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Concerning the Afshar experiment

There is one year already the physicist S. Afshar (see preprint) working at Harvard university realized a very controversial experiment in order to refute the famous principle of Niels Bohr called complementarity. This experiment was described in an article of the British journal New scientist [(2457, 24 juillet 2004)]. It was clear for me since the beginning that the result was badly interpreted and that the reasoning of Afshar was misleading.

In order to refute the claim of Afshar I would like, here, to explain briefly my reasoning.

File:Drezet.png

Principle of Afshar's experiment.

The optical experiment represented on the figure included is essentially an extension of a ‘gedanken’ experiment proposed by Wheeler and called the delayed choice experiment. A coherent light impinges on a screen containing two slits or apertures A and B. Light diffracts and produce interference fringes at large distance from the apertures. As well known we can use a lens L to observe these fringes in the focal plane (F). Alternatively we can decide to observe the image A' and B' of the holes in the image plane (I). This is simple and is only a problem of classical optics.

However difficulties arise if we consider the same problem with photon. Indeed a photon is a discrete entity which can produce a local click on a detector. If we suppose that light is made of particle how to explain the existence of the interference? This is the canonical problem called wave particle duality. Einstein and others, like de Broglie or Bohm, tried to justify this curiosity of nature but Bohr found a simple solution to this problem which is to dismiss the entire issue by avoiding any reference to objective reality. For Bohr and Heisenberg it is a complete non sense to search an explanation for such quantum behaviour. Indeed such explanation(s) could not be experimentally tested.

Bohr realized that effectively if you build up a model attributing a trajectory to photons then you should be able to observe experimentally these trajectories. If you can't do that your model is without any physical interest. However Bohr remarked that the observation of the path of the photon always disturbs the coherence of the wave and erase the interferences. In the present context we have the choice between detecting a photon in the image plane or in the focal plane. This means that we have the choice between using each photon to build up the images A' and B' ('which path' information) or the interferogram. But since a photon can not be absorbed twice we can not make the two observations with the same particle. This is the reason why Bohr called this property complementarity.

Now let go to the Afshar modification of the preceding experiment. Afshar decided to observe his photons in the image plane (I). Nevertheless he introduced in the focal plane a periodical grid of absorbing wires (in fact he worked just in front of the lens but this doesn't affect my reasoning). The wires are located at the exact minimum of the fringes. Naturally the experiment is not affected by this introduction because the intensity on the wires is close to zero producing consequently no additional disturbances or diffractions on the light propagation. The two spots in A' and B' are then unchanged.

However since no photon are absorbed this give us information on the intensity at the wires location. We know then that the probability for a photon to cross the section of the wire is null and this is already something. Afshar believes that this information is sufficient to prove the existence of fringes in the plane. He is wrong. Naturally he is however right saying that clearly the intensity can not be uniform in the focal plane. But he can not really say what the shape of the fringes in this plane is. Bohr’s principle speaks about physical observation not about metaphysical expectation. To define experimentally the fringes he should use other photons that the ones recorded in the image plane. If you need an analogy you can imagine the following situation. You are living in Paris and you can see from your beautiful flat (with a rent of 8000 $ per month) the apex of the Eiffel tower. Can you deduce from that the shape of the Eiffel tower? Obviously not... in the Afshar experiment every thing is the same.

This is clearly in disagreement with the conclusion of Afshar and is sufficient to refute all his reasoning.

--Drezet (30 may 2005)

I take issue with the term "metaphysical expectation" surely it should be plain old "a priori knowledge". In effect, Afshar needs to show that:

a) setting a measurement device using a-priori knowledge of the "wave function" together with..

b) a priori knowledge of the effect of the device on the wave-function [plain old Maxwell for photons] given that setting of the equipment (wires)

is the same thing as making an "observation" as Bohr intended.

A simple case in point is the polarization analyzer. If I align an analyzer with a polarized source, then make a subsequent analysis of polarization with a second downstream analyzer then the first "measurement" will not affect the results. If I do not have a-priori knowledge, then the results are meaningless, because the measurent will be determined by the first polarizer.

