search result for you in arXiv. Could you please write for us the information of the details of your publications.

Thank you

11/11/05 @ 14:35
Comment from: Quantum Mirror [Visitor]

You can use: http://www.irims.org/quant-ph/030503/

11/13/05 @ 20:54
Comment from: Shannon Rowe [Visitor]

Dear Professor Afshar,

I would like to propose the following, even simpler, experiment which may be useful in further confirming your theories. Utilising a standard two-slit single-particle-at-a-time apparatus (ie a stock textbook setup, unmodified with the wires):

Step 1: Fire single particle while detectors are turned OFF.
Step 2: Turn detectors ON for a short period of time, do nothing, and then turn detectors OFF again.
Step 3: Repeat from Step 1, looping until sufficient particles have been fired to establish (or not) interference.

The idea is that the particles are always fired during an OFF cycle of the detector, with the detectors only turned ON and then OFF in between (never during) each firing in order to “flush” the experiment. According to regular quantum theory, as I interpret it, such an experiment should still produce an interference pattern because each individual particle is not actively being measured at the time it is fired, and according to complementarity, is allegedly interfering with itself.

If however, an interference pattern does NOT occur, then this opens up a whole new area of investigation along similar lines to your own findings. Were that to happen, one theory may then be that each particle is somehow tangibly affecting the progress of the next particle. Which would lead to the question: what IS interference, really? Maybe interference is NOT caused by a given particle’s wavefunction interfering with itself after all, as Copenhagen would have it, but is actually a result of some sort of lingering “quantum wake” trailing behind the previous particles that have passed through that same space. In other words, the interference could be due instead to a barely perceptible “wake” or “ripple effect” left behind in that region of space by the passage of previous particles - a wake that can be smoothed out or “flushed” somehow by, in this case, the flashing of the detectors. As a visual example, imagine the wash from a speedboat causing turbulence to affect any vessels following behind it. And since it’s hard to extend that analogy to include the flushing mechanism, to illustrate that aspect, imagine footprints in the snow being filled in by fresh snowfalls.

At any length, whether the above seems foolish or not, I would imagine that the experiment as outlined above would be rather easy for you to test in your lab, given the equipment you have on hand. I don’t recall having seen any other researchers consider the issue of wake causality, and I imagine such an experiment would still be valuable whatever the outcome. If the result was that it still produced the expected interference, then at least the assumption used in all two-slit experiments - that previous particles do not affect later ones, and that there is no causal lingering effect - could be successfully continued and to some extent verified. However, if interference is NOT present, then it would be one further nail in the coffin of complementarity, and a whole new can of worms would be opened, also adding a great deal more support to your conclusions.

Regards,
Shannon

11/17/05 @ 20:23
Comment from: Peter Tanguay [Visitor]

Dear Shannon,

Have you looked into the Wheeler delayed choice experiment? It sounds very similar to what you are proposing.

where is quantum mirror ?

Also What is the latest status on Afshars paper being published in PRL? Is it PRL A? etc.

Peter Tanguay

11/21/05 @ 02:12
Comment from: Shannon Rowe [Visitor]

Dear Peter,

Yes, I’ve already pored over all the material for Wheeler’s delayed choice, and also Scully and Drühl’s quantum eraser. You’re correct in that they are similar, but from what I’ve seen, those delayed choice experiments are more about “catching the particle in the act” by activating the detectors midway through the particle’s run. I’m not aware of any experiments so far that have attempted to establish whether there is some sort of interference causality that lingers over time between particles that can influence subsequent particles. It seems to me that there has always been an unverified assumption that only immediate spatial causality matters, and I believe this assumption needs to be challenged.

The generally held conclusion seems to be that experiments with singly emitted particles indicates that those particles must be interfering with themselves, via wave-particle duality, because such experiments have assumed that only one particle is present at a time, in a spatial sense. However, correct me if I’m wrong, when a more basic two-slit experiment is performed with a continuous stream of particles, it is then generally claimed that the interference in those cases is caused by the stream of particles from slit A interfering with those from slit B, ie normal wave pattern interference. So interference, according to theory, can come either from other particles passing through the slits in the stream variation, or from a single particle interfering with itself in the single particle variation. This is all, however, based on the assumption that interference must be occurring at a spatial level only - ie that the stream of multiple particles, or the spread-out wave of the single particle, are passing through the slits at nearly the same time and causing “real time interference". This logic strikes me as having omitted time as a possible variable.

