Talk:Afshar experiment/Archive 17

This is an archive of past discussions about Afshar experiment. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

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Archive 15

Um...

Quick question. It seems looking at the images often shown for the experiment that two interference patterns are shown, one on each detector. Is this true? If it is that is pretty confusing right there. Two interference patterns, one left and one right, building up a photon at a time... does that not viloate complementarity right there? Forget the wires. We can tell which hole every photon went through and yet see a clear interference pattern. Why are the wires needed at all? Dndn1011 20:34, 24 November 2006 (UTC)

The visual effect you are seeing in the detector image is not interference as such. The detector image is just an out of focus photograph of the wires backlit by an equally out of focus pinhole. You are seeing the out of focus shadows of the wires. Only the overall brightness of the image is actually used to infer interference. The inferred interference is occuring in the plane occupied by the wires. The wires either fail to absorb photons when both holes are open, or absorb photons when only one hole is open. The difference between these two situations results in a change in brightness at the detector. You can infer ("measure") interference accordingly. The principle of complementarity just says that either the wave function goes through both holes OR it goes through one hole. You can't say, in the same breath that it goes through both holes AND it goes through just one hole. Or you can say this but then you would sound confused if anyone was listening. --Carl A Looper 13:00, 25 November 2006 (UTC)

OK, that makes more sense.. the images I was refering to are misleading. Thanks for clarifying. Dndn1011 09:02, 27 November 2006 (UTC)

As Unruh says, the presence of the wires doesn't significantly change any empirical results, but it does alter how we should interpret complementarity (Proteus and all that). --Michael C. Price ^talk 23:11, 24 November 2006 (UTC)

As he says about his experiment. It does not explain however how we might end up with two images both having performed a measurement of interference (they show the interference pattern), and yet built up one photon at a time where it is measured which hole the photon passed through. OK I am a novice at complementarity, but if I find a way of measuring which hole the photon has passed through while still creating the interference pattern, have I not succeeded in measuring both? Actually the more I think of it the more I suspect that the concept of path is utterly meaningless. There are never paths of photons, just 'paths' of probabilities. Dndn1011 00:20, 25 November 2006 (UTC)

We return to the point I (and others) have made many times: no photon yields both which-path information and contributes to the interference pattern. Each photon that gets past the wires demonstrates wave properties as it passes the wires and particle particle properties as is passes the double slits and again later when it is focussed by the lenses, but no photon demonstrates both properties at the same time. Ergo absolutely no problem whatsoever in any way.--Michael C. Price ^talk 07:41, 25 November 2006 (UTC)

Sorry but this seems weak. No single photon can ever demonstrate wave properties when interfering with itself by this argument because the wave properties are derrived from sampling many cases over time. In other words if you examine a single photon you can never measure interference. If you examine many photons you still can't measure interefernce on a case by case basis. All you can do is observe the probabilities. But what you can do is observe that interference takes place even though which way information is retained. Complementarity by your argument is unsound because you can *never* measure measure the wave properties of a single photon whether you know which way the photon went or not. Dndn1011 09:14, 25 November 2006 (UTC)

You seem to have missed my point which is that no photon demonstrates both pure wave and particle properties at the same time. (Highlighted relevant text in previous message.) Afshar's experiment demonstrates wave and particle properties at the same time for different photons, but not at the same time for any individual photon. --Michael C. Price ^talk 09:57, 25 November 2006 (UTC)

No I understand that point. And my point is that is never possible, ever, to measure the wave properties of a single photon. Dndn1011 11:06, 25 November 2006 (UTC)

Bounce a plane-wave incident photon off a mirror and measure the mirror's recoil momentum p. The perpendicular wavelength of the recoiled photon given by de Broglie:

\lambda =h/p

. The photon reflects off the entire surface of the mirror. Or measure the colour of a photon (a measure of its energy E), and

\lambda =hc/E

. --Michael C. Price ^talk 11:22, 25 November 2006 (UTC)

Or... measure the deflection of a photon because of refraction. Yes, yes. However it is only an assumption that because these effects can be mathematically represented as wave functions, they are the result of wave behavior. Just because they behave like a wave it does not mean that they are a wave. Those examples you give do not involve unpredictability on a photon by photon basis. Also the path information is fully known so you might be arguing a point of view that breaks complementarity. I was, however, refering to the interference effect. You can not measure the interference probabilities (the probability of a photon hiting an particular area of the target in the original double slit experiment) from look at a single photon, no more than you can measure the probability of a coin toss from a single toss. Dndn1011 11:48, 25 November 2006 (UTC)

The path information in the mirror example is not known. As I said, the photon bounces off the entire mirror, i.e. is delocalised across its entire surface. So no violation of complementarity. --Michael C. Price ^talk 11:58, 25 November 2006 (UTC)

What if the photons hit the mirror in a tight beam? Anyway, that's enough from me for now, I have enough to work through for a while without raising more questions. But thanks for the time you have spent answering my questions it is appreciated. Dndn1011 09:06, 27 November 2006 (UTC)

