What do violations of Bell's inequalities tell us about nature?

[stevendaryl]

As rubi and morrobay point out, there are papers that come out the other way on the subject. I.e. that violations of Bell Inequalities indicate it is local non-realism that should be selected. Here is once example:

http://arxiv.org/abs/0909.0015

Abstract:

"It is briefly demonstrated that Gisin's so-called 'locality' assumption [arXiv:0901.4255] is in fact equivalent to the existence of a local deterministic model. Thus, despite Gisin's suggestions to the contrary, 'local realism' in the sense of Bell is built into his argument from the very beginning. His 'locality' assumption may more appropriately be labelled 'separability'. It is further noted that the increasingly popular term 'quantum nonlocality' is not only misleading, but tends to obscure the important distinction between no-signalling and separability. In particular, 'local non-realism' remains firmly in place as a hard option for interpreting Bell inequality violations. Other options are briefly speculated on. "

The lack of separability in quantum mechanics is reflected in the fact that the wave function for more than one particle is not a function in 3 dimensional physical space, but a function in 3N dimensional configuration space. It's hard to know what "local" means for such a theory.

I don't know how significant this is, but in the Heisenberg picture, where the wave function is static and the operators evolve, all evolution is described by perfectly normal evolution equations involving ordinary 3D space plus time. So that is a sense in which the dynamics of quantum mechanics is perfectly local. Any nonlocality happens when you sandwich an operator between in- and out- states, which isn't something that takes place in time.

 

[billschnieder]

What do violations of Bell's inequalities tell us about nature?

Nothing.

http://neuron2.net/papers/bell.pdf

 

[stevendaryl]

What do violations of Bell's inequalities tell us about nature?

Nothing.

http://neuron2.net/papers/bell.pdf

My feeling is that that paper is either wrong, or tautological. In neither case does it tell us anything about Bell's inequalities.

 

[DrChinese]

My feeling is that that paper is either wrong, or tautological. In neither case does it tell us anything about Bell's inequalities.

For what it's worth, billschnieder is a local realist. His reference does not meet the standards for PF. But as long as everyone knows it, considering this thread is essentially an opinion thread anyway, I guess it can't hurt.

 

[billschnieder]

My feeling is that that paper is either wrong, or tautological...

And you are never wrong or misguided.

 

[nitsuj]

I don't see how 'action at a distance' applies to entanglement in quantum world, even by analogy, where/(if) there is no 'action' or 'distance'. Of course ultramicroscopic particles are subject to other properties dependent on space and time. They are 4-space dependent, but quantum-wise non-local. Or to put it less prejudicially (since 'non-local' has the connotation of being somehow defective, deviant, odd), quantum-entanglement has only one locale.

Of course, there are spins that are not entangled, but I could speculate further that all spin-baggage, correlated or not, is permanently stuck in some cosmic LaGuardia airport.

I've always been in the shallow end with respect to an "understanding" of QM because of this "entanglement" thing. It simply doesn't make sense to me strictly because of [STRIKE]causality[/STRIKE]/localism. So no matter how much I would read, it just wouldn't stick.

This perspective you presented makes so much more sense. Essentially the same as Maui post23.

I feel a little slow, not realizing this horse&carriage arrangement on my own .

I guess to say it different, QM isn't so stupid anymore Thanks!

 

[bohm2]

As rubi and morrobay point out, there are papers that come out the other way on the subject. I.e. that violations of Bell Inequalities indicate it is local non-realism that should be selected. Here is once example:

http://arxiv.org/abs/0909.0015

Leaving aside the issue of whether a local non-separability makes sense consider this quote in the paper you linked:

One sentiment of Gisin’s that I do strongly agree with is expressed in the first paragraph of [1]: “why should one use the word local realism rather than local determinism?” The second term is, after all, far less loaded with metaphysical luggage. The popularity of the first term, despite the vagueness of ‘realism’, is due of course to its introduction by Bell in his famous paper [2] [(no doubt as a homage to the discussion of ‘elements of reality’ in the similarly famous paper of Einstein, Podolsky and Rosen.

