Can we violate Bell inequalities by giving up CFD?

[Ilja]

I don't deny the existence locality - I am simply saying it doesn't apply to correlated systems because by the definition of correlation if things are correlated what is done in one system is related to what goes on in the other. Include it in locality if you like. The issue however is if you want to keep counter-factual definiteness you must allow superluminal signalling which specifically makes it non-local:
http://drchinese.com/David/Bell_Theorem_Easy_Math.htm

Its reverse - if you want to reject counter-factual definiteness (once it leads to the BI which are violated) you must allow superluminal causal influences.

And the article does not get the main point of the EPR argument:

EPR also said that since it is "unreasonable" to believe that these particle attributes require observation to become real, therefore Hidden Variables must exist. Einstein said: "I think that a particle must have a separate reality independent of the measurements. That is: an electron has spin, location and so forth even when it is not being measured. I like to think that the moon is there even if I am not looking at it." This second part of EPR was accepted by some, and rejected by others including Bell.

No, once we accept the EPR criterion of reality, accept also the observable 100% anti-correlation, and accept Einstein causality, we can prove that the particle has a predetermined spin in all directions, so that we do not have to rely on vague philosophical "I think" feelings.

 

[andrewkirk]

That's an interesting essay. Do you know http://www.cs.ucla.edu/~eb/r384-lnai.pdf?

Thank you atyy. I am not familiar with that Bayesian paper but it looks interesting. I've added it to my reading list.

Andrew

 

[bhobba]

Its reverse - if you want to reject counter-factual definiteness (once it leads to the BI which are violated) you must allow superluminal causal influences.

That's wrong - Bell says you can't have locality and counter-factual definiteness. Counter-factual definiteness is simply a more careful statement of realism - although its slightly different.

Thanks
Bill

 

[andrewkirk]

Its reverse - if you want to reject counter-factual definiteness (once it leads to the BI which are violated) you must allow superluminal causal influences.

That is the reverse of my understanding, and of everything I've ever read on the topic. Why do you think that?
And why do you think anybody would ever want to reject CFD if doing so doesn't solve anything and only creates more problems?

 

[bhobba]

That is the reverse of my understanding, and of everything I've ever read on the topic.

Its wrong. We all make errors and that's all it was. I do things like that all the time.

Thanks
Bill

 

[Derek Potter]

Its reverse - if you want to reject counter-factual definiteness (once it leads to the BI which are violated) you must allow superluminal causal influences.

Not at all. Without CFD, there is no definite state so there is no need for an influence to cause it, whether superluminal or not. In more familiar terms, nothing has to collapse the wavefunction of the detectors if it does not, in fact, collapse.

No, once we accept the EPR criterion of reality, accept also the observable 100% anti-correlation, and accept Einstein causality, we can prove that the particle has a predetermined spin in all directions, so that we do not have to rely on vague philosophical "I think" feelings.

Well those assumptions may entail predetermined spin but EPR violates BI and this proves the opposite. When pitching facts against assumptions I tend to back the facts. One or more assumptions are wrong. Perhaps that is what you mean?

Einstein overstated the case because Heisenberg and Bohr were concocting anti-real theories or weird ideas that observation creates reality. With EPR confirmed by experiment, Einstein would undoubtedly have continued to believe that the moon exists even when he wasn't looking at it, but he would have accepted that it might well be in a positional superposition rather than simply "there".

Of course discussing what Einstein would have thought is counter-factual reasoning too.

 

[stevendaryl]

OK, but the point is obscured if you illustrate non-locality with an example where non-locality is not needed :)

The reasoning goes like this:

• If at some point, Alice knows for certain what Bob's measurement's outcome will be before the measurement takes place, then that reflects a physical fact about Bob's situation.
• Either (A) that fact was true before Alice performed her measurement (and her measurement merely revealed that fact to her), or (B) the fact became true when Alice performed her experiment.
• Choice (A) is a hidden-variables theory, of the type ruled out by Bell's inequality.
• Choice (B) implies that something taking place near Alice (her measurement) caused a change in the facts about Bob.

 

[Ilja]

Not at all. Without CFD, there is no definite state so there is no need for an influence to cause it, whether superluminal or not. In more familiar terms, nothing has to collapse the wavefunction of the detectors if it does not, in fact, collapse.

