Local realism ruled out? (was: Photon entanglement and )

[JesseM]

Ah, I read through the many exchanges you had with "colorspace" and I will only end up echoing his many complaints. We don't need to repeat that :-)

Many of colorspace's complaints seemed to suggest little working understanding of how real theories of physics work, like his argument in post #12 that if it would take time for a computer to compute which copies of signals from Bob should be matched to which copies of Alice, then it must take time in reality too (when of course we have plenty of examples of theories which say the state of each point in space is being continuously updated in response to its surroundings according to differential equations, in a way that would be impossible to simulate perfectly accurately with finite computing power...likewise the fact that an infinite number of Feynman diagrams must be summed to get completely accurate predictions about probabilities in quantum field theory doesn't imply that nature takes an infinite time to 'compute' the outgoing particles in a collision). That's why I eventually abandoned the discussion, since I can't really explain the mathematically abstract nature of modern physics to someone who's insistent on acting incredulous towards any theory that doesn't make sense in concrete "common sense" terms. Since you seem more well-versed in modern physics than colorspace, a discussion of what you find implausible about this type of model might be more fruitful, if you have the time and are so inclined (if not, no problem).

 

[DrChinese]

I would use DrC's semantic choice here and refuse to say GR is wrong :-)

Sorry bout giving things an accidental semantic twist. When it comes to theories, I have a decidedly utilitarian bent. But some theories *are* useless enough to be called wrong.

But of course, GR is not one of those. I will defend Einstein as I do Newton.

RUTA, your research sounds very exciting! Always enjoy your posts.

 

[DevilsAvocado]

my hero was Einstein

Einstein is my hero!

As an aside, we're working on just such a theory now -- nonseparable Regge calculus.

Cool! (And you know me and English... first I’d read "Reggae calculus"... ())

Since our Relational Blockworld interpretation of QM and QFT assumes a nonseparable theory X underlying quantum physics*, we developed a "direct action," path integral approach over graphs for theory X. Regge calculus is a path integral approach over graphs for GR so, of course, that's where we expect to link theory X to classical physics.

Very cool and interesting! My personal "layman-gut-feeling" tell me that this kind of approach must be the only logical path forward, looking for the underlying "theory X". I cannot understand how some people seems to be willing to do almost anything to "disarm" the EPR-Bell issue, including getting hazardous close to deceitfulness, in order to get back to status quo and business as usual.

I think EPR & Bell's Theorem is gift from above! How utterly boring it would be, if everything was already worked out... no scientific news... no interesting discussions on internet... what should one do? Retire and play golf!? :zzz:

To me, the current situation looks like 1887 and http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment" , when the experimental data was crying out for a 'logical' solution!

As I understand, this new underlying "theory X" must be fairly compatible with both QM & SR/GR, as this has been the case in history of science. Crackpots, starting from square one by dismissing both QM & SR/GR, are most probably doomed to lose...

But how to marry QM + GR is way beyond my understanding. But it is nevertheless very thrilling!

(Let me know when "it’s" solved! )

 

[DevilsAvocado]

As I mentioned at the end of post #581, there is a theoretical loophole in Bell's proof due to the implicit assumption that each measurement yields a unique outcome, so with a many-worlds-type interpretation you could have a local model consistent with observed violations of Bell inequalities in experiments with all the experimental loopholes closed:

Thanks for the info JesseM. I am aware that MWI is a possible solution to get out of the EPR(B) paradox. I’ll check out your toy model, and The Everett FAQ. I think I have a question about EPR & MWI...

Meanwhile, what’s your view on EPR/MWI and splitting worlds, in respect of Occam's razor...?

 

[JesseM]

Meanwhile, what’s your view on EPR/MWI and splitting worlds, in respect of Occam's razor...?

Personally I lean strongly towards MWI type interpretations, I think Occam's razor just says our theoretical assumptions should be fairly simple but it doesn't say that the actual number of entities predicted by the theory should be small (for example, it's no strike against current cosmological theories that they postulate a huge number of stars in the observable universe, and likely many more--perhaps an infinite number--beyond the limits of what we can observe).

 

[RUTA]

Many of colorspace's complaints seemed to suggest little working understanding of how real theories of physics work, like his argument in post #12 that if it would take time for a computer to compute which copies of signals from Bob should be matched to which copies of Alice, then it must take time in reality too (when of course we have plenty of examples of theories which say the state of each point in space is being continuously updated in response to its surroundings according to differential equations, in a way that would be impossible to simulate perfectly accurately with finite computing power...likewise the fact that an infinite number of Feynman diagrams must be summed to get completely accurate predictions about probabilities in quantum field theory doesn't imply that nature takes an infinite time to 'compute' the outgoing particles in a collision). That's why I eventually abandoned the discussion, since I can't really explain the mathematically abstract nature of modern physics to someone who's insistent on acting incredulous towards any theory that doesn't make sense in concrete "common sense" terms. Since you seem more well-versed in modern physics than colorspace, a discussion of what you find implausible about this type of model might be more fruitful, if you have the time and are so inclined (if not, no problem).

