Nonlocality - fact or fiction?

[Demystifier]

A short conceptual question for Demystifier:

I'm interested to follow your reasoning and your idea to try to connect to string theory but what about this.

In the Bohmian context and "hidden variables", do you consider these "hidden degrees of freedom" to be objective? Or how about the notion where the distinguishable degrees of freedom is subjective (meaning observer relative)? Does that such a thought make any sense at all from your point of view?

Fra, in the Bohmian context the hidden degrees of freedom are objective. I am not sure that I understand the rest of your question, but just ask yourself what would be an analogous question in classical (not quantum) physics. Whatever your answer in the classical case might be, essentially the same answer can be applied to the Bohmian version of quantum physics as well.

 

[Hans de Vries]

Is that supposed to be in contradiction with something that I said?

Do I really need to say that quantum nonlocalities cannot be used to send instantaneous human-controlled information?

local is inside the light-cone.
non-local is outside the lightcone.

First you say that the viewpoint that both QM and SR are correct is logically inconsistent
and then there is the familiar statement above...

Like: Yes, well, ok, SR is not really violated because of ... Regards, Hans

 

[ueit]

I think that the Bell result disproves ALL local hidden variable theories.

What about superdeterminism? It is a logical possibility, accepted by Bell as such.
A short description about how I think a superdeterministic theory might look like.

Assume that the universe is a sort of deterministic computer game (say chess).
Assume that what we call "entangled" particles are bishops that were at some time on adiacent squares. This will ensure that whenever such bishops are observed they will sit on different colors.

Of course, that cannot explain EPR-type results, but here the superdeterministic idea comes in. There is another constraint that has not been taken into account, the observation itself. Assume that only a king is conscious and can "measure" the bishops. But the king itself cannot move anywhere, its motion is also constrained by the rules of chess. So, it is possible that when this suplimentary set of constraints (those that deal with the act of measurement itself) are accounted for, the EPR correlations might arrise.

So, I think that non-locality cannot be proven because superdeterministic theories are not ruled out by Bell.

 

[ZapperZ]

What about superdeterminism? It is a logical possibility, accepted by Bell as such.
A short description about how I think a superdeterministic theory might look like.

Assume that the universe is a sort of deterministic computer game (say chess).
Assume that what we call "entangled" particles are bishops that were at some time on adiacent squares. This will ensure that whenever such bishops are observed they will sit on different colors.

Of course, that cannot explain EPR-type results, but here the superdeterministic idea comes in. There is another constraint that has not been taken into account, the observation itself. Assume that only a king is conscious and can "measure" the bishops. But the king itself cannot move anywhere, its motion is also constrained by the rules of chess. So, it is possible that when this suplimentary set of constraints (those that deal with the act of measurement itself) are accounted for, the EPR correlations might arrise.

So, I think that non-locality cannot be proven because superdeterministic theories are not ruled out by Bell.

But this is now similar to pre-Bell times where people are arguing things based on simply a matter of tastes simply because each argument cannot be falsified. So unless you have a "super-Bell Theorem" that can make such tests, what you just said here cannot be verified either. This makes any kind of rational discussion on which one is valid or not rather meaningless.

Zz.

 

[ueit]

But this is now similar to pre-Bell times where people are arguing things based on simply a matter of tastes simply because each argument cannot be falsified. So unless you have a "super-Bell Theorem" that can make such tests, what you just said here cannot be verified either. This makes any kind of rational discussion on which one is valid or not rather meaningless.

Zz.

No, I simply pointed out that by rejecting the so-called "statistical independence assumption" Bell's theorem cannot be derived anymore, therefore non-locality cannot be proven using this theorem.
In other words Demystifier should prove that for any possible hidden variable theory the constraints imposed by the theory over the act of measurement itself average to zero. While this is usually assumed to be true it might not be so.

 

[JesseM]

No, I simply pointed out that by rejecting the so-called "statistical independence assumption" Bell's theorem cannot be derived anymore, therefore non-locality cannot be proven using this theorem.
In other words Demystifier should prove that for any possible hidden variable theory the constraints imposed by the theory over the act of measurement itself average to zero. While this is usually assumed to be true it might not be so.