What means "without CFD" if the CFD is derived?

Well those assumptions may entail predetermined spin but EPR violates BI and this proves the opposite. When pitching facts against assumptions I tend to back the facts. One or more assumptions are wrong. Perhaps that is what you mean?

Of course, one of the assumptions has to be wrong. One is an observational fact, which we can take as given (let others care about loopholes). What remains is:

1.) The EPR principle of reality: If, without in any way disturbing the system, we can predict, with certainty, the result of an experiment, this result is an element of reality even without or before the measurement is done, that means, is CFD.

2.) Einstein causality: The experiment done by Bob does in no way disturb the system measured by Alice.

 

[Ilja]

That is the reverse of my understanding, and of everything I've ever read on the topic. Why do you think that?
And why do you think anybody would ever want to reject CFD if doing so doesn't solve anything and only creates more problems?

CFD in this particular situation is the consequence of the EPR criterion of reality and Einstein causality, together with the observable fact of the 100% anticorrelation.

We would want to reject it, because it would be all we need (together with Einstein causality) to continue with the proof of Bell's inequalities. They are violated (modulo loopholes I ignore), and one way to solve the problem would be to reject CFD in this particular situation.

But if we want to do this, we are faced with the EPR argument, which derives CFD from the EPR criterion of reality and Einstein causality. If one rejects the idea to reject the EPR criterion of reality, you obtain what I have claimed, namely that the rejection of CFD requires the rejection of Einstein causality.

And, indeed, this is the reverse of the understanding of many people, all those who make the quite common error to ignore that determinism is not assumed but derived by the EPR argument, so that they think that simply rejecting determinism would be sufficient to solve the problem.

 

[Ilja]

Counter-factual definiteness is simply a more careful statement of realism - although its slightly different.

Not at all. In particular, de Broglie-Bohm theory is clearly realistic, even deterministic, but there is no CFD in it. The outcomes of "measurements" in dBB are essentially results of interactions, and depend on the configuration of the "measured" system as well as of the "measurement" device. Thus, there is no prediction for outcomes which are not performed, because such unperformed experiments have no configuration of the "measurement" device.

 

[bhobba]

Not at all. In particular, de Broglie-Bohm theory is clearly realistic, even deterministic, but there is no CFD in it.

Hmmm. Actually that's an interesting case. Its the ability to speak meaningfully of the definiteness of the results of measurements that have not been performed. Its real for BM but you can't make definite predictions because of lack of knowledge about initial conditions. In principle you can speak about it, but in practice you can't measure it. It depends on your interpretation of 'speak meaningfully of the definiteness of the results of measurements that have not been performed'. I side with you on that one - but I suspect others may not agree. In other words are measurements that have not been performed measurements in principle or in practice.

Thanks
Bill

 

[harrylin]

[denial of collapse can avoid violating the inequality at spacelike separation.] [..] No, it means that Bob includes Alice as part of his classical apparatus and Alice includes Bob as part of her classical apparatus. So the measurement that is performed is the simultaneous measurement by Alice and Bob. However, using this method to avoid collapse will create a preferred frame, since it takes the frame in which Alice and Bob measure simultaneously. To avoid the preferred frame, one cannot accept the reality of measurements at spacelike intervals. [..]

Such a "preferred frame" is no more preferred than a "rest frame" in SR. In a "rest frame" (also called "inertial system of reference") certain events are simultaneous by mere definition. That doesn't contradict relativity, as any inertial frame will do.
Thus I'm interested in your first remark, can you clarify how denial of collapse can avoid violating the inequality if the two events are simultaneous? I always read the inequality as referring to (at least approximately) simultaneous events. So I find that remark puzzling... Probably you mean something else than how it sounds.

 

[Ilja]

Hmmm. Actually that's an interesting case. Its the ability to speak meaningfully of the definiteness of the results of measurements that have not been performed. Its real for BM but you can't make definite predictions because of lack of knowledge about initial conditions. In principle you can speak about it, but in practice you can't measure it. It depends on your interpretation of 'speak meaningfully of the definiteness of the results of measurements that have not been performed'. I side with you on that one - but I suspect others may not agree. In other words are measurements that have not been performed measurements in principle or in practice.