I'm willing to spend time trying to figure out what you're saying unless it involves Many Worlds. The reason I dismiss Many Worlds is that if it's true, there's no way to do science. That is, if all possible outcomes are always realized, there are universes in which the participants don't get the right statistics, i.e., those that are dictating the split rates. And, there's no way any participant in any of the splits can know whether his results are the "correct" results or not. Therefore, you can't do science.

But, anyway, if you're not going to use Many Worlds, go ahead and try to explain your model.

 

[akhmeteli]

With all due respect akhmeteli, to a layman like me, this looks like a "beat around the bushes"...?

The title of your paper is: "IS NO DRAMA QUANTUM THEORY POSSIBLE?"

I could be wrong, but I interpret "NO DRAMA QUANTUM THEORY" as no "spooky action at a distance", i.e. local realism.

Not just that. The goal is described in the first paragraph you quote: “Something as simple (in principle) as classical electrodynamics - a local realistic theory described by a system of partial differential equations in 3+1 dimensions, but reproducing unitary evolution of quantum theory in the configuration space”. Simplicity of the model was extremely important.

But then you say:
(My emphasis)

In Section 5, you state:
I take for granted that this is the (calamitous) typo??(My emphasis)

Yes, it is. Sorry about that.

To me this looks like a not very fair 'mixture' of; personal speculations + bogus statements + others statements concerning the current status of EPR-Bell experiments, resulting in the stupendous conclusion that Bell "inequalities cannot be violated either in experiments or in quantum theory" ...!?

“not very fair 'mixture'…, bogus statements” –I cannot meaningfully discuss your personal opinions until you give some reasons for them. If you mean the following phrase is “unfair” or “bogus”: “there seems to be a consensus among experts that "a conclusive experiment falsifying in an absolutely uncontroversial way local realism is still missing".”, then I quoted Genovese , Shimony, Aspelmeyer and Zeilinger to support that. I guess these people are indeed “experts”. On the other hand, I just don’t know any responsible and knowledgeable people who would state that there have been any Bell experiments without loopholes. If you know such people, quote them. Maybe you know somebody who knows something that Genovese, Shimony and Zeilinger don’t know about Bell experiments.

As for the “stupendous conclusion”, strictly speaking, there is no such “conclusion” as “Bell "inequalities cannot be violated either in experiments or in quantum theory"”, there is actually the following statement, which you quote earlier: “there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory.” This is a very different statement, and I support it with the relevant arguments.

And how on Earth is this 'compatible' with your initial statement:
??

And how on Earth is it “incompatible”? I insist that I said “little, if anything, new … about the Bell theorem”, as I mostly outlined other people’s arguments, and I insist that the “article is not about the Bell theorem”, it is about a specific model. I just could not offer a local realistic model and avoid a discussion of the Bell theorem.

I trust in RUTA (Mark Stuckey). He’s a working PhD Professor of Physics:

This is no place for a pissing contest, but if you wish to know more about my background, let me know, and I’ll send you a PM.

(My emphasis)

Again, with all due respect, Ruta is not the only one to go to conferences on foundations of quantum theory, and my impression is somewhat different. Maybe we go to different conferences?:-)
Anyway, these issues are not decided by popular vote. For example, as far as I understand, there was a consensus in 1952 that hidden variable theories are not possible, but Bohm’s work proved otherwise. I like this saying: “It is difficult to make forecasts, especially for the future”:-)

I looked at http://www.akhmeteli.org/" and there are no references at all...?

References to what? If for peer reviewed articles, let me know, and I’ll PM you.

To me, this looks like "personal speculations", and not mainstream physics:

I gave references and arguments in this thread to support these statements. Anyway, which one (or two) of them are you challenging? Let’s talk specifics, not perceptions.

And to be frank, your reasoning also looks dim. You are claiming a Local Realistic Model (LRM) that is not capable of violating Bell's Inequality, but that doesn’t matter, because – "these inequalities cannot be violated either in experiments or in quantum theory".

Again, I’m not saying “they cannot”, I am saying “there are reasons to believe they cannot”, these are very different statements.

Exactly how do you derive "cannot" from your previous statements ...??

Again, I don’t derive “cannot”, I derive “there are reasons to believe they cannot”. Exactly how? Just offering the reasons for that. You challenge my reasons? Again, how about some specifics, rather than perceptions?