What I would like to see tested is that assumption of spatial causality, to try to prove or disprove whether time causality might also matter. Because if interference is actually something that can linger within an experiment over a time duration as well, like the ripple of a stone thrown into a pond taking time to spread out and fade, then that would put the theory of single particle self-interference into question. One hypothesis that could arise from such a finding would be that maybe there is a “quantum wake” lingering behind each particle’s passage and influencing subsequent particles; this could then potentially negate the need to claim self-interference as the explanation for single particle apparent interference - it would then be equally plausible that the wakes from previous particles were causing the disturbance. Furthermore, the “flushing” of these wakes caused by the use of detectors might go some way towards explaining the measurement problem. The nature of such a hypothetical quantum wake is of course another matter entirely, and I do have further thoughts about what that would be, but obviously there’s no point waving theories around unless an actual experiment indicates that there is in fact something anomalous to explain.

Now this may all be just conjecture. Most likely there isn’t any such “lingering wake", and wave-particle duality will still hold firm as per the standing theory, but it seems to me as though this long-held assumption should at least be tested, if possible, because I haven’t seen any evidence that the notion of causality has been properly considered or disproved so far. The self-interference explanation has become accepted because it is the only logical explanation when you look at the findings from a spatial point of view only. But what if the issue of time (and quantum effects that linger over time) has to date been ignored? Professor Afshar’s findings that seem to defy the measurement principle certainly suggest that something is wrong with the Copenhagen model. Perhaps it is the inherent artificial laboratory nature of the two-slit experiment that has blinded us all to ticking off all the assumptions involved, and we have so far neglected the idea that time might be a factor. At any length, it is always good to re-examine and re-test all of our “concrete assumptions” with a fresh eye. This is why Professor Afshar’s work has been so valuable, in challenging some of those assumptions and finding their flaws.

Regards,
Shannon

11/21/05 @ 13:04
Comment from: afshar [Member]

Dear Shannon Rowe,

There is no doubt that single photons interfere with “themselves” and there is really no way that a photon affects another photon later on. Technically speaking, a coherent source cannot give you true “single” photons, but in that case, we use something called the coherence length of the photons to determine the flux below which the overlap between the two sequential photons is negligible. If your coherence length is small compared to the optical path of your experimental setup, you can easily achieve a condition in which at any given instant only one quantum of light is present in the system. In that case, you can say with a high certainty that the presence of two photons between subsequent detections is negligible (usually of the order of 10^-4).

So, to make a long story short, the “lingering wake” exists only at high flux where there is substantial overlap between the wavefunctions of photons, otherwise at low flux or short coherence lenghts (i.e. downconverted photon pairs) photons do not affect each other in the manner you discussed. This is well documented and is used everyday in the quantum optics labs.

I hope this helps!

Regards.

P.S. Papers are still under review!!!
For those interested, here’s the link to my talk at the Perimeter Institute:
http://www.perimeterinstitute.ca/activities/scientific/seminarseries/alltalks.cfm?CurrentPage=1&SeminarID=611

11/21/05 @ 21:27
Comment from: Peter Tanguay [Visitor]

Dear Afshar,

Good to hear from you.

What is the feedback from the reviewers? Can you comment? Is it close?

Peter Tanguay

11/22/05 @ 02:22
Comment from: Shannon Rowe [Visitor]

Dear Professor Afshar,

Thankyou for your explanation. It has helped to make things clear. I appreciate your taking the time to respond.

Regards,
Shannon

11/23/05 @ 14:20
Comment from: afshar [Member]

Dear All,

Here’s the link for the streaming video of my talk at the Perimeter Institute along with some related slides. It was a talk in the “PIQudos” seminar series.

http://streamer.perimeterinstitute.ca:81/mediasite/viewer/FrontEnd/Front.aspx?&shouldResize=False

Select “PIQudos” from the list on the left by scrolling down, and then click on
View: Measurement without “measurement”: Experimental violation of Complementarity and its aftermath

Abstract:
Bohr’s Principle of Complementarity of wave and particle aspects of quantum systems has been a cornerstone of quantum mechanics since its inception. Einstein, Schrodinger and deBroglie vehemently disagreed with Bohr for decades, but were unable to point out the error in Bohr’s arguments. I will report three recent experiments in which Complementarity fails, and argue that the results call for an upgrade of the Quantum Measurement theory. Finally, I will introduce the novel concept of Contextual Null Measurement (CNM) and discuss some of its surprising applications.
Web-page: users.rowan.edu/~afshar/
Preprint (published in Proc. SPIE 5866, 229-244, 2005): http://www.irims.org/quant-ph/030503/

It is important to bear in mind that this was an internal PI seminar with battle-hardened expert audience. So, please put the rare temper flares during the Q&A session in that context. It is common among physicists to get a bit more passionate when serious issues are being discussed. Nothing personal of course!