Given what has been mentioned previously by ttn, do you still feel like this makes any sense to you? And here's the 1964 Bell paper in your link [reference 2 above]:

On the EPR paradox
http://www.drchinese.com/David/Bell_Compact.pdf

Can you hi-lite a relevant part of Bell's 1964 (reference 2) paper where Bell discusses "local realism" or "realism"?

 

[DrChinese]

Leaving aside the issue of whether a local non-separable theorem makes sense consider this quote in the paper you linked:

Given what has been mentioned previously by ttn, do you still feel like this makes any sense to you? And here's the 1964 Bell paper in your link [reference 2 above]:

On the EPR paradox
http://www.drchinese.com/David/Bell_Compact.pdf

Can you hi-lite a relevant part of Bell's 1964 (reference 2) paper where Bell discusses "local realism" or "realism"?

I realize that a lot of people make a distinction between EPR "realism (or simultaneous elements of reality) and Bell "hidden variables (determinism)". Personally, I use them interchangeably when discussing EPR and Bell. The reason I do that is because Bell's paper is a follow up to EPR (see its title) and therefore one must assume Bell begins where EPR left off.

For all practical purposes: if you have hidden variables that determine the outcome of individual measurements, you also have realism. If there are simultaneous elements of reality, there must be determinism as well. So they seem to act together. Despite all the semantics, I rarely see much difference in application between these.

Bell never spells out what he means by "realism" other than mathematically (see his 14 where he is adopting the EPR definition by inference). I say they are the same (Bell determinism = EPR realism).

As I have discussed with ttn previously, and I think he agrees, EPR effectively says that the existence of elements of reality (considering you have the perfect correlations) implies hidden variables and/or determinism. Of course they also assume (and they say explicitly) there must also be observer independence, as well as locality (no action at a distance). So you end up with a bunch of terms that are closely associated, and it is difficult to embrace one over the other without referring back to EPR or Bell.

Elements of Reality / Realism / Hidden Variables / Causality / Determinism

Observer Independence / Separability

Locality / No Action at a Distance

I have placed terms on lines not trying to be exact, but just to show that you could pick a couple of these terms and end up with a phrase that has probably just by an author at some point or another to describe Bell's result.

 

[1977ub]

Is superdeterminism ever taken seriously in these discussions?
http://en.wikipedia.org/wiki/Superdeterminism

I had a similar thought when I heard about Alain Aspect experiments - I mean however far apart the measurements are being made, you can fit the entire situation in a light cone.

If one is truly serious about determinism, then you can't take too seriously a suggestion that someone is "freely" or "randomly" making a particular measurement!

As "unlikely" as superdeterminism might seem... as time drags on, aren't abandonment of locality or causality even harder to swallow?

 

[DennisN]

Is superdeterminism ever taken seriously in these discussions?
http://en.wikipedia.org/wiki/Superdeterminism

I can only speak for myself; I don't take it seriously. How do you show/falsify superdeterminism? If it can't be evaluated, does superdeterminism have any scientific value? The question of quantum locality/nonlocality has at least a fair chance of being evaluated IMO, but I guess it will take a while.

 

[1977ub]

I can only speak for myself; I don't take it seriously. How do you show/falsify superdeterminism? If it can't be evaluated, does superdeterminism have any scientific value? The question of quantum locality/nonlocality has at least a fair chance of being evaluated IMO, but I guess it will take a while.

Can one show/falsify "free" / "random" measurements? Aren't those the pieces which don't fit in the scientific puzzle?

 

[DennisN]

Can one show/falsify "free" / "random" measurements?

No, and that was actually my point (if this is said in terms of superdeterminism). Therefore I don't see the question [nonsuperdeterminism vs superdeterminism] as scientifically interesting. But I see the question [locality vs nonlocality] as scientifically interesting. But that's only my opinion of course.