 

[akhmeteli]

If the prediction is wrong, then QM is wrong. That's the bold assertion I'm fishing for :-)

I am not sure this is a bold assertion for the reasons given in my post 252 in this thread.

Given the preponderance of experimental evidence

Well, you see "preponderance of experimental evidence". My take is: no violations of the genuine Bell inequalities have been demonstrated. 46 years and counting after Bell. I already offered this quote from Heller's "Catch-22" some time ago:

"I've got just the twelve-year-old virgin you're looking for," he announced jubilantly. "This twelve-year-old virgin is really only thirty-four, but she was brought up on a low-protein diet by very strict parents and didn't start sleeping with men until"

So I am sure all those experiments were "brought up on a low-protein diet by very strict parents".

and the highly contrived nature by which loop holes must exist to explain away violations of Bell inequalities, the foundations community has long ago abandoned any attempt to save local realism.

I respect the foundations community. But when I see that the simple local realistic model of my article (nothing contrived about it) has the same unitary evolution as a quantum field theory, I do become suspicious about quantum magic...

But, you're right, there are no truly "loop hole free" experiments,

Thank you:-) Some otherwise knowledgeable people in this thread vehemently deny that...:-)

Are you talking about the measurement problem?

Yes, I do.

That applies to all QM predictions, not just those that violate Bell inequalities.

Yes, but Bell takes the postulates of standard quantum theory to the extreme. So do I get it right that you agree with both of the following points? :-)

1) There is no experimental evidence of violations of the genuine Bell inequalities so far;
2) Proofs of the Bell theorem use two mutually contradicting postulates of the standard quantum theory (unitary evolution and projection postulate) to prove that the Bell inequalities are indeed violated in quantum theory.

 

[akhmeteli]

P.S. akhmeteli


It would be interesting to hear your view on this:

I don't quite get it - I give this very Shimony's quote in my article. So my opinion is the same: this quote confirms that there have been no loophole-free demonstrations of violations.

And while you’re at it: Could you please explain why not one (1) EPR-Bell experiment so far has clearly favored Local Realistic Theories? Not one (1).

What would you need to say that an experiment clearly favors local realistic theories? A discrepancy with quantum theory? But quantum theory is a damn good theory, furthermore, I believe unitary evolution of quantum theory is precisely correct, and we will not see any discrepancy with it for the next 200 years:-) As for the projection postulate... I don't quite know, maybe it is a good approximation, maybe decoherence masks discrepancy with the postulate, but I don't really care, because the projection postulate clearly contradicts unitary evolution, so one of these principles will be found deficient eventually.

I would also add that the entire body of Bell experiments does provide some support to local realistic theories as no genuine violations have been found yet, many years after Bell.

And, if you have some extra spare time: Could you also explain how nature is providing the "detection loophole", which is regarded as the most 'severe'. I mean, if you look at this slide from Alain Aspect, it’s clear that this "magic LRM function" must be wobbling between "too much" and "too little" to provide the measured data. And last but not least, this "magic LRM function" must KNOW which photons are entangled or not?? (Looks like a very "spooky function" to me... )

I don't know. I cannot offer any specifics here. But when I see that a simple local realistic model has the same unitary evolution as a quantum field theory, I conclude that LR models can emulate much more than we can imagine.

 

[zonde]

So, QM is alright as long as you don't have entangled states? Restrictions on applicability are acceptable when a theory is superceded, e.g., Newtonian dynamics is ok when v << c and was superceded by SR to account for v ~ c, but no one has a theory superceding QM that gets rid of its entangled states. And, unlike v ~ c prior to SR, we have the means to create and explore entangled states and all such experiments vindicate QM.

No, zonde, this is not a mere restriction on the applicability of QM.

Absence of absolute preferred frame for electric and magnetic fields was recognized before SR. And there were experiments that explored duality of electric and magnetic fields.
SR does not appeared in empty place without any evidence about shortcomings of existing models. The same for GR.

As to QM existing experiments of entangled photon states take prediction about perfect correlations for matching measurement settings as given while there is no good evidence about it. So there is no viable alternative to QM with that assumption taken as true. But test this assumption and if (when) it fails there might appear new models very quickly.

 

[Dmitry67]

Why if multi-history argument can be used to 'save' LR, it is not used by the die-hard local realists?

 

[DevilsAvocado]

As for the “stupendous conclusion”, strictly speaking, there is no such “conclusion” as “Bell "inequalities cannot be violated either in experiments or in quantum theory"”, there is actually the following statement, which you quote earlier: “there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory.” This is a very different statement, and I support it with the relevant arguments.

Maybe it’s because English is not my native language, but I interpret this quote as: there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory, EVER.