If they hit in a tight beam their momentum would not be precise, by Heisenberg's uncertainty principle. --Michael C. Price ^talk 10:27, 27 November 2006 (UTC)

Dear Dndn1011, I have explained perfectly what you ask on interference and complementarity, in Wikipedia - Georgiev's 4 slit experiment. The slits are made distinguishable 1,2 vs. 3,4. However since 1,2 are not distinguishable between themselves they form a double slit interference pattern - self-interference. But this pattern does not cross-interfere with the waves coming from slits 3,4! If all four slits are indistinguishable, then the observed picture will not be 2 x double-slit interference pattern but a single 4-slit interference! Now you ask where comes the interference for each pinhole. See single pinhole diffraction - it is self-interference of light rays coming from different parts of the same pinhole. The single slit interference cannot violate complementarity because you don't claim that you know from which part of the pinhole the light comes. This is NOT cross-interference with light from the opposite pinhole. In order to see the single slit diffraction pattern - called Airy disc pattern, the diameter of the slit should be larger than the wavelength of the photon. If you somehow make distinguishable the different parts of the pinhole, the Airy pattern of the circular pinhole will be ruined. This is what complementarity says. So one big conclusion: interference is always there, the complementarity is about not-interference of waves which are distinguishable vs interference of waves wich are not-distinguishable. Regards, Danko Georgiev MD 07:50, 25 November 2006 (UTC)

Thanks for new information (new to my frame of reference, heh), I will take a look at it. Dndn1011 09:18, 25 November 2006 (UTC)

Hi Dndn1011. I think we need to revisit the general point in the ongoing debate section of the main article. Where it says the Afshar experiment exposes assumptions. This is meant to mean assumptions about the principle of complementarity - not assumptions by the principle of complementarity. Although it could be that as well. The mathematical axioms are themselves assumptions but they correctly embody the principle (as far as they go). But the principle itself is not immune to other assumptions - those which might incorrectly embody the principle. The afshar experiment can be understood as exposing both kinds of assumptions. We should understand by the term "Afshar" that this does not mean the person. The term "Afshar" merely identifys the experiment in question. The experiment exposes assumptions - assumptions that anyone can make, including Afshar the person, about the principle of complementarity - assumptions that Bohr himself might make in a first reading of the experiment. This is probably more of a philosophical/historical research topic than a math/physics topic. --Carl A Looper 00:53, 26 November 2006 (UTC)

As for the text in the article, please just makes whatever changes you see fit. I merely attempted to clarify the text. Ultimately, it is clear that it is hard to decipher this topic. My motivation primarily has been to try and help the formulation of an article that can be understood by general readers, and this means I would need to understand it too. I have to say that after a lot of discussion it is still not clear to me what this is all about. There are arguments presented that clearly make no sense (i.e. Unruh's experiment really does have nothing to do with Ashfar's). The nature of complementatiry seems to shift according to the needs of the person presenting an argument. At the end of this debate, I am no closer to really understanding the principles of what is going on and the article is still poor. But is has been an interesting ride.Dndn1011

To me Unruh's experiment looks highly relevant, as I suspect it would to most people with technical familiarity with the subject, provided they read all of Unruh's explanation (it is it a subtle argument).--Michael C. Price ^talk 11:29, 28 November 2006 (UTC)

As a simple example, I read the principle of complementarity as being born within the context of experimental observations. That is the assumption I make. But it can equally be understood as finding birth within a purely rational framework. And that is the assumption a rationalist will make. They are, strangely, compatible with each other. But you have to decide which philosophical framework you are going to use. A strictly emperical one or a strictly rational one. You can't have it both ways. The principle of complementarity will hunt you down. --Carl A Looper 01:30, 26 November 2006 (UTC)

You seem to be suggesting that theory and practice are incomplatible. That the rational appraoch is not compatible with the experimental. If this is the case here, I would argue this as indicating broken science. The only real interpretation I have of Afhsar's experiement right now is that in order to leave complementarity intact it is necessary to push the principle to the point where it actually is no longer useful. It is similar in effect to presenting an argument that the universe is an observer created reality, and ask to prove this wrong. It cannot be proven wrong experimentally and philosphical debate would also be fruitless (It has been debated for over 2000 years I believe). Dndn1011 09:55, 27 November 2006 (UTC)

At the risk of inflaming unnecessary debate, a purely rationalist framework is unable to say anything about the collapse of the wave function. Rationally then, one just abolishes such. Decoherence theory is working along such lines. String theory is doing something similar. Meanwhile, on the other side of the philosophical divide, empericists don't need to account for the collapse of the wave function. They are working with the construction of physical observables, not theoretical ones - not to prove or disprove any theoretical understanding of such but for it's own sake. There is a pleasure to be gained from looking at a physically realised interference pattern. An experimental physicist is somebody who goes to the local shop, buys a cheap laser pointer and a small mirror. He goes home and scratches fine groves into the emulsion on the back of what is otherwise the plain glass of the mirror. He then sends the laser light through the back of the mirror, ie. through the slits he has scratched, and onto the wall of his livingroom. He sits back and experiences the interference pattern. This experience is physically igniting connections in his brain. Now this experience can be 'simulated' by just reading a mathematical equation or a book on the mysterys of quantum theory. But it will be a qualitatively different "experience", one no less worth pursuing, just one that is different. --Carl A Looper 02:11, 26 November 2006 (UTC)