 

[1977ub]

No, and that was actually my point (if this is said in terms of superdeterminism). Therefore I don't see the question [nonsuperdeterminism vs superdeterminism] as scientifically interesting. But I see the question [locality vs nonlocality] as scientifically interesting. But that's only my opinion of course.

If one doesn't take too seriously the idea of free or random measurements, is there anything in Bell's inequality to call into question our usual confidence in locality?

 

[stevendaryl]

For what it's worth, billschnieder is a local realist. His reference does not meet the standards for PF. But as long as everyone knows it, considering this thread is essentially an opinion thread anyway, I guess it can't hurt.

I think that it's a matter of opinion what is the best explanation for EPR-type correlations, but it seems to me that the claim made in that paper, that Bell's local realism claim is either false or tautologous, isn't just a matter of opinion. You can show that it's not tautologous by showing how his inequalities are easily violated if we allow for instantaneous action-at-a-distance. Showing that they are not wrong is harder, but Bell's theorem, or related theorems have been investigated by many people over many years.

 

[DennisN]

If one doesn't take too seriously the idea of free or random measurements, is there anything in Bell's inequality to call into question our usual confidence in locality?

(note: I may misunderstand you, and if I do, please be more specific)
Most of this thread we're in is an example that the (Bell inequality) question of [locality/nonlocality] is disputed. I voted "anti-realism" (for these reasons), and I definitely lean towards locality, but I can't yet personally completely rule out nonlocality. I put my faith in future science/experiments to shine more light on the matter.

 

[1977ub]

(note: I may misunderstand you, and if I do, please be more specific)

If you look at the whole experiment as a deterministic process unfolding inside a light cone, and therefore without any particular free/random measurement taking place or even making sense (the very terminology seems to be temporarily setting aside a deterministic view) and then there are the correlated measurements at different locations which are preceded by the only superficially "at the last minute" or "freely" or "randomly" chosen settings on the measuring devices - seen from this perspective, is there anything in the Bell/Alain result which might even lead one to question local causality?

Is (odd? supernatural?) belief in non-deterministic free-will essential to finding Bell's inequality a perplexing challenge to local determinism?

 

[DennisN]

[...] seen from this perspective, is there anything in the Bell/Alain result which might even lead one to question local causality?

I suppose you are referring to some kind of superdeterminism, am I correct? If so, I won't argue for or against your particular questions, maybe someone else here will. As I said I don't consider superdeterminism as scientifically interesting, since I can't imagine any way to test it; IMO it's like a chicken'n'egg thing in this respect. Therefore I see it as a too easy and nontestable way out of the (Bell inequality) question of [locality/nonlocality], which is a question which I on the other hand can imagine we might be able to solve in the future.

 

[Nugatory]

If you look at the whole experiment as a deterministic process unfolding inside a light cone, ... is there anything in the Bell/Alain result which might even lead one to question local causality?

No.

Is (odd? supernatural?) belief in non-deterministic free-will essential to finding Bell's inequality a perplexing challenge to local determinism?

Yes.

However, superdeterminism is subject to two major challenges (as well as the general untestability problem, which is common to all interpretations). The first is the philosophical question of free will versus mechanistic determination; I cannot refute the possibility that my free will is an illusion, but it sure doesn't feel that way to me. This was problem for philosophers and theologians long before there were physicists, and I don't see (Penrose notwithstanding) QM helping any with that argument or vice versa.

Second, even if you're willing to come down hard on the no-free-will side, superdeterminism still has a problem: even when A is in the past light cone of B and C, it's not always plausible that A explains correlations between B and C. Put the source of the entangled pair on alpha centauri, four light years away. Give me a Stern-Gerlach machine, put a second one eight light years away with alpha centauri in the middle. The setting of the distant SG machine will be determined by a random radioactive decay; and the setting of my machine will be made based on where I eat lunch two years before the measurement of the entangled pair.

Am I supposed to believe that something that happened on alpha centauri six years before the measurement (to get into the past light cone of my lunch) and two years before the entangled pair is produced, can influence the settings of the two SG machines? Enough to produce Bell-violating correlations?