To do statements like this, that is indistinct, is not fair. Also to connect Anton Zeilinger with this ambiguous statement is in fact bogus – because Zeilinger would never say that Bell's Inequalities can NEVER be violated in Bell experiments. Why? How can I be sure?? Well, the man is working every day, as the leading expert, on violating Bell's Inequalities in various Bell experiments. Only a madman would do that, if he already knew that it would NEVER be possible.

Mixing statement as the first, with this one, is just confusing:

there seems to be a consensus among experts that "a conclusive experiment falsifying in an absolutely uncontroversial way local realism is still missing".”, then I quoted Genovese , Shimony, Aspelmeyer and Zeilinger to support that.

Why not include this quote, to give a 'slightly' more unbiased picture?

Stanford Encyclopedia of Philosophy – Bell's Theorem
...
In the face of the spectacular experimental achievement of Weihs et al. and the anticipated result of the experiment of Fry and Walther there is little that a determined advocate of local realistic theories can say except that, despite the spacelike separation of the analysis-detection events involving particles 1 and 2, the backward light-cones of these two events overlap, and it is conceivable that some controlling factor in the overlap region is responsible for a conspiracy affecting their outcomes. There is so little physical detail in this supposition that a discussion of it is best delayed until a methodological discussion in Section 7.

In the light of above, statements like this one can only regarded as wild "personal speculations":

I would also add that the entire body of Bell experiments does provide some support to local realistic theories as no genuine violations have been found yet, many years after Bell.

Personally, I don’t get it. You are claiming that both EPR-Bell experiments and Bell's Theorem are wrong, but you cannot give any specific proofs for that statement:

I don't know. I cannot offer any specifics here. But when I see that a simple local realistic model has the same unitary evolution as a quantum field theory, I conclude that LR models can emulate much more than we can imagine.

How about imagine two polarizers rotating independently random at very high speed between 0º and 360º, separated by 20 km which takes light 66 microseconds, and the final relative angle between the two polarizers are set the last 100 nanoseconds.

Also imagine the relative angle was measured at 22.5º which gives cos^2(22.5) = 85% correlation between Alice & Bob.

Now please tell me exactly how your "LR model" can 'emulate' this experimental fact?

If you can’t deliver an answer – then please stop saying that you have a working "LR model", because you don’t.

 

[DevilsAvocado]

Why if multi-history argument can be used to 'save' LR, it is not used by the die-hard local realists?

Very good question Dmitry67!

 

[DevilsAvocado]

Personally I lean strongly towards MWI type interpretations, I think Occam's razor just says our theoretical assumptions should be fairly simple but it doesn't say that the actual number of entities predicted by the theory should be small (for example, it's no strike against current cosmological theories that they postulate a huge number of stars in the observable universe, and likely many more--perhaps an infinite number--beyond the limits of what we can observe).

Okay, that sounds reasonably fair, but I was thinking more like: Could we really regard MWI as simpler solution than nonlocality?

And I also have some 'difficulty' (in line of RUTA's last post) about all possible outcomes...

As I understand – if there is a slightest possibility for an outcome, it will happen in one of MWI worlds. Therefore, in one of the MWI worlds: I must be a most appreciated Nobel Laureate, happily married to Kim Basinger and Michelle Pfeiffer, and I’m winning on the lottery every day, millions.

Why doesn’t this happen in "our world"?? My "personal luck" is not important – but in all random possibilities that happen all the time, every day, we should see something somewhere that doesn’t fit our "classical assumptions". But we don’t see that...?

Why!?

 

[zonde]

2) Proofs of the Bell theorem use two mutually contradicting postulates of the standard quantum theory (unitary evolution and projection postulate) to prove that the Bell inequalities are indeed violated in quantum theory.

Unitary evolution and projection postulate are not contradicting.
Physical situations that correspond to two different evolutions are different.
In case of unitary evolution all particles from ensemble are preserved.
In case of measurement original ensemble is reduced to subensemble (or split in two or more subensembles).
This is clear difference between unitary evolution and measurement.

Measurement when you measure system that is in eigenstate in respect to operator does not reduce ensemble and that is the only case when measurement can be regarded as unitary evolution.

 

[Dmitry67]

Why doesn’t this happen in "our world"?? My "personal luck" is not important – but in all random possibilities that happen all the time, every day, we should see something somewhere that doesn’t fit our "classical assumptions". But we don’t see that...?

MWI has a problem with Born rule.
It is not clear why, while ALL weird world exist, the ones with low 'intensity' are somehow less important.
My personal opinion is that the Born rule is an artifact created my our consciousness (like the very special moment of time called NOW - so important for us, and having 0 value in block world and 0 explanation in physics). It is also might be a result of entropy of consciousness (or consciousness is not 1 MWI branch, but a set of branches, distinguished microscopically, but changing nothing to state of consciousness)

In any case, it would be very nice to have:
1. An analysis of Bell from MWI point of view
2. Entropy from MWI point of view (any links?)