Regards.

P.S. Contents of the talk are copyright material and the source must be quoted. Preferably, you can wait until the unpublished material on CNM (currently under peer review) gets published.

12/01/05 @ 17:10
Comment from: quantum enforcer [Visitor]

Dear Prof Afshar

Thankyou for publishing this talk, it was excellent to see phyics people talking the talk for all to see. It seems that you still have some detractors out there but it seemed to go very well in the main.

thanks again

12/04/05 @ 09:05
Comment from: zekise [Visitor]

Greetings Prof. Afshar and Quantum Mirror - I am happy to see several new developments regarding the Afshar Complementarity experiment happen, ever since I was last here about a year ago (as “Unconscious Observer"). As my training is not in physics but rather computer science, I am not sure if the entanglement thought experiment proposed below will help shed any more light on this issue. Please view:

http://www.geocities.com/zekise/rochester-mandel.htm

I believe this faithfully reproduces the experiment conducted by Mandel at Rochester. C1 and C2 are spontaneous parametric down converters. A1 and B1 are entangled. So are A2 and B2. A1 and A2 are coherent. So are B1 and B2. (Pls. note the use of the term coherent here is slightly different from Afshar’s usage in the preprint.)

I understand that in this experiment Mandel observed no IP at D0 (a CCD array). Thus V = 0 and D1 or D2 provides us WWI, hence K = 1.

He then removed D1 and D2, and with the help of mirrors combined B1 and B2 together and decohered the combination so that WWI was lost. As a result, he observed an IP at D0, hence V = 1 and K = 0.

My question is, what happens if we instead move both D1 and D2 far off to a distance, so that the length of the B paths are much longer than the A paths. Will we see V = 1 restored while maintaining K = 1 (after a short delay) and thus produce a violation of PC?

If not, then what if we remove D1 and D2 altogether so that B1 and B2 never decohere, even though they are not combined? Will we get V = 1 (as K = 0)?

I wonder if such entanglement can be used to confirm the Afshar experiment? I would appreciate your opinion on this thought experiment.

01/03/06 @ 21:03
Comment from: Carl Looper [Visitor]

Hi Danko (if you’re out there)

To the extent that Afshar’s experiment is positioned as a violation of Copenhagen principle(s) we should provisionally set aside the math otherwise used to represent such principles. For example, the math that otherwise embodys Relativity Theory can’t be used to prove Newton incorrect anymore than the statement 2+2=4 can.

But through careful experiments, theoretical arguments, philosophical debates, a day in the art gallery, and the math, we can allow ourselves to adjust Newton’s equations to match those of Einstein’s. Otherwise we could just use Newton’s equations and say: see Einstein’s done the math wrong, he is therefore wrong.

Afshar’s experiment is a “which way” experiment. Such experiments already violate Copenhagen principles before they’ve even been performed. To follow Afshar’s experiment/argument is to (if only provisionally) employ a violation of the principle in preparing the experiment.

We should, against our better judgement, allow this.

The most famous “which way” experiment of all time is EPR. It begins as a violation of Bohr’s principle, before it is even performed. And it demonstrates (itself as) a violation.

Bohr’s comeback is to show how a correlation of the remote measurements, required to complete the demonstration, can not be performed without relocalising the remote measurements, ie. bringing them together. In the interim period, the information that would otherwise demonstrate the violation (through localisation) has yet to occur. The violation, in a sense, has yet to be demonstrated. It is in “waiting” so to speak.

Are we allowed to use this future event (localisation) to say what is taking place prior to such? Why not. We can just imagine ourselves in two places at once, performing the correlation, and thus predicting the conclusion which is otherwise demonstrated when done locally.

Bohr is in a good position here. He knows (to the extent that we can grant him such insight) that such a superpositioned observer can’t be localised any earlier than the measurements. The information otherwise held by our imaginary observer is as inaccessible (and therefore not information) as the remote measurements.

But insofar as we are allowed to imagine the violation, albeit retrospectively, we can imagine we’ve violated the Copenhagen principle.

And that is all that seems to matter in “which way” experiments.

But if a “which way” experiment could physically demonstrate a violation of Copenhagen principles, ie. before they could physically do so, only then would the principle be actually violated.