I kind of see what you are getting at. But has not the mission of science been to marry the two together? Dndn1011 09:55, 27 November 2006 (UTC)

Now the recombination of these two, theory on the one side and practice on the other, is not the proper domain of either. But it is still something that is done. And it is still science. The question is how. Personally I don't think the Afshar experiment really helps. It sits in a blindspot. A more rigourous approach is to work either side of the blindspot, first one way and then another. It won't necessarily change the blindspot but it does help. Attempts to violate complementarity throw one into a very high level domain of philosophy, theory and history. And one should be prepared for that. If your brain is at the point of a breakdown, take a break. Visit the art gallery. Take a walk in the park. Have a look at the world. The world speaks. Take notes. Think. --Carl A Looper 03:55, 26 November 2006 (UTC)

:) Thanks, I like that, made me smile. Afhsar's experiment does appear to me to expose a blind spot, but will not directly helps us other that perhaps being a giant arrow saying "Look at this". But I would also say that any theory or philosophical view which can not be succinctly described is probably wrong. The ultimate answers to wave/particle duality, unification of relativity and quantum mechanics and all that stuff will be simple, I think. We just have problems seeing it because, well... perhaps we can only directly experience the observable universe and the mechanism which underlies this is outside that which we are to observe. We can make theories about that which we cannot see of course. But occasionally aspects of the mechanism of the universe get exposed, and then we have to change the theory. Or we can just say "Who cares", and enjoy the ride. Maybe that is the ultimate wisdom ;) Dndn1011 09:56, 27 November 2006 (UTC)

Hi dndn1011. The principle of complementarity is actually very simple but it has broad scope which means it can be used in many places. Basically the word "complementary" can be replaced with the words "mutually exclusive". The principle of mutual exclusivity we might say. In information theory it is embodied in what is called the "XOR" operator. It should not be confused with the "OR" operator. The "OR" operator fails to make a distinction between A AND B being true, and A OR B being true. If this distinction is important, as it is in quantum theory, then one should use the XOR operator instead. Hope this is succinct. --Carl A Looper 21:20, 27 November 2006 (UTC)

Oh I am very familiar with XOR, being a programmer, who cut his teeth writing in machine code (without even an assembler). I believe understand what complementarity is, or was derrived from quite well. In the original twin slit experient, you can only observe the interference pattern if both holes are open. Both holes open means you can't know which way the photon went. If you close a hole you can know, but the interference pattern is lost. Since there is no way of measuring the photon's path "in flight" so to speak (without modifying the result), this results in this mutual exclusivity. However you don't need to have this rather uncomfortable logical hack if you remove the assumption that photons travel at all. In other words, if the measurement of "which way" has no meaning, neither does complementarity. What seems complicated to me is all the complex reasoning required to keep complementarity alive. Why bother? It is far easier to start from the viewpoint that in fact photons do not really travel at all. Perhaps they are always a wave in fact. How can a particle be also a wave? By making use of additional dimensions this should be possible... and of course additional dimensions are hard to measire or even think of. Finally, if complementatiry is meant to solve the logical problem of wave-particle duality by effectively saying that there is no need to consider both at the same time, we still end up with interesting questions like.... how does a photon acting as a particle have a frequency component? One particle, one wavelength. At the same time. As someone who really does not know what they are talking about, I am tempted to say... that the wave is a fluctuation of some 4th dimension in space. There could also be an extra dimension in time, to explain other strange things like how linked events can resolve correctly and instantaneously over large distances apparently breaking the barrier to information travel faster than the speed of light. I believe there is some multi-dimensional theory with 10 or 11 dimensions or something. Then there is string theory and countless other things (including, what was it, Transactional Theory?)... are these not all ways of getting rid of the need to artificially speperate wave and particle behaviours? But enough from me, I am out of my depth. Dndn1011 00:32, 28 November 2006 (UTC)