In Afshar's setup, moving the wires through a range of spacings [or shifting wavelength] would cause a periodic dimming and brightening of the images. That way, one could "measure" the interference pattern. Leaving the wires at a spacing where the images are at maximum brightness adds no information. Similarly, you can only measure the linear polarization state of a source by observing the effect of rotating the analyzer [or source], leaving both fixed - tell you almost nothing.

The nature of the Afshar's wires and the polarizer are the same, they are logical "denials" [like describing the weather by saying "it is not snowing"] - if a photon emerges from an analyzer, all one can say is; That its incident state was not exactly aligned at 90deg to that analyzer. Similarly, the wires say that the particle is "not here". If the wires dim an image, then they are not exactly placed at the nulls in the pattern. This is very different fom Bohr who spoke of specifically determining a particle's position before the interference pattern is observed.

All Afshar's experiment shows is that a single "denial" measurment is not an "observation". The statistical effect of a denial apparatus on all possible states needs to be measured before the result be considered an observation.

--Murphy (24 Dec 2005)

Remarks concerning Unruh's reasoning

In august 2004 the well known physicist Unruh (see [1]) proposed a simple counter argument (i.e. a gedanken experiment) in order to reveal the mistake in the reasoning of S. Afshar. The gedanken experiment of Unruh uses a Mach-Zehnder version of the original set up build by Afshar and seems to be in appearance an elegant alternative to the experiment described in [2]. However in spite of its interest it can be finally observed that the reasoning of Unruh missed the essential point of the argumentation. In order to prove that we will analyse briefly Unruh's proposal.

The experiment starts with the splitting of a initial photon wave packet into two by a half silvered mirror. The two wave packet 1 and 2 are then redirected on a second beam splitter and separated into the beams 3 and 4. Finally using two mirrors and a last beam splitter we obtain the two beams 5 and 6 (corresponding to the two spots A' and B' in Afshar's set up). Unruh observed correctly that his set up is for the essential equivalent to the one build by Afshar. He remarked in particular that if no absorbing device is introduced in the interferometer then the photon will never follow the path 4. This is clearly equivalent to the existence of fringes in front of Afshar's lens. After crossing the last beam splitter the photon has a probability of 50% to be detected in 5 or 6. However, and this is fundamental, nobody can tell us with this set up from which path 1 or 2 comes the photon detected in 5 or 6. We can be tempted to close one of the two paths 1 or 2 in order to see effectively the path followed by the photon. If we do that we always record the photon in 5 if 2 is blocked and in 6 if 1 is blocked. Additionally the photon has the same probability to be in the arm 3 an 4 which means no interference. This is clearly the equivalent of the single slit experiment (i.e. a single path experiment).

Nevertheless by closing one of the two paths we have different physical situations. It is indeed evident that we can not reproduce the interference observed in 4 and 3 simply by adding the results observed in the two single path experiments. This is the reason why in the double path experiment of Unruh nobody can tell from which path 1 or 2 comes a photon detected in 5 or 6. It is then not true to tell that the photon observed in 5 (respectively 6) has a probability of 100% of coming from 1 (respectively 2) since nobody can test this fact experimentally without strongly disturbing the system. The same conclusion is valid with the lens. We observed two spots A' and B' but we don’t know if the photon detected comes from A or B: This is a metaphysical question for a quantum physicist. What we can deduce from the observation in 5 and 6 or in A' and B' is the number of photons coming from 1 and 2 but this is only a statistical result which should not be confused with the concept of which path information.