 

[RUTA]

Unitary evolution and projection postulate are not contradicting.

They are insidiously contradicting. See the chapter on the measurement problem in Quantum Mechanics and Experience, David Z. Albert, Harvard Univ Press, 1992, ISBN 0-674-74113-7.

 

[RUTA]

Yes, but Bell takes the postulates of standard quantum theory to the extreme. So do I get it right that you agree with both of the following points? :-)

1) There is no experimental evidence of violations of the genuine Bell inequalities so far;
2) Proofs of the Bell theorem use two mutually contradicting postulates of the standard quantum theory (unitary evolution and projection postulate) to prove that the Bell inequalities are indeed violated in quantum theory.

1) Yes, but the loop holes that exist, if realized in Nature, would mean Nature is extremely contrived -- a giant conspiracy to "trick" us. No one that I know in the foundations community believes this is the case.

2) Yes, but the measurement problem is a problem for QM as a whole and does not allow for the selective dismissal of any particular QM result without impugning all of QM. And, QM works very well even though it's not a rigorously self-consistent formal system (same can be said of QFT).

 

[zonde]

They are insidiously contradicting. See the chapter on the measurement problem in Quantum Mechanics and Experience, David Z. Albert, Harvard Univ Press, 1992, ISBN 0-674-74113-7.

Unfortunately I don't have access to this book but as I understand the contradiction is usually considered to be related to unclear definition of what constitutes measurement.
But I just gave clear distinction between measurement and unitary evolution.
So if you there other considerations or if you don't agree with my definition then maybe you can give more specific comments.

 

[zonde]

1) Yes, but the loop holes that exist, if realized in Nature, would mean Nature is extremely contrived -- a giant conspiracy to "trick" us.

No it it is not contrived. You just take away interference term in equation describing entangled state and you have restored it to product state - not contrived at all, rather very elegant.
Interesting thing is that you can do it physically in experiment by manipulation temporal walkoff.

 

[DrChinese]

So do I get it right that you agree with both of the following points? :-)

1) There is no experimental evidence of violations of the genuine Bell inequalities so far;
2) Proofs of the Bell theorem use two mutually contradicting postulates of the standard quantum theory (unitary evolution and projection postulate) to prove that the Bell inequalities are indeed violated in quantum theory.

Disagree, as we have already been through this many times. There is nothing BUT evidence of violation of Bell Inequalities. To use a variation on your 34 year old virgin example:

Prosecutor: "We found the suspect over the victim, holding the murder weapon. The victim's last words identified the suspect as the perp. The murder weapon was recently purchased by the suspect, and there are witnesses who testified that the suspect planned to use it to kill the victim." Ah, says the defense attorney, but where is the photographic evidence of the crime itself? This failure is proof of the suspect's innocence!

You can always demand one more nail in the coffin. In fact, it is good science to seek it. But the extra nail does not change it from "no experimental evidence" (as you claim) to "experimental evidence". It changes it from "overwhelming experimental evidence" (my claim) to "even more overwhelming experimental evidence".

As to the second of your assertions: how QM arrives at its predictions may be "inconsistent" in your book. But it does not cause a local realistic theory to be any more valid. If QM is wrong, so be it. That does not change the fact that all local realistic theories are excluded experimentally.

 

[RUTA]

No it it is not contrived. You just take away interference term in equation describing entangled state and you have restored it to product state - not contrived at all, rather very elegant.
Interesting thing is that you can do it physically in experiment by manipulation temporal walkoff.

You can prevent or destroy entangled states very easily -- making and keeping them entangled is the difficult part. There is no getting around violations of Bell inequalities by entangled states in certain situations unless you destroy the situations, which is, again, easy to do.

 

[RUTA]

Unfortunately I don't have access to this book but as I understand the contradiction is usually considered to be related to unclear definition of what constitutes measurement.
But I just gave clear distinction between measurement and unitary evolution.
So if you there other considerations or if you don't agree with my definition then maybe you can give more specific comments.

You used the phrase "in the case of measurement." That is the problem, we don't have a definition for what constitutes a "measurement." We know it when we see it, so we know how to use QM, that's not the problem.

I'm not going to type 100 pages of Albert's text explaining exactly how it's a problem. Get the book and read it; maybe someone here can suggest an alternative reading if you can't find Albert.