There's this tiny dark cave where I can placidly shut up and calculate. I retreated to this cave rather than choose between locality and realism, and superdeterminism isn't going to tempt me out of it.

 

[1977ub]

Am I supposed to believe that something that happened on alpha centauri six years before the measurement (to get into the past light cone of my lunch) and two years before the entangled pair is produced, can influence the settings of the two SG machines? Enough to produce Bell-violating correlations?

Sounds absurd, but it's up against greater absurdity... I think you can't study physics for long without looking at everything more and more in terms of intricate determinism you might not have considered before... I almost can't enjoy any time-travel fiction anymore... characters are trying to work out specific identifiable things that if they go back to such-and-such a time would end up changing the future. I'm always thinking "are you kidding?!" what about breathing? what about just standing there?

I don't feel that firm belief in superdeterminism is superior to shut-up-and-calculate, but I guess before we go off too far believing in violations of cause/locality it seems to me that it would need to be kept in mind as in some ways more plausible. If we are determinists, then we can't be too enamoured in free will! quantum or no quantum.

 

[stevendaryl]

Am I supposed to believe that something that happened on alpha centauri six years before the measurement (to get into the past light cone of my lunch) and two years before the entangled pair is produced, can influence the settings of the two SG machines? Enough to produce Bell-violating correlations?

Yes, that sounds absurd. However, there's something a little strange about the time symmetry of fundamental laws which might be relevant here. A rock smashes a glass bottle, sending shards of glass in all directions. Nothing surprising about this. But if you reverse the direction of time, then it looks like: Bits of glass from many locations are thrown toward a rock in just such a way as to cause the glass to fuse into a bottle and expel the rock. The time reversal sounds like a ridiculous conspiracy theory. But both the forward and backward descriptions are equally valid, according to the laws of physics.

I don't have a well-formed thought to express here, but it seems possible to me that a super-determinism theory, which looks like a conspiracy from the usual point of view, might seem more natural in a time-symmetric description.

 

[Nugatory]

I don't have a well-formed thought to express here, but it seems possible to me that a super-determinism theory, which looks like a conspiracy from the usual point of view, might seem more natural in a time-symmetric description.

That's an interesting thought, and I'm inclined to agree with you... Although I'm also inclined to think that the bolded text should read something like "marginally less unnatural"... It's not going to lure me out of my cave any time soon.

 

[bohm2]

This is an interesting paper relevant to the thread that just came out today. The abstract:

This paper addresses arguments that “separability” is an assumption of Bell’s theorem, and that abandoning this assumption in our interpretation of quantum mechanics (a position sometimes referred to as “holism”) will allow us to restore a satisfying locality principle. Separability here means that all events associated to the union of some set of disjoint regions are combinations of events associated to each region taken separately. In this article, it is shown that: (a) localised events can be consistently defined without implying separability; (b) the definition of Bell’s locality condition does not rely on separability in any way; (c) the proof of Bell’s theorem does not use separability as an assumption. If, inspired by considerations of nonseparability, the assumptions of Bell’s theorem are weakened, what remains no longer embodies the locality principle. Teller’s argument for “relational holism” and Howard’s arguments concerning separability are criticised in the light of these results. Howard’s claim that Einstein grounded his arguments on the incompleteness of QM with a separability assumption is also challenged. Instead, Einstein is better interpreted as referring merely to the existence of localised events. Finally, it is argued that Bell rejected the idea that separability is an assumption of his theorem.

Non-separability does not relieve the problem of Bell’s theorem
http://lanl.arxiv.org/pdf/1302.7188.pdf

 

[morrobay]

Another relevant article with a geometric model/explanation for interpreting spin correlations
www.ejtp.com/articles/ejtpv9i27p111.pdf and
www.arxiv.org/pdf/quant-ph/0005103.pdf

 

[rkastner]

There are different interpretations, but generally violations of Bell's inequalities imply what's already known - that classical mechanics(strict materialism) is just one aspect of reality and so no longer an adequate explanation of observations. As Heisenberg once put it/quoted by Nick Herbert in Quantum Reality/:

"The ontology of materialism rested upon the illusion that the kind of existence, the direct 'actuality' of the world around us, can be extrapolated into the atomic range. This extrapolation, however, is impossible... atoms are not things."