Now Unruh add a beam block in the arm 4. In the double path experiment this changes nothing because no waves propagate in this arm. This is clearly the same conclusion that the one obtained with the wires in the focal plane of the lens. However in the single path experiments the results are different since the beam going through 4 is blocked: the photon has now an equal chance to be recorded in 5 or 6. Unruh deduced from that that in the double path set up a photon detected in 5 or 6 has a probability of 50% of coming from 1 or 2. He then concludes that the experiment of Afshar doesn't conserve which path path information. However as analyzed previously the concept of which path information is dangerous and fallacious in quantum mechanics. Indeed by adding again the statistical prediction of the the two single path experiments (i.e. by adding the number of particle observed )we can not create the 'fringes' present in 3 and 4. It is then wrong to tell that in the double path experiment with absorber in 4 the photon detected in 5 or 6 has an equal chance to come from 1 and 2. In reality nobody knows it and nobody can really test such assumption without changing dramatically the experimental situations.

It can be added that the experiment of Afshar differs from the one proposed by Unruh on one point: if we introduce the wires in the single slit experiment the probability for the photon to be scattered or absorbed is only of few percents. This is far from the 50% of Unruh and this proves again that the essential point is not the hypothetical dualism between which path and interference but the complementarity between the observation in the focal plane and the image plane (Afshar's experiment). It can be observed finally that in Unruh's double paths experiment with absorber in 4 we can simultaneously measure the number of photon in 5 an 6 and be sure that no photon goes through the arm 4 (in the other case the absorber should count some photons). On this point the conclusion is different regarding Unruh's or Afshar's experiment since we explained previously that in the Afshar experiment the complete knowlege of the fringes and of the images can not be obtained with the same particles. The present discussion is not however in contradiction with our analysis of Afshar's experiment. Indeed in the experiment of Afshar the numbers of photons in the focal and image plane are associated with two non commutative observable (momentum and position) which are consequently complementary. It is then forbidden to build up simultaneously (i.e. by using the same particles) the two statistics in the two planes. But such constraint doesn't exist in the experiment of Unruh since the observation in 5 and 6 are not complementary of the observation in 4 and 3. Unruh's experiment is then not a test of complementarity and can not be compared to the experiment of Afshar.

Since I respect the scientific work of Bill Unruh I Hope that he will not consider my argumentation like an agression (PS: I agree with him that the argument of Danko Georgiev is a non-argument : with the same kind of non-argument it will be soon possible to prove that Mickey mouse is a cat and that Schrödinger is Mickey mouse. )

I would like to add that I made at the beginning (july 2004) the same mistake that Unruh did. My argument was the following : With the wires present we observe that the signal in A' with only A open is modeified when we open both A and B . This prove that something coming from B is going in A'. and then this should erase the which path . But in reality the changment is only of few percents and of 50 %. This prove that I was wrong (like Unruh). Now my argumentation is different as described before.

--Drezet (30 May 2005 few seconds later)

Remarks concerning remark concerning Unruh's reasoning

OK - please note that Wikipedia's ambitions have to be limited, to providing a good survey, in any scientific controversy. We cannot here try to establish truths, or make arguments, that are in advance of quite well-established scientific literature, i.e. the published papers (or at least easily accessible pre-publications, of good reputation). This is not a forum for cutting-edge physics; the standards of survey articles are the appropriate ones. Charles Matthews 15:40, 30 May 2005 (UTC)

reply: since the work of Afshar didn't respect the rules mentioned by you here I dont see why you object me to do the same. My reaction is natural: I'm a professional physicist and I always submit my work to reviewed journal. Since the work of afshar doesnt obviously respect the good order: 1) review article 2) popular article and web forum I decided to react against Afshar's way of acting. Naturally if his work will be published (perhaps in Mickey mouse journal) I will comment officially. regards --Drezet (30 May 2005 one minute later)

Wikipedia policy on 'original research' is quite strict. And we certainly never accept arguments of the type 'if X breaks your policy, so can I'. Never. Charles Matthews 16:07, 30 May 2005 (UTC)

Also please see my comments above. There are several problems with this point counterpoint approach in Wikipedia which are clearly illustrated by this article.