Similarly, it might be true that the laws of physics allow opposite charges to sometimes attract and sometimes repel, but they also conspire to ensure that whenever an intelligent being is measuring them they are always attracting. But these sorts of ideas make nonsense of the idea of discovering the laws of physics via the scientific method, and they also seem to require that the laws of physics have some kind of high-level understanding of what it means for a system to be "measured", as opposed to being interacted with in some other way.

 

[akhmeteli]

Why do you say this? The projection postulate is part of (some interpretations of) quantum mechanics; I don't see where it's used in deriving Bell's inequalities.

Maybe I should have said "Bell theorem", rather than "Bell inequalities", to avoid any misunderstanding. In the Bell theorem, first, the Bell inequalities are derived based on some assumptions, and, second, one proves that these inequalities can be violated in quantum mechanics. The projection postulate is used in this second part of the Bell theorem, when probabilities are calculated.

 

[ueit]

Similarly, it might be true that the laws of physics allow opposite charges to sometimes attract and sometimes repel, but they also conspire to ensure that whenever an intelligent being is measuring them they are always attracting. But these sorts of ideas make nonsense of the idea of discovering the laws of physics via the scientific method, and they also seem to require that the laws of physics have some kind of high-level understanding of what it means for a system to be "measured", as opposed to being interacted with in some other way.

OK, I've used the idea of a conscious observer in my example but this is not necessary at all. You can replace him with an atom or whatever particle the entangled particles may interact with. The relevant properties of that particular atom (position, spin, whatever), on which the measurement result depends, are constrained by the laws of physics. It is not obvious for me that the effect of those constraints averages to zero for every conceivable theory. I agree that it is a nice assumption from a practical stand-point but I don't see it as necessary true.

 

[Demystifier]

So, I think that non-locality cannot be proven because superdeterministic theories are not ruled out by Bell.

I agree. But I don't take superdeterminism seriously, even though I admit that it is a logical possibility.

After all, strictly logically, NO PHYSICAL LAW CAN BE PROVED EVER. But science is not pure logic. When we say that science has proved something, we do not mean it in a strict logical sense.

 

[Demystifier]

local is inside the light-cone.
non-local is outside the lightcone.

First you say that the viewpoint that both QM and SR are correct is logically inconsistent
and then there is the familiar statement above...

Like: Yes, well, ok, SR is not really violated because of ...

If there is reality beyond measurements, then this reality is NOT described by standard quantum theory. You see (unexisting) inconsistencies because you mix standard quantum theory with hypothetical reality. The former obeys the principles of relativity, the latter, if exists, violates them. Don't mix apples with oranges!

 

[Fra]

After all, strictly logically, NO PHYSICAL LAW CAN BE PROVED EVER. But science is not pure logic. When we say that science has proved something, we do not mean it in a strict logical sense.

I think this a good focus. We can not be absolutely confident in anything, not even the laws of physics. I agree completely.

Now what conclusions do we make of this?

My personal action is to turn my attention to the emergence of the laws in the first place, and consider this to be a physical process (as oppose to just some human stuff), and try to ask myself it the confidence in the laws of nature can somehow subjectively be rated. Objective ratings are when a group of observers happens for whatever reasong to agree and the subjective ratings correlate.

I think that is what is going on. And the limited confidence in any law in the first place suggest that observed violations of this law are consistent with observation as long as the information associated with theo observations are not significant to distort the laws to the given confidence.

Thus I think even the laws of physics are in motion. At least the observations of laws are in motion, and that's all I have on my table anyway.

/Fredrik

 

[akhmeteli]

You are supposed to write a rebuttal to all those tons of published papers and argue why their claim of violation of Bell inequalities are not valid, rather than argue them here. Pick up any of these papers, and there are clearly words and phrases to the effect that they claim they observed such violations.

Why should I do it? What's the point? Other people did it, raised the issue of the detection loophole and so on. Furthermore, the arguments of those people were accepted by knowledgeable people. Let me quote Shimony again: "Most of the dozens of experiments performed so far have favored Quantum Mechanics, but not decisively because of the “detection loophole” or the “communication loophole.”" Just think about it, if there was just one repeatable evidence of the Bell inequalities violation, how could it be indecisive? The problem is people typically do not substitute the measured probabilities (correlations) in the Bell inequalities, but first adjust these probabilities using the fair sampling assumption. You call it a violation, I don't. Shimony is not quite happy about loopholes, you are not quite happy (otherwise why would you mention the recent paper on the Bell ineq. violations in the other forum, unrelated to this discussion, if you believe that the evidence of violations is overwhelming as it is?), and yet you want me to be quite happy?
So I don't write rebuttals because others did it better than I could, and I argue here because not everybody here knows the experimental situation as well as you do.