"Which way" is a red herring. There is it's classical meaning, ie. a particle tracing out a line through space over time. And it's modern quantum mechanical meaning which imposes a limit on the classical meaning rather than completely erasing it. I tend to completely forgo "which way" models altogther. But they remain as a way of explaining the wave function collapse problem, ie. if we imagine the photon is always a particle then we would always detect it as such. The wave function is like some sort of weird state it is in when not measured. But equally weird is imagining the particle travelling space. We only want it to be a particle because it is detected as one. The quantum. But the quantum is only ever detected at a single point in space, and even more importantly, a single point in time. It is a four dimensional point. Or n-dimensional point. It has no existence anywhere else or anywhen else. The wave function, on the other hand, has the opposite problem. It has no existence within a single point. Waves can only exist over space and over time. The wave/particle descriptions constitute mutually exclusive descriptions of a single thing which we otherwise call the quantum, or a "particle", or a wave packet, or a wavicle, or an xoracle (just made that up). Part of the problem is the way in which we read an interference pattern. It is composed of all these point like detections. And we think of the point like detections as being more real than their distribution. Due to our classical inheritance. But their distribution is just as real. It is just that we've inherited a mindset in which pictures (the interference pattern is a picture) is treated like some sort of optical illusion. Some sort of special effect. A mirage. The detections are treated as if they were of more substance. But it's not as bad today as it was a hundred years ago. Yet we still privalage the model over the image. The model is the reality or cause. The image is the illusion or effect. I see them as equal but opposite versions of each other. The principle of complementarity again. But I work more on the image side. The empericist side. So I'm more like the experimental physicist than the mathematicain, and so prone to "interpretational delusions" as a rationalist might say. But I can see it just as clearly the other way. No problem at all. And I wholeheartedly recommend rationalism. It is a very clear and precise language. And it has cleared up many problems I've had to deal with. But not all. The reason is that I work in the visual arts. --Carl A Looper 07:54, 28 November 2006 (UTC)

The XOR operator (or principle of complementarity) provides the bizzare reunification of waves and particles, and every other duality one can think of. It's quite perfect. Using XOR one can transfer information from A to B without it ever existing at any point in spacetime between A and B.

Here is an example, which is how teleportation works:

Let Q be a perfectly random number.

Compose information (M) at location A.

Using XOR, create a new message(K): K = M XOR Q

Now the new message K is a random number. No matter how much you analyse K you will not find any information in it.

Take K to location B.

Recreate the message at location B by reapplying the XOR operator: M = K XOR Q.

How did the message get from A to B?

Both K and Q are completely random numbers.

--Carl A Looper 02:24, 28 November 2006 (UTC)

I might just add that the AND operator, which you are entertaining as the alternative, doen't work. And the OR operator will only work three out of four times. You'll get 1/4 noise in your reconstructed message. But the XOR operator works all the time. That's the only reason to use it. Because it works. --Carl A Looper 02:42, 28 November 2006 (UTC)

The principle of complementarity, once understood, can't be violated. It would be like saying you have found the XOR operator, that you have used in some machine code, has magically produced some result other than the one that XOR normally does. But this is the wrong conclusion. One should not assume the XOR operator has failed. One must hunt down the source of the bug and find what has really caused the result. You will probably discover that you have accidently used the OR operator instead. If you don't debug the code you will just have to conclude your computer code has somehow demonstrated a violation of complementarity. Which you are free to do. I used to always argue with my vintage Commodore64 when it said SYNTAX ERROR. I was convinced the computer was not reading my code properly :) --Carl A Looper 03:55, 28 November 2006 (UTC)

I give up

After all this discussion, the article is going backwards. Once again we have OR and opinion and it really does not measure up to the facts. All discussion has been overwritten once again by the opinions of Mr. Price, with complete disregard to contrary views. Perhaps We should call this article "Mr. Price's Research on Afhsar's Experiment".
Once again the really weak argument that effcetively states "Since QM supports Complementarity, nothing can possibly in the whole wide universe ever violate it because the entire universe is made up of QM, and there is if any evidence appears to the contrary go fry an egg".
Then if this is no enough, we have "Afshar's experiment does not yield which which way information and demonstrate interference effects for any individual particle (the photon), any more than the classic double slit experiment does.". This is completely untrue. As I spelled out above, it is shown that photons that could only have avoided the wires because of interference still register on a targetn revealing which way information. This is the point that makes the Afshar experiment not at all like the classic experiement. The statement by Mr. Price is highly misleading to the relevance of the expriment and the basis of the claims it makes.
Since Mr. Price is not going away I have aminded the article as appropriate. I hope you like the changes. Good bye Dndn1011 16:56, 28 November 2006 (UTC)

Hi Dndn1011, I'm surprised at your strong negative response. I regard you as an honest inquirer. Your statement "All discussion has been overwritten once again by the opinions of Mr. Price, with complete disregard to contrary views." is not correct: I have not overwritten anything, I merely restored text that had been deleted by Carl A Looper and added an extra comment, both of which are well sourced. I left the previous comments about complementarity untouched, even though they were rather meandering, un-Wiki-stylistic and content-free, IMO.

Your parody of my text shows a misunderstanding of the relation between complementarity, the formalism and empiricism. Afshar does not claim to overturn the formalism (that would require unexpected empirical input which no one claims); so just accept that and focus on the relationship between the formalism and complementarity. This has been explained previously. Your reservations or misunderstandings do not seem to be shared by Bohr, Unruh, Motl et al.

Your specific criticism of my sentence "Afshar's experiment does not yield which which way information and demonstrate interference effects for any individual particle (the photon), any more than the classic double slit experiment does." is incorrect, although I accept that it is hard to demonstrate that to someone who lacks a sound grounding in quantum physics. I'll try again later.