 

[akhmeteli]

Nowhere in that quote do they imply it is true in general that "if X is true when condition Y but not condition Z holds, and X is also true when condition Z but not condition Y holds, then we can assume X is true when both conditions Y and Z hold simultaneously". Rather they refer to the specific conditions of the experiment when they say "It is very unlikely that such an experiment will disagree with the prediction of quantum mechanics, since this would imply that nature makes use of both the detection loophole in the Innsbruck experiment and of the locality loophole in the NIST experiment." It's quite possible (and I think likely) that the reason they consider it "unlikely" is because a theory making use of both loopholes would be very contrived-looking.

Then maybe you are drawing a distinction that is too fine for me:-). Indeed, your rephrasing of their phrase can be successfully applied to my statement about Euclidian geometry:-) Until you have an actual geometry in your possession, you can also argue that a theory “making use of both loopholes would be very contrived-looking”.

You addressed it by suggested your own model was non-contrived, but didn't give a clear answer to my question about whether it can actually give statistical predictions about experiments so far like the Innsbruck experiment and the NIST experiment

I did not give you a clear answer because I don’t have it and don’t know how to obtain it within a reasonable time frame. You want me to emulate the above experiments in “my” model. Generally speaking, this is a reasonable request. However, so far I can see only one way to address it: approximate the initial state(s) of those experiments by some fields and run the equations of the nonlinear electrodynamics over a relatively long time period and in a relatively large spatial volume (to ensure reasonable separation). Conducting such a numerical experiment in a clean way (and no other way is good enough) does not seem easy. There may also be some other complications with emulating switching detectors “in flight”. This seems like a lot of work, and I certainly have other priorities.
Therefore, so far my reasoning is different. Let me ask you this: if I offered a model that would have the same unitary evolution as quantum electrodynamics, not just “a” quantum field theory, would that suggest that the actual results of past experiments may be successfully emulated in this model? I’ll proceed (or not, depending on your answer) when I have your answer.

(or any experiments whatsoever, see below)

As I said, the model gives predictions for probabilities the same way Bohmian mechanics does that – you yourself described the relevant procedure. So let me ask you another question: do you think that Bohmian mechanics offers expressions for probabilities? If yes, then how “my” model is different from Bohmian mechanics that it cannot give expressions for probabilities? (its locality should not be a problem in this respect). More specifically, charge density can be calculated in my model, and it can be regarded as probability density (up to a certain factor).

--if it can't, then it obviously doesn't disprove the claim that any local realist theory consistent with experiments so far would have to be very contrived!

I contend that, strictly speaking, it does not disprove that claim, but has that claim been ever proven, in the first place? I have not heard about any “proof” of that claim, only some (pretty vague) arguments. Have you? Similarly, “my” model is, if not a “disproof”, an argument against this claim.

OK, but can your model actually give "correct predictions about statistical results" for any actual experiments, or does it only reproduce the unitary evolution? If it can't predict actual real-valued statistics that are measured empirically, as opposed to complex amplitudes, then it isn't a local realist model that can explain any existing experiments

See above, starting with words “As I said, the model gives predictions”.

(you may be able to derive probabilities from amplitudes using many-worlds type arguments, but as I said part of the meaning of 'local realism' is that each measurement yields a unique outcome)

Again, as I said, “local realism” does not necessarily require that “each measurement yields a unique outcome” (see also below), and I don’t need any “many-worlds type arguments”.

Suppose we do a Wigner's friend type thought-experiment where we imagine a small quantum system that's first measured by an experimenter in an isolated box, and from our point of view this just causes the experimenter to become entangled with the system rather than any collapse occurring. Then we open the box and measure both the system and the record of the previous measurement taken by the experimenter who was inside, and we model this second measurement as collapsing the wavefunction. If the two measurements on the small system were of a type that according to the projection postulate should yield a time-independent eigenstate, are you claiming that in this situation where we model the first measurement as just creating entanglement rather than collapsing the wavefunction, there is some nonzero possibility that the second measurement will find that the record of the first measurement will be of a different state than the one we find on the second measurement? I'm not sure but I don't think that would be the case--even if we assume unitary evolution, as long as there is some record of previous measurements then the statistics seen when comparing the records to the current measurement should be the same as the statistics you'd have if you assumed the earlier measurements (the ones which resulted in the records) collapsed the wavefunction of the system being measured according to the projection postulate.

Sorry, JesseM, I cannot accept this argument. The reason is as follows. If you take unitary evolution seriously (and I suspect you do), then you may agree that unitary evolution does not allow irreversibility, so, strictly speaking, no “record” can be permanent, so a magnetic domain on a hard disk can flip, furthermore, ink in a lab log can disappear, however crazy that may sound. If you challenge that, you challenge unitary evolution, if you challenge unitary evolution, there’s little left of quantum theory. Furthermore, in our previous discussion, I argued that even death (we were talking abot Schroedinger’s cat), strictly speaking, cannot be permanent because of unitary evolution and the quantum recurrence theorem. A superposition just cannot be destroyed.