Er.. no. The issue with the detection loophole is that one has to "select" the data and ignores what are called "background" and "missing counts". For some who are arguing that the detection loophole could contribute to the apparent violation of Bell inequality, this "background" and "missing counts" are the crutch that they rest on. This is extremely weak, because if it is true, then even high energy physics will have a problem. But the statistics are what saved both of them. And this is why no one from the "other camp" have even attempted to duplicate the experiment to argue that the detection loophole is what is causing all this. I find that a very glaring absence.

Again, what's the difference what camp an experimental physicist is in, as long as he/she is not a fraudster? Experiments without loopholes are too difficult for the experimental state of the art, so why do you demand that people from the "other camp" do something that nobody can do now? I don't know any other experimental way "to argue that the detection loophole is what is causing all this" but to perform an experiment without loopholes. There is a theoretical way, though: as far as I know, there are local realistic models where the Bell inequalities are not violated, but the fair sampling assumption does not hold. Existence of such models proves that the inequalities "violated" in existing experiments are a far cry from the true Bell inequalities.

You can raise it as much as you like, but if you are arguing that there are no inequalities due to a detection loophole, then you'd better know what "detection" means!

Actually, I don't need to. Because you know what "detection" means, and that's enough for me. Indeed, you know the experimental situation, and, being honest and knowledgeable, you are not trying to state that the Bell inequalities were violated in such and such experiment. You know that it is not so. You are just saying that some manipulations with raw data, such as using the fair sampling assumption, are a necessary evil, that after such manipulations the inequalities are indeed violated, and that eventually violations without loopholes will be demonstrated. However, you do know that no experiments have demonstrated true Bell inequalities (with appropriate spatial separation). If I am wrong, and you believe that there are such experiments, please advise.

The fact that no experiment has ever been done to show exactly where the detection loophole rears its ugly head to influence the outcome should mean something to you.

Maybe it should. But it does not. Maybe the fact that no experiment has demonstrated genuine violations should mean something to you. But it does not. Life is tough.

Yet, you have no reluctance to reject them, even when you just admitted that you're no expert in them. What gave you such powers?

As I did say that "I am not an expert in the Bell inequalities", I assume that by "them" you mean the Bell inequalities, not something else. I am not sure I reject the Bell inequalities, I do agree that they can be derived under some assumptions. I just believe, based on opinions of experts, such as Shimony, that genuine Bell inequalities have not been violated in experiments so far. And I don't feel you disagree. Do I really need any magic powers for such belief? I also doubt there will ever be any such violation demonstrated. But I cannot be sure that won't happen.

Do you also reject the evidence for superconductivity, the presence of quasiparticles in Fermi Liquid Theory, the fractional charges in 2D conductors, the giant magnetoresistance effect, the CP-violation in Kaon decays, etc.. etc? Or are you already experts in those fields as well and have the knowledge to know not to reject them? If you are not, then I don't see you complain about the validity of those phenomena, which means that you depend on experts in those fields to proclaim their validity that allow you to use some of them in your modern electronics. How come you aren't bringing up their validity based on the "philosophy" you are living by? Why only pick on this?

As I said, I rely on experts in many areas, including the Bell inequalities. However, you're right, I am not happy with the Copenhagen interpretation (or any other, to be precise) and feel that there is a glaring contradiction between unitary evolution and the projection postulate. Actually, some results of my own research (and they are not philosophical at all) strongly influence my opinions in this area.

Then you are not having a problem with the experiments, but with Bell theorem itself. This is a separate issue. However, considering that the rigorous formulation and update to Bell has been done, and this includes both the GHZ and the Leggett's inequalities, I'd say that unless you are willing to stick your neck out and publish your own version of why it doesn't do what it says it is doing, then I would say talk is cheap. I would then turn around and apply your own philosophy and ask you why in the world I would accept what you have to say when you have shown nothing. Apply your own principle to what you are doing and you'll realize that what you claim has even less of a leg to stand on than what we know about Bell theorem.
Zz.