--Michael C. Price ^talk 21:01, 28 November 2006 (UTC)

Hi dndn1011. Can I say you did a great job thinking through the debate. Don't worry about M Price. He's a petulant child who likes to throw the book at people. But he mistakes the last letter of his surname for a 'k'. One day that will occur to him and he'll wake in fright. You are right to question what you read and you should think through it. That is what understanding is all about. And only by allowing various sides of an argument some sway can that occur. Also, you saw an interference pattern in the detector data. Well, from an information theory point of view, that is exactly what you are seeing. That data, when run back through a fourier transform and a specification of the experiment, minus any assumptions about the pinhole plane, will reconstruct two pinholes - not one. And that's data from only one detector. One of the pinholes will be very faint, but it will be there. But where did it come from? It comes from the fact that the wires placed in the experiment leave a trace in the data. The wires constitute a memory of the previous experiment in which an actual interference pattern was recorded (or from just the postulation of such, as in a computer simulation). I didn't think of that until you mentioned the "interference effect". If you had not questioned that effect it might have gone unnoticed or dismissed as irrelevant by our man with a mission, mister michael whatshisname. --Carl A Looper 19:03, 28 November 2006 (UTC)

And Afshar is right to question the principle of complementarity for exactly the same reason. The name of the game is understanding, not who is right and who is wrong. People like MP should make an effort to understand that. QM is not the end of the story. Is is just the start. It has given birth to an understanding of the physical world as information. The book is not closed. It has just been opened and there are plenty of blank pages there. --Carl A Looper 20:03, 28 November 2006 (UTC)

MP strikes again

"Niels Bohr stated "an adequate tool for a complementary way of description is offered precisely by the quantum-mechanical formalism" [6] In this view, since the photons in the experiment obey the precise mathematical laws of quantum mechanics (the formalism), Bohr's complementarity principle can't be violated by the experiment." - Michael Price

Niels Bohr stated ". . . we are presented with a choice of either tracing the path of the particle, or observing interference effects . . ."[15]. Afshar's experiment does not yield which which way information and demonstrate interference effects for any individual particle (the photon), any more than the classic double slit or Wheeler's delayed choice experiment does. The claim of complementarity violation in Afshar's experiment is based on a statistical argument and applies to large numbers of photons only, not to any single photon (cf "the particle" in Bohr's statement)" - Michael Price

Why does MP persist? Leaving aside "which way", how pray tell, would one demonstrate interference using a single photon anyway? It's a complete mismanagement of Drezet's argument.

Drezet's argument is that a demonstration of interference requires one to do so statistically, ie. by a build up of individual events. One can not demonstrate interference using a single photon, or just a few of them. That's the whole point of Drezet's argument. But to read MP's argument is to read it as if Afshar shouln't be using a statistical argument.

But he should.

Or at least that is Drezet's argument - that Afshar should be using a statistical demonstration of interference.

An adequate word for describing Michael Price is offered precisely by the words "consistently confused". In this view, since Michael Price obeys such a description, the words "consistently confused" can not be violated by Michael Price.

--Carl A Looper 07:58, 29 November 2006 (UTC)

Note: Afshar does in fact use a statistical demonstration of interference. Drezet's argument is somewhat more involved.--Carl A Looper 08:32, 29 November 2006 (UTC)

The absence of comment on Bohr's first quote indicates acceptance? --Michael C. Price

Why should the absence of comment indicate anything at all?

:-) :-) --Michael C. Price ^talk 09:12, 30 November 2006 (UTC)

But I will comment on the second quote. It's a very good quote. Quite obviously Bohr - as reconstructed from the quote - is wrong. The Afshar experiment demonstrates that the either/or choice is not the only choice. We CAN observe interference AND trace the path of a particle in the same experiment at the same time. Bohr obviously entertained the thought that one could, ex principle, do such a thing, but that the complementary principle physically prevented us from doing so. As it turns out the principle is only a theoretical impediment. It is like the collapse of the wave function. It is only a theoretical impediment that prevents the wave function collapsing. In practice it happens. The universe doesn't care. And on that simple level (which is the best level to begin) the Afshar experiment can be said to demonstrate a violation of Bohr's "principle". --Carl A Looper 07:18, 30 November 2006 (UTC)

I see: Bohr is wrong. You should write that up and publish it. Anyway this is irrelevant: you admit that the quote is a good one and that's all that matters for Wikipedia. --Michael C. Price ^talk 09:12, 30 November 2006 (UTC)

Many people already have. For all intents and purposes the Bohr we read in the historical record, through snippets and quotes, is a Bohr as new to quantum theory as anyone today would be. Ask yourself, why does he need to qualify waves and particles in terms of physical experiments anyway? They are mathematically complementary in the first place. But he's working in an age when such things, in a physical context, seemed incomprehensible. They did not have textbooks to look up and tell them how to understand such. His principle emerges within a language unsuited to it. But as far as I'm concerned he's right on the money. Yet language is precisely the domain in which his principle will subsist. What he says rather than what he doesn't say is what the principle will become. There are, in effect, two Bohrs that emerge. One who understands complementarity - the one we have turned into a quantum figurehead, and one who didn't quite understand it himself. But how do we disentangle these two? When we turn to Bohr's principle, as distinct from it's subsequent formulations, we must take the good with the bad. And the bad is that what "Bohr" has said can be understood as misleading or just wrong. Why talk about complementarity in terms of the "same experiment" or the "same time" at all? it's just wrong. But he did and so Bohr's principle of complementarity is one entangled in the historical context of the day. And violations of that "principle" are entirely understandable. --Carl A Looper 11:08, 30 November 2006 (UTC)