• The "referees" (in this case, you, Motl, Unruh and others) are immediately subject to a critique by the author submitting the work. This allows the author an unusual advantage in the review process. Imagine submitting a paper to a journal where it can never get rejected, but in which reviewers comment's are always subject to public review by the author. Now journals do allow for further review of an editorial ruling, sometimes, but this review process terminates.

• This particular author has used legal threats against one "reviewer" (Motl). These legal threats were completely unrelated to utterly childish behavior on th epart of Motl, and in any case are against WP policy.

• I have tried to edit the article using only widely known facts about Afshar, his experiment, the formal statement of the principle of complementarity using consistent histories and the onlinecritiques. I have not concluded anything other than (1) his work has not been published in a peer-reviewed journal (2) His work is regarded with skepticism.

• The final leap of reasoning that the formal statement using consistent histories does not appear to be proven, is not my problem or anybody else's problem on WP at least and I refuse to be put in the position of having to prove Afshar is wrong. The burden is on him to get his paper peer-reviewed. --CSTAR 16:35, 30 May 2005 (UTC)

Dear CSTAR and Charles Matthews, Thank you for your comments . Since you are probably the most adult persons on this page I can only say that I feel guilty to play the same game that Afshar. But this is the risk on this free web page (the philosophy of a Blog is very dangerous by definition since effectivellly there is no reviewer). I Will not include anymore comments concerning Afshar's work but you should try to understand my reaction: Imagine you are a physicist interested in quantum mechanics like me. You try to solve all quantum paradox just in order to clarify your thought. Due to the fact that you are like me very pretentious you are totally convinced that Bohr is not the end of physics and that Einstein will be back (no like the christ i hope).

After that one morning you drink a good coffee made with pure colombian powder... and now you open new scientist july 24 2004 you see the title of Afshar article and then you have suddenly 2 reactions: 1) you laugh like crazy and 2) you become furious because this work is in certain cense published and that this is non sense and go against any basic idea od objectivity and science.

what should you do if like me you believe that science is and must be a place for logic and rationality?

Ok now I am still waiting for any review of Afshar's work even if a realize that this is less probable that to find one day that the moon is made of green cheese.

Finally there is a problem with reviewed article: sometime there are wrong because the reviewer was mistaken and some other physicist will publish some replies later. The process is more objectif that here but the difference is only quantitative not qualitative . So dont be furious if i included my comment to Afshar's work here. If you dont like my way of thinking /acting supress my comment but then eliminate the page of Afshar too.

with best regards and no agressivity

Aurelien Drezet ,Graz --Drezet (30 May 2005 few minutes and one coffee later)

Few scientists have not had to deal with the unpleasant experience of journal rejection (maybe with the exception of Witten). The outcome in that case is rewrite and resubmit or ask for independent advice or perhaps desist and submit to the arXiv and leave it at that.--CSTAR 17:52, 30 May 2005 (UTC)

You are completely right (even if I am not sure that even Witten was never rejected: But I am sure That Isaac Newton was not rejected) and I dont understand why the work of Afshar is not on the arxiv (los Alamos). Perhaps he should ask some body to rewrite his paper with him (I say that not for the english of Afshar which is better than mine but ffor the very non usual style) and to submit it to an other journal less important (a paper is a paper after all : if you can add it to your CV it is good for you). I still don't understand why he submitted his work to PRL (why not to Nature or the Times? like Einstein). Since the article is very controversial he should submit it to something like foundation of physics. But OK this is not my problem (who I am after all to give advices of that kind?) since I believe (honestly I should say: I know ) that Afshar's work is scientifically unbelievable.

stay in peace and keep cool --Drezet

Interference of crossed beams !!!