I am not sure I have problems with the Bell theorem. As far as I understand, it just states that certain assumptions imply certain inequalities, which are violated in quantum mechanics. I don't see any holes in the proof. However, I have problems with the projection postulate of quantum mechanics (and I said why), which, as far as I can understand, is used in the proof. This is the reason I am not sure any violations will be demonstrated experimentally. Although I can be dead wrong.

And I fully agree with you, I have shown nothing. I am not sure I said anything original. I just said that so far no experiments have demonstrated violations of the genuine Bell inequalities. And I don't have to worry whether you'll accept it or not for the simple reason that you don't seem to dispute that. If I am wrong, and you do dispute it, please advise. You are saying that deficiencies of the existing experiments are not important, and you may well be absolutely right. I am not sure though. Anyway, I don't see how I can "stick my neck" and what I can "publish", as I said nothing new. I can just say "don't kill the messenger". I said pretty much the same as Shimony, but maybe my words were less diplomatic. Why should not I call a spade a spade?

 

[ZapperZ]

Because Shimony's opinion doesn't reflect what the majority of people in this area accept as valid.

You still haven't addressed the two facts that I mentioned earlier. The FACTS were : a set of experiments that closed the detection loophole (but not the locality loophole) claimed to violate the Bell inequality, and the set of experiments that closed the locality loophole (but not the detection loophole) violates the Bell inequality. I asked you if, knowing how these experiments work and how such things are detected, that you think it is simply mere coincidence that they both arrive at the identical conclusion even when they not only use different entanglement/objects to detect, but also different loopholes that were possibly left open. Remember, the "detection" loophole has a different set of statistics that has nothing whatsoever to do with the "locality" loophole. Unless you've never done any experiment in your life, changing two different, independent conditions should not give the same type of results!

And I don't buy this argument that you have no need to the details of the experiment. In fact, I would say that your ignorance of the experiment IS the source of this disagreement. The knowledge of what a photodetector can and cannot do is vital in the degree of confidence in the result. I will put it to you that you have placed your life and the lives of your loved ones on knowledge with the SAME degree of confidence as what we get out of the photodetectors used in these experiments.

It is a FACT that there are no Bell-type experiments being conducted has ever proclaim that these loopholes were responsible for the apparent Bell violation. As an experimentalist, when I look at the body of evidence, and the lack of even ONE experiment to cast a doubt on the conclusion, then there is an overwhelming evidence for the validity of that conclusion. You throw around the word "proofs" as if we have "proofs" in physics. Find me something in physics that has the "proof" that you accept. Again, you have picked on these experiments, while ignoring the fact that other parts of physics have the same "baggage".

You never did tell me whether you accepted all the various phenomena that I listed. Are you experts in those areas as well so much so that you know the intricate details to know that they are valid? If not, then how come you don't complain about, say, the validity of the experiments in superconductivity? why are you sitting back and accepting the conclusions from the experts on this, but not for the Bell-type experiments?

For every Shimony, there are dozens of Zeilingers. Why you accept one, but ignore the others, I have no idea.

Zz.

 

[confusedashell]

Just out of curiosity ZapperZ, which interpretation are you proponent of, if none, which you think are on the right track?

 

[Demystifier]

Just out of curiosity ZapperZ, which interpretation are you proponent of, if none, which you think are on the right track?

Apparently, he didn't voted here:
https://www.physicsforums.com/poll.php?do=showresults&pollid=978

By the way, confusedashell, why didn't you voted for the Bohmian?

 

[ZapperZ]

Just out of curiosity ZapperZ, which interpretation are you proponent of, if none, which you think are on the right track?

Interpretation?

I haven't actually sat down and tried to figure out what "interpretation" I had to adopt. I don't believe, in my line of work, it is necessary. Or maybe I'm with the "shut up and calculate" group. As an experimentalist, I'm guessing that that is the safest bet. I could even say that I have very little patience for any form of discussion where the validity of it can't be distinguished via empirical means. As I've said many times, people are then arguing things based simply on a matter of tastes or personal preference. We might as well argue about our favorite color.

Zz.

 

[confusedashell]

Except, the colors atleast are there:P
Some interpretation is right and most are not (maybe none is right at this point), what I meant is as a experimentalist, your concerned with evidence only, while others are concerned on what the evidence means.
As for the double slit experiment, what would you say "happens" there?
What causes the interference pattern ? or do you just do the experiment and not care at all what the experiment actually is?