The way to keep the strict materialism intact is by accepting a small conspiracy - superdeterminsim or hidden variables(or to deny interest into the inner workings of reality).

I propose an exploration of Heisenberg's ideas about quantum objects as 'potentia' or 'possibilities' in my new book:

The Transactional Interpretation of Quantum Mechanics: The Reality of Possibility
www.cambridge.org/9780521764155

Introductory and preview material (and a publisher's discount) is on my website,
rekastner.wordpress.com. I welcome questions and comments on this material.

 

[bohm2]

I propose an exploration of Heisenberg's ideas about quantum objects as 'potentia' or 'possibilities' in my new book: The Transactional Interpretation of Quantum Mechanics: The Reality of Possibility www.cambridge.org/9780521764155

Ruth,
From reading some of your papers you seem to argue that locality cannot be saved. (e.g. 'Quantum Nonlocality: Not Eliminated by the Heisenberg Picture). With respect to 'possibilities' or 'potentia', would the views you favour be anything like Gisin's views summarized here:

For me realism means, very briefly, that physical systems possesses properties preexisting and independent of whether we measure the system or not; however these preexisting properties do not determine measurement outcomes, but only their propensities. Accordingly, there are realistic random events that reflect preexisting properties, as required by realism, simply the reflection is not deterministic.

Non-realism: Deep Thought or a Soft Option?
http://www.gap-optique.unige.ch/wiki/_media/publications:bib:nonrealismfinal.pdf

 

[rkastner]

My proposal has some affinity with this quote by Gisin, in the following sense: an offer wave (represented by |X>) is a physical possibility for property X to be actualized. However X can of course be decomposed into other properties (e.g., Yi) as Ʃi <Yi|X> |Yi>. The response by an absorber of adjoint property (confirmation wave) <X|Yi> <Yi| sets up an incipient transaction corresponding to that property, which may be actualized with the weight |<X|Yi>|^2 (i.e. probability).

This is the physical basis of von Neumann's 'Process 1' in which a pure state |X> transitions upon 'measurement' or 'observation' (in the usual parlance) into the mixed state
Ʃi |<X|Yi>|^2 |Yi><Yi|, with one of the |Yi><Yi| being randomly actualized as a property. Note that in this TI process, 'measurement' becomes precisely physically defined and is observer-independent. That problem is resolved by taking absorption (i.e., response of the absorber) into account.

If the intial |X> were responded to by adjoint <X| then that property would be actualized with certainty. However, since this is rarely the case, we don't have a classical type of realism. Also, it's not local wrt spacetime because of the advanced influences establishing the properties.

 

[edpell]

My current thought is that spin involves a unique spatial dimension that is not used by any other physical parameter/feature. The "fourth" dimension is tiny. All spin particles are effectively zero distance for each other. So measuring one and collapsing the state of the pair can be communicated to the second in near zero time as the distance in dimension four is tiny. Problem solved. No magic, nothing out of the ordinary, except for that fourth dimension used by spin. But hey spin has always seemed unique.

 

[Steve Brown]

For me, the philosophical implication of quantum non-locality is that the universe is a single, unified hyperparticle. This conclusion follows from the observation that two remotely separated particles can be in intimate and immediate communication with each other. Hence, they must be two components of a unified entity, connected in a transcendental or hyperspace dimension.

 

[wuliheron]

Since Bell's theorem the mounting evidence supports that quanta are contextual or, in other words, context trumps content. Using the context to define the properties of the individual parts contextual systems can do a complete end run around metaphysics because the context alone suffices to describe everything observable. As a result the same contextual system can have multiple metaphysical interpretations when none is actually needed to explain anything. The drawback for physics is that because indeterminacy can only be elucidated by its context it is a quintessential metaphor with possibly the void as its root metaphor.