Dear Aurelien,

WHY YOU ARE SO BLIND? Take A CAREFUL LOOK OF YOU PICTURE THAT SHOWS HOW THE IMAGE IS PRODUCED - THERE IS CROSSING OF THE BEAMS THAT PRODUCE THE IMAGES A' AND B'. [Since the angle theta is close to zero the mixing of the two channels can be considered complete, see the formula below, in Afshar's setup the distance to lens is 4.2 m, while the distance between the pinholes is JUST 2 mm i.e. theta -> zero]. If you really are "physicist" as you call yourself then you should KNOW that:

"Cross term of crossed beams is proportinal to 2 cos(kx.sin_theta) where 2 x theta is the angle between the crossed beams". In Afshar's experiment the production of the image is result of crossed beams, so there IS INTERFERENCE even IF there is no GRID before the lens.

Please just take a look of the lecture of Rick Trebino:

Rick Trebino (2003) Lecture 18. Coherence and Interference

http://www.physics.gatech.edu/gcuo/UltrafastOptics/3803/OpticsI18CoherenceInterference.ppt

In order to see who is Rick Trebino check:

http://www.physics.gatech.edu/people/faculty/rtrebino.html

And it seems that you need to read a full course in optics:

http://www.physics.gatech.edu/gcuo/UltrafastOptics/index.html

Best,

dear Danko just one word to express my feeling HAHAHAHAHAHOUHOUHOUHI!!!!! ARG arg it is so good to laugh

Your are very comical but as usual you are 1) nervous and 2) wrong. I am no blind (but probably i will become blind soon if I continue to read such comments) and clearly you are not physicist (but you are however comical as I told you before). Perhaps I was too fast for you and I regreat it. I am unfortunatelly for you a specialist of optics so your no-comments are really inapropriate. I see that you know what is a fringe ...great: I am happy for you . But this is not sufficient to understand quantum mechanics and complementarity.So now you shoud do the second step after the re-discovery of interference you should rediscover the photon.

alea jacta est

--Drezet

Dear Drezet,

first of all your commentary is ridiculous. You call yourself "specialist in optics", but I don't feel you understand the basics of optics. This is evident even from your picture of Afshar's experiment.

• First of all the grid is before the lens, and not after the lens. IF the grid is after the lens there will be great loss of photons because the interference fringes that exist before the lens, hardly will preswerve their size and shape after the converging action of the lens.
• Second, your picture is wrong because the distance from the double slit to the lens is 4.2 m and from the lens to the image plane the distance is 1.38 m. The proportions are clearly exactly the opposite of your drawing. [Not to speak that the distance between the two slits is just 0.002 m, so the angle theta is approaching zero].
• Third, simply you don't understand the meaning of the term interference, you don't have any deep understanding of the mathematical formalism of complementarity, so you cannot understand the predictive power of the usage of density matrices. Certainly the existence of Fourier transform between the lens focal planes is indicator for interference because without interference you CANNOT have Fourier transform.
• And last but not least, your 'laughing' suggests me that I should not even mention your name in my paper [because you are not scientist whose name deserves to be quoted at all!], and I will present your ideas as 'third person's possible opinion' and I will then make my coment on such wrong views.

Surely the readers of Wikipedia can do their own reading and decide whose ideas are right. The truth does not care about our human desires, and always survives the critique. So far noone has presented clear mathematical reply to my thesis, that is presented in un-ambiguous mathematical way.

p.s. I did not understood your laugh that concerns interference and fringes. My point was to OBVIOUSLY point out, that you cannot avoid INTEFFERENCE of crossed light beams, or CROSSED photon trajectories. Therefore you are the one who does not understand the quantum nature of the photon. :-)))

Best,

Danko Georgiev, MD

I'm a little puzzled by your reference to "Fourier transform"; particularly something like

Certainly the existence of Fourier transform between the lens focal planes is indicator for interference because without interference you CANNOT have Fourier transform.

Do you mean something like high-frequency asymptotics (as formalized by Fourier integral operators)? I fear I am joining the ranks of the blind here. --CSTAR 17:30, 31 May 2005 (UTC)

HAhaha HIHI HOUHOU BETTER AND BETTER!! Dear Danko it will be really a pleasure for me if you can remove my name from your paper. Really it will be even better for my dignity of physicist and human to never see my name associated with yours. I have nothing against you but the discussion become senseless and if we continue like that we will become impolite.