 

[ZapperZ]

Except, the colors atleast are there:P
Some interpretation is right and most are not (maybe none is right at this point), what I meant is as a experimentalist, your concerned with evidence only, while others are concerned on what the evidence means.
As for the double slit experiment, what would you say "happens" there?
What causes the interference pattern ? or do you just do the experiment and not care at all what the experiment actually is?

Actually, I care about the theory. It is the theory that puts the experiment into perspective, because what we measure has to be mapped into physical meaning. That's where the theory comes in. So I don't need any "interpretation" to deal with the data. It is what it is, and that's why experimental observation are "facts".

As for the double slit, I tend to lean towards the standard explanation, i.e. by looking at the wavefunction, it implies that the particle goes through both slits simultaneously. But unlike rabid devotees of such views, or rabid devotees of other interpretation, I pledge no allegiance to it. I use it as a "working" view that seems to work! And if you have read many of my posts, I hold the fact that "IT WORKS!" to be a very strong motivator for the validity of something, until something better comes along. All the different interpretations hold no additional advantage to what I need it for, not that I can find any circumstances to need any of them. I do not need to find something that fits into my "world view" or something that makes me "content". Those things have never been a good indicator of what is physically valid.

My favorite color is bright teal green. And "colors" are simply human concepts where the eye-brain system tries to interpret the frequency of light that it is detecting. So are colors really "there"?

Zz.

 

[confusedashell]

Now, don't start going all philosophical "IS THE COLOURS REALLY THERE IN OBJECTIVE REALITY?" yes, they are... not exactly how we percieve them but there are differnt frequencies...
Mine is dark purple by the way... Ecspecially on a hot girls thong...

I agree that some people take the "interpretation" thing to some crazy levels (MWI'ers) how they get the smallest particles in existence to indicate other universes is BEYOND me.
However I still think interpreting the evidence is important, like how observations lead to Darwins theory of evolution who later became the best scientific theory ever known...
Same as, if a interpretation leads to further experiments and evidence, I think it's important.
Just like how Bohm's interpretation lead to Bell's work.
That's pretty good for a interpretation, don't you think?

 

[jtbell]

I agree that some people take the "interpretation" thing to some crazy levels (MWI'ers)

Please, everybody, can we keep discussions of QM interpretations on a non-derogatory level? Otherwise I'm going to be tempted to propose banning such discussions the way we ban arguments over religion.

 

[reilly]

As for the double slit, I tend to lean towards the standard explanation, i.e. by looking at the wavefunction, it implies that the particle goes through both slits simultaneously. But unlike rabid devotees of such views, or rabid devotees of other interpretation, I pledge no allegiance to it. I use it as a "working" view that seems to work! And if you have read many of my posts, I hold the fact that "IT WORKS!" to be a very strong motivator for the validity of something, until something better comes along. All the different interpretations hold no additional advantage to what I need it for, not that I can find any circumstances to need any of them. I do not need to find something that fits into my "world view" or something that makes me "content". Those things have never been a good indicator of what is physically valid.

My favorite color is bright teal green. And "colors" are simply human concepts where the eye-brain system tries to interpret the frequency of light that it is detecting. So are colors really "there"?

Zz.

I tend to agree with ZapperZ on more than a few notions, but not so much on interpretation of the double slit expt. In particular, there's no reason at all to assume that the electron or photon goes through each slit simultaneously. Rather, in my view, the best one can say is that there is a probability of finding a particle in one or the other slit, but not in both. For me, a compelling argument is that no one has, nor is it likely that anyone will measure such a simultaneous passage. Among other things, such a finding would violate charge conservation.

In fact, if you look at the passage of a single particle, how would you compute the probability of detecting such a simultaneous passage? The problems of non-locality are bad enough; finding a particle in two places at the same time would be a mind-blower.

Re colors; I dig green the most. And, ZapperZ, we agree that green is in your head; a product of your perceptual system. Is it real? Who knows, but an assumption that has worked from the earliest days of mankind is, yes we believe that grass is green, and that grass is objectively real. As I've written many times, such an assumption is still the best game in town.
Regards,
Reilly Atkinson

 

[confusedashell]

I remember reading somewhere about the frequencies of colors and a picture of how the colors REALLY are in objective reality without being seen through a human eye.
They were some different, a little more vague, but yet there were colors nontheless..