Regarding Bohr's 2nd comment, which is combined with Drezet's, Drezet concludes:

"To conclude, in spite of Afshar's claim we still need two experiments in order to exploit the totality of the phenomenon. As pointed out originally by Bohr, we can not use information associated with a same photon event to rebuild in a statistical way (i.e. by an accumulation of such events) the two complementary distributions of photons in the image plane and in the interference plane. The hypothesis of Afshar that we only need some partial information concerning the interference pattern in order to reconstruct the complete interference is only based on the idea that the fringes already exist. The whole reasoning is circular and for this reason misleading."

i.e. Drezet's argument is that Afshar's argument is a statistical one and that it fails to demonstrate complementarity violation. And that Bohr maintains that such a statistical approach is flawed in that it will not yield data to support complementarity violation. --Michael C. Price ^talk 09:45, 29 November 2006 (UTC)

I'm not going to elaborate on Drezet's argument. I understand it and I'm sure you do too. But you are irrelevant here. I am irrelevant here. What is important is whether what is written works. The way it reads is that Afshar's use of a statistical approach invalidates his attempt at a violation (as indeed one could argue) but implying that he should have measured interference some other way, ie. non-statistically. Which is not the right idea to leave in the air like that. It doesn't actually matter if you are a quantum logical genius who understands the correct meaning. What matters is if someone other than yourself can get the drift. What matters are the actual words you write and the meanings those words generate. It's an art of sorts.

In collaboration with DnDn1011 we put together something that would not alientate quantum logical geniuses such as yourself AND not alienate the general reader as well. My first attempt was way off the mark. And I'm grateful that DnDn1011 stepped in and had a go. It struck the right note. The experiment, and it's critiques, need to be accessible so that people can make up their own minds. Despite what you might think people other than yourself can actually think for themselves. But if you think they've got it wrong then by all means write a paper. That's what papers are for. The main article is not the right place for two sentence pseudo-critiques. And if two sentence are all you are actually capable of doing then put those two sentences in a paper. And I'll put a link to it. Really. I will. --Carl A Looper 08:19, 30 November 2006 (UTC)

Again you misunderstand Wikipedia. It is the place for sourced critiques, and that is what I have provided, not a load of vague philosophical OR waffle (which in deference to your views I have not deleted). --Michael C. Price ^talk 09:12, 30 November 2006 (UTC)

The critiques are already sourced in the list of links. Your parasitic reformulations are worse than irrelevant. They are viral. I have not dared to touch them out of fear of infection. --Carl A Looper 11:08, 30 November 2006 (UTC)

I shall not sink to your level and delete your text from the article. --Michael C. Price ^talk 13:40, 30 November 2006 (UTC)

Oh how honorable. That's Price-less coming from someone who won't engage in debates, just does what he likes, and appoints himself the Head of the Inquisition into quantum heretics. No hominems to add here. He just adds himself. --Carl A Looper 19:31, 30 November 2006 (UTC)

What's the point of engaging with someone who uses rude words and name calling as a substitute for reasoned debate? If you wish to be taken seriously then start acting in a more mature fashion. --Michael C. Price ^talk 21:49, 30 November 2006 (UTC)

Well, at last. It dawns on MP the reason for reason. --Carl A Looper 21:59, 30 November 2006 (UTC)

What a load of baloney Michael! You’ve given yourself free reign to write whatever OR you wish, knowing all too well that I cannot correct the article. That is a shameless abuse of Wiki rules. You also blatantly ignore other editors when they point out your OR nonsense. Any expert knows that contrary to your claim above, Complementarity IS of a statistical nature itself. So let me explain this for you: the two properties addressed by PC are interference and which way information. It is relatively easy to show that which-way information is a single particle property, however, it is IMPOSSIBLE to discern an interference pattern for a single photon. You need large numbers of photons to verify that the individual photons within the pattern behaved as waves, i.e. interference pattern is an ensemble property (READ MY PAPER it’s all in there.) Bohr's MISTAKE was using two different types of properties which-way information that is a single-particle property, and interference pattern that is a multi particle or ensemble property on the same footing essentially comparing apples and oranges. Also, contrary to your claim the which-way information in my experiment is highly reliable (K~99%), and this is accepted by a number of experts in Ivy schools and other institutions. Finally the claim that the complmentary observable are not verified for the same photon in my experiment is absolutely false. Every SINGLE photon that lands in either image (thus providing the which-way information) must have avoided the wires in order to make it to the image. I prove in my paper that the only way that can happen in QM is accepting the presence of interference. Interference can only be established (like any other experiment) by running a large number of photons to produce a reliable interference pattern at the wires. You MUST correct the misinformation you are putting on the article, otherwise be man enough to assign your name to these OR so that other physicists understand the "depths" of your understanding of this topic. P.S. Bohr was WRONG in assuming that the QM formalism supported his philosophical view embodied in QM formalism, it does not. Apart from experimental embodiments that enforce PC through HUP or entanglement, there is nothing in the formalism itself that prohibits presence of interference and which-way information in the same experiment. The Schrodinger equation when applied to the experiment and the wavefunction unitarily evolved in time, preserves which way information and in the region of overlap, produces interference. What Bohr said was MEASURING the both aspects for the same photon was impossible. Well, when you apply non-perturbative techniques like I have, you verify the Schrodinger equation while demonstrating Bohr's "principle" was wrong; period. -- Prof. Afshar 14:54, 29 November 2006 (UTC)