Millions worldwide consider their ignorance to be part of the "mother of all" voids believed to be the origin of all that exists and does not exist. The tempting shade of a tree, the silences between the notes of a song, and the calm center of the storm are all believed to be manifestations of a single "great" void that makes everything, including our ignorance, useful and meaningful. Hints of its nonexistent-existence everywhere we look. A mystery that has no properties, obeys no physical laws, and is simultaneously everywhere and nowhere connecting all of life. That might sound like a lot of gibberish about nothing, but it's also a decent description of quantum indeterminacy.

So that's what Bell's inequality implies is that indeterminacy may be indistinguishable from the void. Einstein complained that, "God is subtle, but he is not malicious" to which Allan Watts might have replied, "God is playing peek-a-boo, and she's really good!"

 

[audioloop]

Properties are just predicates, ‘attributes,’ ‘qualities,’ ‘features,’ ‘characteristics,’ not the reality itself.

 

[wuliheron]

Properties are just predicates, ‘attributes,’ ‘qualities,’ ‘features,’ ‘characteristics,’ not the reality itself.

Properties can be treated as variables no different from X and Y and used to indicate whatever you want, but if it isn't useful its of questionable value.

 

[bohm2]

The wave function, at least for people who think (following Bohr) that the wave function provides a complete description of (microscopic) physical reality. It's true, there are people who don't think the wf in ordinary QM should be understood as a beable, as corresponding to some physical reality. The question for them is: what, then, does?

I thought this was an interesting paper in trying to answer this difficulty, a difficulty that was also pointed out by Maudlin that the authors believe they can answer:

Following Jeff Barrett (1999), we define a theory to be empirically incoherent in case the truth of the theory undermines our empirical justification for believing it to be true. Thus, goes the worry, if a theory rejects the fundamental existence of spacetime, it is threatened with empirical incoherence because it entails that there are, fundamentally, no local beables situated in spacetime; but since any observations are of local beables, doesn't it then follow that none of our supposed observations are anything of the kind? The only escape would be if spacetime were in some way derived or (to use the term in a very general sense, as physicists do) 'emergent' from the theory. But the problem is that without fundamental spacetime, it is very hard to see how familiar space and time and the attendant notion of locality could emerge in some way...at least without some concrete proposals on the table...

Suppose then that as far as many quantum theories of gravity are concerned, in various ways, familiar spacetime is not admitted at the fundamental level, putting quantum gravity in violation of Maudlin's dictum, and threatening empirical incoherence. In the next section, we will consider a range of such theories, and observe that the seriousness of these challenges depends a great deal on what they postulate instead of spacetime. Different theories leave more or less of the standard structure of spacetime intact, and so understanding our observations may, in the best case, require only a relatively small shift in our conception of local beables. But we will also see that in theories in which little or nothing of spacetime is left in the fundamental ontology, it still may be the case that the question of deriving some formal structure that mirrors local beables can be answered rather more readily than one might expect. In the final section we will turn to such derivations and address Maudlin's argument that such formal derivations never show that local beables are part an emergent ontology.

Emergent Spacetime and Empirical (In)coherence
http://lanl.arxiv.org/pdf/1206.6290.pdf

Slide presentation:
http://workshops.aei.mpg.de/philQG/Nick.pdf

 

[Quantumental]

I thought this was an interesting paper in trying to answer this difficulty, a difficulty that was also pointed out by Maudlin:

Pointed out by Maudlin? Does that mean he accepts that they have defused his worries?

 

[bohm2]

Pointed out by Maudlin? Does that mean he accepts that they have defused his worries?

Sorry, I changed it so it doesn't appear that it was a Maudlin quote. And I'm not sure if Maudlin accepts it, but I doubt it, although he acknowledges in some of his work that he may come to change his view, with time. But again, that's just my interpretation of his writings/videos.