Just a point a lens is definitivelly a good system to image and it is then a good sytem to realize one experiment like the delayed choice experiment of Wheeler. If you dont agree with me then you disagree with Wheeler and I guess with the the rest of the universe.

PS: Dear CSTAR let me help you for understanding the thought of Danko: I think that he tells us without fourier transform we have not fourier transform HAHAHAHA HIHI ARG ARG (life is fantastic) --Drezet

Dear CSTAR,

Your question is good one, because you seek for the link between the interference and Fourier transform. Well, the Fourier transform [let's denote it f(x) --> F(x)] transforms a function from time into frequency domain. This means that every point from one of the functions say f(x) is projected with some weight upon every point of F(x). Actually there is no one-to-one mapping between element of f(x) and element F(x), but there is holographic transform. Actually the Fourier transform is one of the basic things that you learn when you study the principles of holography. Steven Lehar (2003). An Intuitive Explanation of Fourier Theory http://cns-alumni.bu.edu/~slehar/fourier/fourier.html

But of course it is better if you read my paper [3] and how Fourier optics is linked to lens action. Also I provide example WHEN if there is no interference, the lens does not perform Fourier transform between its focal planes. All my results are backed up with detailed mathematics.

What about Drezet's laugh - it shows incompetence : I do not come to the tautology without fourier transform we have not fourier transform - Actually IF you don't have interference, you CANNOT implement Fourier transform, but the inverse is NOT TRUE - IF you don't implement Fourier transform, this does not mean that you cannot have interference. So, dear Drezet, you are on the wrong way again. You cannot even provide some clever joke, and you have scored auto-goal again :-)

Best,

Danko

Suppose you cut some interval of f(x) [say from -1 to +3]. What you will obtain is NOT F(x) with some cut in it, but you will get again F(x) varying from -oo to +oo, without gap in it. You may read this paper on holography

Well of course, this is just the fact that multiplication gets turned into convolution by Fourier transformation. --CSTAR 20:34, 31 May 2005 (UTC)

Dear Danko after such explanation I can only correct my thought: Danko wanted in fact to say without interference there is no interference OUAH HAHA HIGGI HOOUUHOUHOU ARG ARG kauf kauf!! Ok now i stop joking with you. You was like Afshar a good entertainment but my job is to work on quantum and nano optics not to discuss about how many angels can sit on the point of a needle --Drezet

dear Danko , I realized that I could offend you (for this I apologize even if your not very polite too).

I can not give you an anwer for your questions since you missed to many important points (optics, quantum optics ,logic....). Then I have presently no other choice that to stop this senseless discussion with you.

I regreat that we discussed on this page with such agressive style and I apologize too to the creator of this interesting philosophical forum.

I forgot to say that I realized that you are not a professional physicist . This is not a problem for me and I was stupid to offend you since I am a professional physicist and I learned with time how to find a mistakein a reasonnig very quickly. You seem to be an autodidact and this is very courageous.

But like me you should learn how to be prudent and modest (perhaps I have more to do in this direction).

your argumentation copncerning Afshar is not good but I have no time to explain you again and again why. If you want we can discuss with private email ?

with best regards Aurelien Drezet

dr Aurelien Drezet, institut for experimental physik Graz Austria.

--Drezet

Interference of crossed beams (bis repetita)

I want to add a short scientific comment concerning Afshar's work :

Afshar not only claimed that he can circumvent Bohr’s complementarity but that he can effectively determine the path followed by the particle. Afshar, following here a assumption originally enounced by Bohr , Heisenberg and Wheeler, accepted that even with the two pinholes open a photon trajectory (if trajectory there is) will necessarily connect a pinhole to its optical image as it is if the other pinhole would be closed. However, as is was realized by numerous physicists as de Broglie, Bohm, Bell and Scully, this is a free metaphysical assumption which depends of our model of reality and which can not in general be experimentally tested [read for example “ Surrealistic Bohm trajectories”, Englert et al in Z. Naturforsch. Vol 47a , p 1175.].