Reilly, I agree except that it could be a pilot wave carrying the particle, thus particle goes through one slit only as you say and wave goes through both causing interference pattern.

 

[ueit]

I agree. But I don't take superdeterminism seriously, even though I admit that it is a logical possibility.

After all, strictly logically, NO PHYSICAL LAW CAN BE PROVED EVER. But science is not pure logic. When we say that science has proved something, we do not mean it in a strict logical sense.

Sure, but I think you display a too high level of certainty about non-locality. First, non-locality is far from being a physical law, it is a possible interpretation of the physical law. Also, it has not been (and probably cannot be) proven directly (you cannot transfer mass/energy faster than light).

What the physical law says is that there are some correlations between distant measurements. A pre-existing correlation (superdeterminism) is not some absurd, ad-hoc hypothesis but is, I think, a pretty obvious one.

I am now reading Bohm's book, "Wholeness and the Implicate Order" and I found a very nice confirmation of my ideas. He compares particles with vortexes that appear in a stream of water. They seem to have independent existence but this is misleading. You cannot keep 3 vortexes in the same place and move another one independently, you have to change the system as a whole. This is what I think is the main lesson of QM. But this statistical independence is what you need to prove Bell's theorem. No matter how useful it was for science in the past I think it is clearly wrong for QM.

 

[confusedashell]

Apparently, he didn't voted here:
https://www.physicsforums.com/poll.php?do=showresults&pollid=978

By the way, confusedashell, why didn't you voted for the Bohmian?

At the time I had no clue, so it felt natural to vote "something else"

 

[jms5631]

Confusedashell: "However I still think interpreting the evidence is important, like how observations lead to Darwins theory of evolution who later became the best scientific theory ever known..."

I don't know if it's wise to equate evolution with quantum theory in this way. Evolution involves classical concepts, whose implications are easily observable, and whose meaning emerges naturally from the theoretical frameworK: the unification of all life from prokaryotic orgins. Its explanation of how nature works is evident and observable, and its immediate relavance to a description of nature is fully accepted by most intelligent people. Quantum theory, like evolution, has been rigorously confirmed, yet its underlying description of nature remains in doubt. We understand for the most part the language of the theory, yet there is no consensus on how it describes nature. Its use of counter-intuitive and non-classical concepts leaves us bewildered on what kind of reality to assign it, and how to formulate a theory of nature around it. I agree entirely with your assertion about using interpretations to gain new insight, just wonder about the Darwin analogy.

 

[confusedashell]

Only reason I said Darwin's theory of evolution is because it's the most "firm" undeniable theory that we got, yet it was hiiiiiiiiighly controversial when it first came.
Humans always saw that sometihng that exist must have a creator, in which they were completely wrong.
He was told not to think about his observations, God made it, simple.
Kinda like Niels Bohrs claim there is nothing more to say about QM.

 

[Crazy Tosser]

There are no people who don't believe in nonlocality.

 

[JesseM]

There are no people who don't believe in nonlocality.

I think pretty much all mainstream physicists would agree that we can rule out local realism, but many advocates of the many-worlds interpretation would say that it allows you to preserve locality by dropping the requirement that each measurement has a unique outcome (which is part of what is meant by 'realism').

 

[confusedashell]

MWI are the only one who cling to locality, without it their theory falls apart, which it does in any rational mind I think either way, it rejects existence of particles...

 

[akhmeteli]

Because Shimony's opinion doesn't reflect what the majority of people in this area accept as valid.

...

For every Shimony, there are dozens of Zeilingers. Why you accept one, but ignore the others, I have no idea.

Zz.

ZapperZ, thank you very much for your time, your post, and excellent questions. Some of them require and deserve longish answers, which it'll take me some time to prepare (maybe a day or two). Therefore, to make my task more tractable, I won't try to answer all of your questions simultaneously.

So for the moment let us discuss "what the majority of people in this area accept as valid". Of course, I am not going to arrange an election and find out what the majority believes. Fortunately, you made my task easier and named Zeilinger as an example. I was not sure what opinion he has on the issue, so I took a cursory look at his articles in arxiv. I found the most relevant information in an article of 1998 , arXiv:quant-ph/9810080v1 (Phys.Rev.Lett. 81 (1998) 5039-5043). The article is relatively old, so he might have changed his opinion since then. If you have a more recent reference, reflecting such a change, please let me know.