Your "measurement" of the interference effects of a single photon as it passes by the wires is by inference only. I could just as well claim that a photon propagating through a single slit experiment demonstrates pure particle properties as it passes through the single slit (K=1) and demonstrates inferred pure wave properties later (V=1) since we know that it propagates according to a wave-equation the rest of the time. Imagine an internal set of double slits if need be. So why is it that this experiment is not seen as violating complementarity? --Michael C. Price ^talk 15:33, 29 November 2006 (UTC)

From your question above, it is absolutely clear to me that you have a lot of reading to catch up with my friend! I sincerely wish you really spent some time to read my paper and the references therein. On page 3 of my SPIE paper (http://www.irims.org/quant-ph/030503/) I address exactly the issue that you've raised above:"It is noteworthy to mention that quantum mechanics does not forbid the presence of non-complementary wave and particle behaviours in the same experimental setup. What is forbidden is the presence of sharp complementary wave and particle behaviours in the same experiment. Such complementary observables are those whose projection operators do not commute [20]." Ref. [20]: G. Kar, A. Roy, S. Ghosh and D. Sarkar, Los Alamos National Laboratory e-print(xxx.lanl.gov), quant-ph/9901026; S. Bandyopadhyay, Phys. Lett. A 276 (2000) 233. When there is only one slit open, the self-interference of the beam emerging from that slit does not constitute a complementary observable to the which-way information, and is thus not subject to Complementarity. Let me know if you have any questions on this issue, which is admittedly a bit difficult to grasp, especially for someone who is not versed in the literature involved. I expect you to change the text of the article to reflect the above fact. Regards.-- Prof. Afshar 08:09, 30 November 2006 (UTC)

Instead of ad hominems how about actually answering the question I asked? --Michael C. Price ^talk 09:12, 30 November 2006 (UTC)

Can you read English? I answered your "question" above. You asked "So why is it that this experiment is not seen as violating complementarity?" My answer was the projection operators for the passage of the photon from a single slit and the subsequent diffraction pattern to which it belongs commute and thus are NOT COMPLEMENTARY, because one IMPLIES the other, not CONTRIDICT it. Thus they which-way information and the diffraction pattern in your “experiment” are not relevant to studying Complementarity. I gave you the ref. for this established fact. If you continue ignoring facts I'm afraid you are nothing but a stubborn and ignorant fool. Remember, although you cower from associating your name to the OR you spew on the main article page, however, people are reading this talk page, and I will make sure my colleaugues take into consideration the kind of ignorant statements you are making. If you care about your reputation, you should withdraw your OR immediately. -- Prof. Afshar 15:41, 30 November 2006 (UTC)

So which is zero in the single slit experiment, V or K? --Michael C. Price ^talk 21:46, 30 November 2006 (UTC)

This question is actually pretty easy to answer, and I hope the following would help you understand what Complementarity in which-way experiments actually means. The answer to your question is: K=0, V=1. I know you are probably surprised that I said K=0, after all there is only one slit from which the photon could have originated, so the K must have been 1! However, the situation is a great deal more subtle; so, let me explain to you why here K=0. (Take a deep breath now!...Steady... here we go) Contrary to the common belief by non-specialists, in a double-slit welcher-weg experiment, the "which-way information" is actually the "which-slit" information (this fact is well-known among experts, if in doubt, just ask Unruh). Complementarity says if you know which one of the TWO slits the photon originated from, then the wavefunctions from those TWO slits cannot interfere to produce an interference pattern. If you can somehow show that a photon originated from ONE of the TWO slit, AND yet see evidence of interference by these TWO wavefunctions, THEN you violate the PC, as shown in my experiment. In contrast, in the single slit case you mentioned, the which-way information pertains not to "through which slit", but rather to from what part of the single slit the photon had originated. That is because the interference pattern in this case is the single slit diffraction pattern, produced by the interference of the wavefunction(s) coming from various points on the edge of the slit. There is, however, a way to make the single slit experiment you mentioned, equivalent to mine: place a lens at a suitable distance from the single slit and image it to its imaging plane, (this way you can tell which photon came from which part of the slit), and at the same time place a circular loop of wire in the first minimum of the Airy disk (equivalent to the central dark fringes of the two-slit welcher weg). This loop of wire essentially performs the non-perturbative measurement of the interference of the wavefucntions from various locations on the edges of the single slit, and the image gives us the which-way information. Now this modified single slit experiment is a true wlecher weg experiment in which Complementarity can be tested. I hope this is clear enough. Please let me know if you any question in this regard. P.S. Please take the time to calmly read through my reply at least one more time, it is not as trivial as you might suspect.-- Prof. Afshar 06:26, 1 December 2006 (UTC)