Effectively nothing in the Afshar’s experiment forbids a photon coming from one pinhole to go in the ‘wrong’ detector for the second pinhole (this is the case for example in the Bohm’s theory). Looking the image of a pinhole recorded in a statistical way by a myriad of photon will not say us from which pinhole an individual photon come from but just how many photons crossed this pinhole (in reality it is even more terrible since quantum mechanics only tell us what will happen if we observe the photon). In counterpart of course we can not see the fringes and the complementarity principle of Bohr will be, as in every quantum experiment, naturally respected.

Since I am not a defender of Bohm' view I will not go further in this direction but you see that th concept of trajectory is ambiguous for a photon. --Drezet

Dear Aurelien,

I am glad that you start to see what I am saying - there is no which way information in the two pinhole case. The fact that there is lens changes nothing. If all those people including Wheeler et al. have ever claimed that the lens image contains the which way info at the image plane, then i will have to add them in the black list of the people who had done severe error.

By the way - as I know, Wheeler determines the which way with 2 telescopes = 2 lenses, not a single lens, and the 2 lenses do not cross the light beams. Do you see the difference?

Well, by for now, I will be back soon. Contact me by e-mail for further discussion.

Best,

Danko Georgiev, MD

Dear Danko just to tell you that I desagree Afshar's experiment is unlike the Schrodinger cat completely dead and it is useless to try a reanimation : you are not Frankenstein --Drezet

I noticed the "neutrality disputed" tag on the main Afshar page and wondered if I should remove my entry, "Kastner's Interpretation", on that page. If it is desired that I do this, please let me know, and I'll be happy to do so. May I still list a reference to my paper somewhere on the main Afshar page?

Thanks, R. Kastner

The POV banner has nothing to do with your entry. I put the POV banner up about a month ago, but the page now seems a little more balanced (although still could use some trimming in the pro/con section). Whatever happens to that section, my guess is that your reference (as well as Motl's and Unruh's) should probably remain, but of course, this being Wikipedia, who knows?--CSTAR 23:33, 17 Jun 2005 (UTC)

Dear Dr. Kastner, I have no qualms about moving your entry, as well as my response to it, to this discussion page until we work out our differnces through e-mail and my weblog. But since I have been accused of being biased in the past, I cannot do it. Perhaps you and CSTAR could sort that out? Best regards.--Prof. Afshar 11:41, 18 Jun 2005 (UTC)

Proposed deletion

There's too much of XYZ's objections and Afshar responses. I think they should be deleted and replaced with references to blogs and other websites. However, I also think it is fair to add the statement the preponderance of scientific opinion is that Afshar's experiment does not refute complementarity. I don't like use of "opinion" here but I can't think of a better word that would conform to NPOV policy. --CSTAR 16:45, 21 Jun 2005 (UTC)

I'd certainly support that. As it is, the article is more personal-bloggish than encyclopedic. -- Reuben 18:38, 21 Jun 2005 (UTC)

I support that with 100 % and even if iam sad that my proper last comment will desapear (sob! sob!) I think that the mention :the preponderance of scientific opinion is that Afshar's experiment does not refute complementarity is extremely good (even if I dont know personally any physicist which is pro-Afshar ). --Drezet