Obviously, if only by definition, this is impossible.

If, on the other hand, we read Bohr as advocating some limit on what we might imagine, or otherwise theorise as “there” prior to the demonstrated correlation, we could argue that Bohr is wrong.

We can, obviously, imagine anything.

But any serious analysis of Copenhagen (Bohr, Heisenberg, et al) would not see it as imposing any limits on our imagination per se. Afterall, the probability wave is an imaginary wave and forms the basis for predicting interference patterns.

‘Which way” measurements are at cross purposes to the principles of Copenhagen. Copenhagen is about what can, in fact, be measured. “Which way” measurements are about what could have been measured if it wasn’t for those pesky Copenhagen principles.

Carl Looper
21 January 2006.

01/20/06 @ 13:47
Comment from: Carl Looper [Visitor]

The $1000 challenge. The following either answers the challenge, or says the challenge can’t be answered. I leave that up to you. The wave function used to predict the interference patterns in each detector (or the probability of where a particle might be found in each detector) is computed across both detectors. This is consistent with conventional applications of quantum theory. The computed wave function defines an equal probability of finding a particle in one detector as it does the other. This probability is not affected by the introduction of the pinholes. The two waves emerging though the pinholes are the same wave function. Wavelets. That we can direct one wavelet to one detector, and the other wavelet, to the other detector, by means of the same lens (or different lenses) still doesn’t change this, or the probabilitys. Until the photon is measured, it still has an equal probability of being measured in one detector as it does the other. Again, this is consistent with conventional quantum theory. That we find a particle in one detector, and not the other, does not mean the wave (otherwise used to predict that particle’s location) came only through one pinhole. The same wave also went through the other pin hole, to the other detector. The same wave. Now the 50/50 probability of a particle being found in one detector vs the other is not defined by the wave per se, but the question - which detector? Each detector has been prepared with equal access to the same wave so the probability - in terms of the question - is 50/50. Carl Looper 21 January 2006 01/21/06 @ 00:32 Comment from: Carl Looper [Visitor]$1000 challenge - addendum

To the extent that the question in Afshar’s experiment is not “which detector” (future tense), but given a detection, “which pinhole” (past tense), one must perform an interpretation, insofar as such questions (in terms of QM) don’t make sense - literally.

The “particle” of which way questions, when translated into QM terms, could have been the probability of a particle, at the nominated junture (pinhole). But given the detection, this probability no longer exists. The probability of where the photon might be found or otherwise theorised - at an earlier time - would be everywhere zero, insofar as the photon detection is already given.

Since a which way question is asking something of the past, (rather than the future) we can construct a wave function from the downstream data, and propagate it backwards through the apparatus, in order to reconstruct what might be a suitable answer to a which way question.

To be consistent with the principles that saw each detection as the result of a wave distributed to both detectors, we must, therefore, use detections from both detectors to reconstruct the which way answer.

We will see (of course) that two pinholes are reconstructed - not one.

If we limit our downstream data to that produced in one detector our reconstruction will be, accordingly, just one pinhole. It is the choice of detector which determines which pin hole is reconstructed. Not the wave function. The wave function is constructed from data in both detectors.

The reconstruction of just one pin hole should tell us something is amiss. Where is the other pin hole?

It was edited out, insofar as the data that would have otherwise reconstructed it, was edited out.

Since the reconstruction of one pin hole, rather than two, is not based on the wave function but a decision regarding which data to use, the corresponding result does not constitute the identification of which way the wave/particle went. The result just tells us which detector was chosen to otherwise represent/imagine which way the wave/particle went.

Neo-classical reconstructivism.

Carl Looper
22 January 2006

01/21/06 @ 12:48
Comment from: Estimator [Visitor]

Dear Discussor!

I see the problem in any case should be addressed to detection of singnals from sorces. Could everyone in world measure with precise mathematical value which will not be changed by repetition of the further the same experiment for example what we call in optic significant physical characteristic is photocurrent. It s clear that we would like to say that some value has fluctuation and we should apply some approximation model.The argument is that we live in reality with there time developing natural laws. The detector will give us only some approximated by our model the answer on what happens with source.

Sincerely yours,
Estimator

02/10/06 @ 04:29
Comment from: Ian Cottrell [Visitor]

Dear Professor Afshar,

1. Your experiment contradicts a statement in Richard Feynman’s book “QED: The Strange Theory of Light and Matter”, page 81. Consequently the single particle experiments he refers to and any subsequent ones must have a flaw, which I presume is the issue of perturbation of the particle as it is measured passing through the aperture.