So let me quote Zeilinger:

"All recent experiments confirm the predictions of quantum mechanics. Yet, from a strictly logical point of view, they don’t succeed in ruling out a local realistic explanation completely, because of two essential loopholes. The first loophole builds on the fact that all experiments so far detect only a small subset of all pairs created [6]. It is therefore necessary to assume that the pairs registered are a fair sample of all pairs emitted. In principle this could be wrong and once the apparatus is sufficiently refined the experimental observations will contradict quantum mechanics. Yet we agree with John Bell that
”. . . it is hard for me to believe that quantum mechanics works so nicely for inefficient practical set-ups and is yet going to fail badly when sufficient refinements are made. Of more importance, in my opinion, is the complete absence of the vital time factor in existing experiments. The analyzers are not rotated during the flight of the particles.”"

So Zeilinger et al. describe their experiment aimed at closing the locality loophole and conclude:

"While our results confirm the quantum theoretical predictions [17], we admit that, however unlikely, local realistic or semi-classical interpretations are still possible. Contrary to all other statistical observations we would then have to assume that the sample of pairs registered is not a faithful representative of the whole ensemble emitted.
While we share Bell’s judgement about the likelihood of that explanation [7], we agree that an ultimate experiment should also have higher detection/collection efficiency, which was 5% in our experiment.
Further improvements, e.g. having a human observers choose the analyzer directions would again necessitate major improvements of technology as was the case in order to finally, after more than 15 years, go significantly beyond the beautiful 1982 experiment of Aspect et al [4].
Expecting that any improved experiment will also agree with quantum theory, a shift of our classical philosophical positions seems necessary. Among the possible implications are nonlocality or complete determinism or the abandonment of counterfactual conclusions. Whether or not this will finally answer the eternal question: “Is the moon there, when nobody looks?” [18], is certainly up to the reader’s personal judgement."

Now my conclusion: I failed to find any difference at all between the positions of Shimony and Zeilinger. If you believe there is a substantial difference, please advise. Furthermore, Zeilinger calls the detection and locality loopholes "essential" and says that the issue "is certainly up to the reader's judgement" (OK, here I did cut some corners:-) )

Thus, it looks like experts reluctantly, but kindly allow us, mere mortals, to have our own opinion on this issue. I am certainly going to seize the opportunity.

So maybe the answer to the question "what the majority of people in this area accept as valid" is not as clear-cut as you think?

 

[ZapperZ]

So you accept every single word Zeilinger said, but ignore completely his phrase "however unlikely"? Read what I've written and see if this is familiar with what I've been trying to argue.

Read all the papers by Zeilinger related to the GHZ inequality.

I can double check all the published papers that I've printed on this in my office on Monday and will give you all the quotes that you'd want.

Zz.

 

[confusedashell]

What I have never understood is how people rather cling to locality than realism?
WTF does locality matter if the worlds not real anyway?

I agree nonlocality is a strange fact, but quantum mechanics are strange...
I'm sure even Einstein (if alive) would reject locality after Bell.
I think it's time for the physics society to do exactly that, I would think anyone who can even spell realism, would never reject it.
I just think the physicists are wasting time trying to search for locality after sooo many experiments carried out shows clear nonlocality.

What is it about nonlocality that repulses people anyway?
Our macroscopic world still remains local, and it's not like we can "use it" for anything, except understand nature as science was once about.

 

[ZapperZ]

You might also want to read one of the papers that I had highlighted by Leggett

https://www.physicsforums.com/showpost.php?p=1599072&postcount=63

Even if you allow for non-locality, he is arguing that you still cannot save "realism", without even assuming the validity of the quantum formalism, based simply on the Bell experiments.

Read also the papers on the experimental violation of the Leggett inequality that has an even stringent criteria and have written off a large class of nonlocal realistic model.

https://www.physicsforums.com/showpost.php?p=1518312&postcount=58

Zz.

 

[confusedashell]

This guy heard of bohm?;p he did the impossible:P

I won't waste my time on people arguing for nonrealism

 

[ZapperZ]

This guy heard of bohm?;p he did the impossible:P

I won't waste my time on people arguing for nonrealism

He has a Nobel prize. I'm sure he won't want to waste his time arguing with you.

Zz.