I recently gave a talk at a physics conference in Vaxjo University in Sweden, where the majority (30+ physicists) agreed with my conclusion that the common reading of Bohr's Complementarity principle (based on the current literature) is ruled out. Some initial objections were replaced by acceptance of my conclusion upon further discussion after the talk. So I certainly disagree with the sentence the preponderance of scientific opinion is that Afshar's experiment does not refute complementarity. That is the opinion of a few vociferous opponents, not the scientific community. Also, the paper has been accepted for publication in Proc. SPIE 5866, 229-244 (July 2005): http://bookstore.spie.org/index.cfm?fuseaction=DetailVolume&productid=604724 . This and other publications in the works, as well as the growing list of supporters of the work (see my earlier entries for a partial list) reflect the fact that although my experiment/conclusion is controversial, it is aptly viewed by the major practitioners of the field as a revealing and relevant one vis-a-vis the discourse on the foundations of QM. As mentioned before, any claims regarding "the preponderance of scientific opinion" without a scientific polling of the experts in the field would be baseless and irresponsible. At this point the majority seem to be agnostic rather than antagonistic. I suggest all those who have made their opposition publicly available to attend my talk at the upcoming SPIE meeting in San Diego, where I would have the opportunity to address their comments in person. Simply put, the fat lady has not song yet despite the opinions of some. Nonetheless, replacing the long Contoversy section with web links is a good idea. You may also wish to include the Proc. SPIE ref. for the paper which also includes further suggested experiments.--Afshar 01:11, 22 Jun 2005 (UTC)

Reply to Afshar: You will note that I have tried to keep my personal opinion regarding your interpretation of the experiment out of this discussion. I have tried to base my edits and comments clearly on what others have stated. However, I think your claim that this is the opinion of a few vociferous opponents is a bit disingenuous. Moreover I was the one that made the comment earlier in this discussion that

A few words in the introduction bother me, particularly "many physicists" are skeptical which I believe should be "most physicists" are skeptical. However, I have not conducted a scientific poll, and I am sure that fact would be brought to my attention.

Indeed, you just did bring it to my attention as I expected. However, I do not regard this as you do as being baseless and irresponsible. Your evidence in support of this last assertion is purely anecdotal. In any case I suggest that we wait for more comments from other interested parties on this page. --CSTAR 20:55, 21 Jun 2005 (UTC)

Reply of a vociferous oponent : Oups CSTAR was faster than me!! I would like nevertheless to vociferate a bit:

I read the list of works in the conference: This is full of vociferous oponents of QM . When we put together many people believing that the moon is made of green cheese they will rarely desagree on their favorite axiom... In other terms the list does not represent a fair-sample of the physic comunauty(This looks as if I was speaking about loopholes in Bell's experiment Hi hihi). NB: there is however a good point for afshar. Indeed a real paper exists (OK!! a Proceeding). So now this is a litle bit more serious in the sense that any one can use a reference to comment the work of Afshar.

Actual deletion

I like the new page : this is much more neutral and objectif. NB: I changed the part concerning complementarity (using a part of an article I am currently writing ) if somebody disagree we can discuss. --Drezet 22 june

Dear Drezet,

your entry concerning complementarity is ridiculous. You speak about metaphysics, so possibly you are "good metaphysicist" not good physicist. Physics uses strict mathematics and you use words that can be interpreted as one wants.

I have added the mathematical formulation of complementarity and I also write and develop my paper on complementarity. The text in my entry is from a lecture of Bob Eisenstein, professor in physics. I will add in my paper how the different calculations of probability (i) add then square, or (ii) square then add produce "interference" or "clumping" patterns.

I am curious to know why you don't like mathematics? And also I don't understand your way of doing science - my advice is read Popper for the "demarcation criterion".

Best,

Danko

Danko. Complementrity does have a mathematical definition in terms of consistent histories. See p 170 of Omnes book or read some of Griffiths' papers.--CSTAR 20:33, 22 Jun 2005 (UTC)

I have read several identical formulations presented in many textbooks and lectures, and I have presented them very clearly. What says Omnes I don't know, but it doesn't matter. Bob Eisentein's formulation is strict and clear. I have done my work to clearly link the terms "which way" and "no which way" to classical computational gates - AND and XOR. Because in "which way" you may actually have no real knowledge but just XOR [describing mixed state] and in "no which way" you actually know a lot - you certainly know XNOR, and one more logical step leads you to AND gate. This is resembling Many World Interpretation of QM, but it just says "superposition is real". Reality of superposition is also suggested in TI, and in Penrose's OR. So this is how the QM is, and this is not my own invention.

Danko