Truely incredible, we have a one slit experiment and you've managed to convince yourself that K=0. I'm speechless. But inserting the wires is not a "non-perturbative measurement", it's a "non-measurement". No photon that is focussed by the lens is measured by the wire. Your statement about measuring the interference pattern is one of inference only and irrelevant, as I've already said: since we know that it propagates according to a wave-equation the rest of the time. --Michael C. Price ^talk 06:44, 1 December 2006 (UTC)

I'm glad you think it is incredible. You can ask any expert in the field whether what I have said above is correct or not. Why don't you start with Lucien Hardy, or Unruh, or Wheler himself. How about Greenberger, or Khrennikov? Just make sure you provide them with the exact quotation from my response above, not your own impression of it. As for the inference issue, that is true, although if the wires were detectors with QE=1 (which is possible in principle) they would have provided direct measurement of destructive interference (dark fringes.) However, one does not have to prove the presence of interference to rule out PC; as long as you can show that a decoherent distribution (one without any fringes), predicted by PC, was not present at the wires, you violate it. You might wish to read Dicke's paper on null measurements in QM: R.H. Dicke, “Interaction-free quantum measurements: A paradox?,” Am J. Phys. 49(10), 925 (1981). A fantastic read in itself, which is... well, simply incredible :) -- Prof. Afshar 07:16, 1 December 2006 (UTC)

What is truely incredible is that you list Unruh as one of experts that agrees with you. :-) :-) --Michael C. Price ^talk 07:33, 1 December 2006 (UTC)

Well, he agrees with the which-way information part at least. He seems to have a good grasp of what Complemenatry observables are. BTW/I have absolutely no doubt Prof. Bandyopadhyay will agree with all of my analysis above.-- Prof. Afshar 07:42, 1 December 2006 (UTC)

Which shows that the which-way argument is irrelevant since Unruh does not agree with your conclusions. BTW I am already familiar with interaction-free measurements; if that's what you claim your wires are then call them that: "non-pertubative" is not a good description since people will think that you're refering to QFT non-pertubative analysis. The point is still irrelevant since interaction free measurements are used to extract information not confirm what we already know, namely that the photon propagates according to a wave-equation. Finally I have no doubt that you have no doubt that Prof. Bandyopadhyay will agree with everything you say. That something you seem to share with Danko -- an absence of self-critical faculties -- in addition to an addiction to exclamation marks. --Michael C. Price ^talk 08:08, 1 December 2006 (UTC)

No it is highly relevant, as YOUR problem happens to be with my definition of which-way information and that K=0 above. Since you respect Unruh, I thought his opinion on the issue may be of interest to you. As for self-criticism, suffice it to say that I scrutinzed every aspect of my results by consulting world-class experts for 3 full years before I announced the experiment at Harvard. And, yes, I have never been good with punctuation marks, but do not believe using faces ;-) are good alternatives either!!! What? Does that annoy you?!!!!-- Prof. Afshar 08:27, 1 December 2006 (UTC)

Your stylistic point has merit, I must confess, and is quite amusing, but what of the substantive point you have ignored, viz that "interaction free measurements are used to extract information not confirm what we already know, namely that the photon propagates according to a wave-equation." Your wires (in idealised form) do not perform a measurement, interaction free or not, since they yield no information. This is the core flaw of the Afshar's experiment; the idealised wires do not perform a measurement. --Michael C. Price ^talk 08:40, 1 December 2006 (UTC)

The wave function is itself an inference. We do not know it is there anymore than Shrodinger does. We postulate it as there. The experiment can be understood as a demonstration of the postulate. But we can also read the experiment as one requiring a postulate. Why do the photons not hit the wires when both holes are open? We just do what Shrodinger does. Postulate a wave function. Or perhaps Shrodinger just looked up his own equation in a textbook to explain it. --Carl A Looper 23:18, 1 December 2006 (UTC)

The point is not about inference, but about information and measurement. A measurement, by definition, yields information. The idealised wires yield no information; they are not performing measurements (with both slits open). --Michael C. Price ^talk 00:20, 2 December 2006 (UTC)

MP's relentless McCarthyesque mode of inquiry is astonishing. It's as if the world actually owes him some sort of explanation. And if it's not forthcoming then anything he says or thinks, to fill the hole, must be right. --Carl A Looper 23:19, 30 November 2006 (UTC)

People often say, when visiting an art gallery, "What's so good about that. I could have done that". Well, true, they could have, but they didn't. --Carl A Looper 07:18, 30 November 2006 (UTC)