In any case, the projection postulate does not actually specify that each "measurement" must collapse the wavefunction onto an eigenstate in cases where you're performing a sequence of different measurements. The "pragmatic recipe" is entirely compatible with the notion that in a problem like this, the projection postulate should only be used once at the very end of the complete experiment, when you make a measurement of all the records that resulted from earlier measurements.

It is not so important for this thread how the “pragmatic recipe” is used in general, it is important how the projection postulate is used in the proof of the Bell theorem: it is supposed that as soon as you measure the spin projection of one particle, the spin projection of the other particle becomes definite immediately, according to the projection postulate. So the projection postulate is not "only" used here “at the very end of the complete experiment”, so you have highlighted an important point.

I hope I’ll be able to address your other points later.

 

[akhmeteli]

This is how I get it, and I apologize in advance if it’s wrong:

According to akhmeteli, the LRM does not violate the Bell inequalities, but that doesn’t matter much, because according to akhmeteli, there are no experimental evidence of violations of Bell's Inequalities so far, and Bell's Theorem is faulty in using two mutually contradicting postulates of QM.​

If I’m right, it doesn’t impress me... all he’s saying is that EPR-Bell experiments & Bell's Theorem are wrong, without delivering any proofs for that claim.

I would prefer different wordings.

I am not saying that EPR-Bell experiments are wrong, I hope most of them were performed with proper care and professionalism. I am saying (and support this with quotes) that in each and every such experiment there was at least one loophole, therefore, there was no evidence of violations of the genuine Bell inequalities.

I am not quite saying the Bell theorem is wrong. My take is it uses postulates of standard quantum theory to derive some implications. I don't see any holes in the derivation. However, the input postulates are mutually contradictory (I support this statement with arguments and references), so they cannot be true simultaneously.

So, while I agree that no local realistic theory can emulate ALL predictions of standard quantum theory, I argue that this cannot be an argument against local realistic theories as, on the one hand, those predictions are mutually contradictory, on the other hand, in the part that eliminates local realistic theories (i.e. where Bell ineqs are violated) those predictions have no experimental confirmation.

Note that Ruta basically agreed with my points 1) and 2) in his post 618. True, he immediately "butted" his agreement, but I'd say his "buts" are supported by opinions, not by facts.

 

[GeorgCantor]

I am saying (and support this with quotes) that in each and every such experiment there was at least one loophole, therefore, there was no evidence of violations of the genuine Bell inequalities.

Do you know of a totally 100% loophole-free experiement from anywhere in the universe?

 

[akhmeteli]

akhmeteli: My big question for your model is a familiar one. If it is local realistic, can you tell me what the correct (if QM is wrong in this regard) statistical predictions are for coincidences at a, b, c = 0, 120, 240 degrees? Can you supply a dataset which is in indicative of the rules of your model?

Alice:
a b c
+ - +
- + +
- - +
+ - -

... or whatever you imagine a batch of Alices to be, independent of Bob. A local realistic model should be able to provide this. If not, it does not fulfill the claim of being realistic. And please, do not point me to your paper as proof. The proof is in the pudding, and I am looking to taste some.

Please see my reply to JesseM in post 624 in this thread (starting with words "I did not give you a clear answer").

To summarize: yours is a reasonable request, but I cannot address it within a reasonable time frame - seems like a lot of work for this model, and I have other priorities.

 

[DrChinese]

Do you know of a totally 100% loophole-free experiement from anywhere in the universe?

Great point. So there is no evidence for GR either.

There is another issue with akhmeteli's line of reasoning IF CORRECT: there is a currently unknown local force which connects Alice and Bob. This kicks in on Bell tests like Rowe et al which closes the detection loophole. But not otherwise as far as we know.

There is also a strong bias - also previously unknown and otherwise undetected - which causes an unrepresentative sample of entangled pairs to be detected. This kicks in on Bell tests such as Weihs et al, which closes the locality loophole. Interestingly, this special bias does NOT appear when all pairs are considered such as in Rowe, however, the effect of the unknown local force is exactly identical. What a happy coincidence!

And so on for every loophole when closed individually. All the loopholes have exactly the same effect at every angle setting! And if you leave 2 open instead of 1, you also get the same effect! (I.e. if you leave the locality and detection loopholes open simultaneously, the effect is the same as either one individually.)

Stangely, the entanglement effect (remember that this is just a coincidence per Local Realism) completely disappears if you learn the values of Alice and Bob. Just as QM predicts, but surprisingly, quite contrary to the ideals of Local Realism. After all, EPR thought that you could beat the HUP with entangled particle pairs, and yet you can't!