2. Has your experiment yet been carried out for particles with mass, as you have suggested should be done?

3. Presumably one of the crucial points to draw from the experimental results is that quantum measurement (or indeed the possibility of measurement) does not necessarily change/make reality, and consequently the concept of reality as existing separate to an observer, and without requiring one, can be restored?

Speculative questions:

4. Does the totality of experimental physical evidence indicate that quantum particle interference might never be related to having more than one particle (i.e. it is always single particle interference), or are there plenty of examples of definite multiple particle quantum interference?

5. I guess from your comments that you would disagree with the following statement:
The results of single particle self-interference experiments are -
• A single particle sent to a single aperture goes through as everybody would expect (with a single real trajectory seemingly randomly selected according to the appropriate single aperture wave function);
• A single particle sent to a double aperture also goes through one aperture only, but after exiting that aperture follows a modified single real trajectory (for some yet to be explained reason) but this time seemingly randomly selected from the two aperture wave function.
Why is the above wrong?

6. Coming back to perturbation during measurement. Is the only perturbation possible electron/photon interaction? Do you think that this then must/may reset the particle’s self-interfering capability? That is particle self-interference is only possible between interaction events and not across them.

02/13/06 @ 04:48
Comment from: zekise [Visitor]

Hi Ian - it appears to me that this forum has become dormant - Prof. Afshar is not responding to questions, and Quantum Mirror is no longer here (?). Let me try to answer your questions - I am also an amateur “non-formal” QM aficionado:

1) It would be helpful if you reproduce Fenyman’s statement on page 81.

2) I don’t believe Prof. Afshar has carried out his experiment with matter waves. The outcome should not be different.

3) I wholeheartedly agree with your assessment. A meme had befallen the physics community and some mystical followers for a few decades that, based on the Schroedinger Cat thought experiment, claimed that reality does not exist without “conscious” observers. That there is no planet on “51 Cygni” until somebody on earth 45 light years away discovers it, and then all of a sudden it gets formed. In the past 2 decades, the advent of Decoherence theory (Zeh, Zurek) has put to rest such irrational notions of self-centricity and solipsism.

It is not an observation or measurement that results in collapse. According to decoherence, as I understand it, it is simply an interaction that results in loss of coherence, which precipitates collapse. This usually is simply a photon hitting an object with many degrees of freedom. The issue is not whether there is an observer or not. The issue is whether the information “is there in principle” or not.

4) Multiple collimated photons do produce interference. Also for entanglement, you need multiple particles - however it can be argued that in full entanglement, the multiple particles are in reality a single particle. So yes, quantum phenomena do appear across multiple unrelated particles. Any (?) interaction between two (coherent) particles will produce a quantum phenomena.

5) I think you are pinpointing the central mystery to QM. If there is a second aperture open, the trajectory is affected by that, even though the trajectory does not go through the second aperture. If one insists in viewing this phenomena in particle and trajectory terms, indeed such mystery will arise. Under this interpretation, we have a paradox. That is why the wave interpretation of light has been proposed, and the wavefunction model can explain away this mystery (but produces another mystery, namely collapse and the interpretation of the wavefunction).

6) Perturbations are not limited to electrons and photons. Any system will do. What is important is the “degrees of freedom". An electron/photon interaction with the self-interfering object produces an entanglement that will kill the self-interference, through the production of the anti-fringe. So you raise a very good question.

Assume we have a matterwave interferometer. The massive molecule has passed a double slit and would produce an interference pattern if it hits the screen. But before it hits the screen, we shoot a photon at it that bounces off, and is now entangled with the molecule. So we will lose the self-interference (without correlation selection). We now break the entanglement by absorbing the photon by a system with large degrees of freedom.

Question is: would the self-interference pattern reappear, or is it irrevocably lost? I understand that Scully has shown that the self-interference is irrevocably lost (i.e. cannot be recovered without correlation selection). Therefore, there is no “reset” effect, and you are correct that self-interference will not preserve across an interaction.

I appreciate receiving feedback from Prof. Afshar and others.

Regards

02/20/06 @ 12:41
Comment from: afshar [Member]

Dear Friends,

Due to my lack of time to maintain this weblog, it will only be accessible as an archive until further notice. In the meantime, I can be reached through my e-mail afshar[at]rowan.edu.

Thank you for your cooperation and understanding.

Best regards.
Shahriar S. Afshar

03/01/06 @ 15:33