So to summarize: akhmeteli is essentially asserting that a) 2 previously unknown and otherwise undetected effects exist (accounting for the loopholes); b) these effects are not only exactly equal to each other but are also equal to their combined impact; and c) an expected ability to beat the HUP (per EPR's local realism) has not materialized.

 

[akhmeteli]

Maybe it’s because English is not my native language, but I interpret this quote as: there are some reasons to believe these inequalities cannot be violated either in experiments or in quantum theory, EVER.

Yes, that is exactly what I mean:-)

To do statements like this, that is indistinct, is not fair.

Why so? I give my reasons, don’t I?

Also to connect Anton Zeilinger with this ambiguous statement is in fact bogus

I did not connect Zeilinger “with this ambiguous statement”, I connected him with his unambiguous quote.

– because Zeilinger would never say that Bell's Inequalities can NEVER be violated in Bell experiments. Why? How can I be sure?? Well, the man is working every day, as the leading expert, on violating Bell's Inequalities in various Bell experiments. Only a madman would do that, if he already knew that it would NEVER be possible.

I did not say he does not expect experimental demonstrations of genuine violations. I did not accuse him of being a fan of local realism:-) – nobody of them (Shimony, Zeilinger, Genovese) is. That makes their quotes even more valuable – they all reluctantly admit that there have been no loophole-free demonstrations of violations.

Mixing statement as the first, with this one, is just confusing:

How can this be confusing? Those experts are telling us, mere mortals, that there have been no loophole-free Bell experiments. You are certainly free to disagree with them, but then why don’t you just pinpoint that loophole-free experiment? And it would be most helpful if you could explain how it so happened that Shimony, Zeilinger and Genovese have no knowledge whatsoever about this experiment.
Again, Ruta is no fan of local realism either, but he also admits that there are no such experiments.
So, to summarize, it seems obvious that there have been no such experiments so far (DrChinese will strongly disagree, but let me ask you, DevilsAvocado, what is your personal opinion?) I call this a reason to believe there will be no demonstrations of violations of genuine Bell inequalities ever. I concede that this is no proof, but I honestly cannot understand why this is not a “reason to believe”? As far as my article is concerned, it is my right to indicate that there have been no experiments ruling out local realism, so “my” model has the right to exist right now.

Why not include this quote, to give a 'slightly' more unbiased picture?

I could include it, no problem with that. But is there any mention of an already performed loophole-free experiment in this quote? Again, what is your personal opinion, after all, has there been such an experiment, or not?

In the light of above, statements like this one can only regarded as wild "personal speculations":

I believe numerous failed attempts to build a perpetuum mobile (PM) did give support to the idea that PM is impossible. How is experimental elimination of local realism different? (By the way, I just follow Santos’ reasoning here – of course, you are free to disagree with him, with me or anybody you want).

Personally, I don’t get it. You are claiming that both EPR-Bell experiments and Bell's Theorem are wrong, but you cannot give any specific proofs for that statement:

See my post 625

How about imagine two polarizers rotating independently random at very high speed between 0º and 360º, separated by 20 km which takes light 66 microseconds, and the final relative angle between the two polarizers are set the last 100 nanoseconds.

Also imagine the relative angle was measured at 22.5º which gives cos^2(22.5) = 85% correlation between Alice & Bob.

Now please tell me exactly how your "LR model" can 'emulate' this experimental fact?

Please see my reply to JesseM in post 624 in this thread (starting with words "I did not give you a clear answer").

If you can’t deliver an answer – then please stop saying that you have a working "LR model", because you don’t.

If I could give you an answer, you could ask me another 100 questions, but this is irrelevant to existence of the model. I insist that I offered an LR model having the same unitary evolution as a quantum field theory (QFT). It is certainly important how well or badly this model describes experimental results, but I think the model is important anyway, because it shows how a seemingly nonlocal QFT may be just a disguise for an LR model, so even if “my” LR is not very good at describing experimental results, some of its modifications may fare much better.

 

[akhmeteli]

Unitary evolution and projection postulate are not contradicting.
Physical situations that correspond to two different evolutions are different.
In case of unitary evolution all particles from ensemble are preserved.
In case of measurement original ensemble is reduced to subensemble (or split in two or more subensembles).
This is clear difference between unitary evolution and measurement.

Measurement when you measure system that is in eigenstate in respect to operator does not reduce ensemble and that is the only case when measurement can be regarded as unitary evolution.

If "Unitary evolution and projection postulate are not contradicting", then the results for the subensemble should not contradict the results for the ensemble, however, they do contradict, as, unlike unitary evolution, the projection postulate destroys superposition and introduces irreversibility.