The point which matters is not that much about "speaking about", but about what we need to prove Bell's theorem.

In dBB theory we can accept the EPR criterion of reality, and it does not follow that the result of the spin measurement has to be predetermined. It depends on the particular hidden configuration of Bobs measurement device, thus, depends also on additional local choices (Bob may have different measurement devices even for the same direction, and choose freely one of them). Thus, the measurement result is essentially created by the measurement. Then, the effective wave function of Alice's part collapses - a well-defined physical effect which follows from putting the configuration of Bobs particle into the shared wave function to obtain the effective wave function of Alice's particle. A procedure which creates the state which Alice will measure, and depends on what happens in Bob's experiment.

So, the EPR criterion is inapplicable - Bob's measurement distorts Alice's system - and so I cannot prove that the spin components are predefined.

 

[bhobba]

The point which matters is not that much about "speaking about", but about what we need to prove Bell's theorem.

My concern is this heading down the semantic argumentation of philosophy route where you simply argue the meaning of words. Personally its really obvious. Its the ability to speak about things independent of measurement. Call it CFD, realism, whatever you like, but you can't have that and absence of superluminal influences.

Thanks
Bill

 

[Ilja]

My concern is this heading down the semantic argumentation of philosophy route where you simply argue the meaning of words. Personally its really obvious. Its the ability to speak about things independent of measurement. Call it CFD, realism, whatever you like, but you can't have that and absence of superluminal influences.

Wrong words are misleading, and a point which has been made by Bell in "Against measurement" is that already the use of the term "measurement" in the quantum context is misleading. And CFD is the thesis that results of measurements are predefined. Which is very different from realism, so that it is quite important that you don't name it realism, but use different words to describe these very different things.

 

[RUTA]

The reasoning goes like this:

• If at some point, Alice knows for certain what Bob's measurement's outcome will be before the measurement takes place, then that reflects a physical fact about Bob's situation.
• Either (A) that fact was true before Alice performed her measurement (and her measurement merely revealed that fact to her), or (B) the fact became true when Alice performed her experiment.
• Choice (A) is a hidden-variables theory, of the type ruled out by Bell's inequality.
• Choice (B) implies that something taking place near Alice (her measurement) caused a change in the facts about Bob.

Nicely said and let me add the following. There is no "fact of the matter" aka "Mermin instruction set" concerning the property of the thing Alice is measuring before she actually performs her measurement, and the same is true of Bob (Choice (A) is ruled out). However, after Alice makes her measurement, there is a "fact of the matter" about what Bob will measure in that same setting. So, as stevendaryl points out, Alice's measurement "caused a change" in the facts about Bob (we're assuming he makes that particular measurement, i.e., I'm not talking about CFD because that is Choice (A) which has been ruled out). But, if the measurements are space-like related, then there is a frame in which Bob's measurement occurs before Alice's and the observers in that frame are equally justified in saying Bob's measurement "caused a change" in the facts about Alice. So, what we have to accept, apparently, is that the events are "co-causal," which means in effect they constitute "one thing." That's the mystery of entanglement -- many experimental outcomes distributed in spacetime all constituting a single, "co-causal" entity.

 

[Nick666]

If it disagrees with experiment then its wrong. In that one statement is the essence of science -

What if the Bell experiments they're doing now with closing all 3 loopholes in the same experiment will not violate the inequalities ?

 

[Ilja]

What if the Bell experiments they're doing now with closing all 3 loopholes in the same experiment will not violate the inequalities ?

This would be fine, the dream of all working theoretical physicists - they would have a chance to find an improvement for the in this case falsified quantum theory.

One could think that I could be unhappy, because this destroys one of my main arguments against standard relativity, in favour of a hidden preferred frame. But, no, I would be happy too.

But unfortunately this is not probable at all.

 

[bhobba]

What if the Bell experiments they're doing now with closing all 3 loopholes in the same experiment will not violate the inequalities ?

That would be very big news and likely be the start of a revolution in physics. But it not very likely - still one never knows.

Thanks
Bill

 

[ShayanJ]

What if the Bell experiments they're doing now with closing all 3 loopholes in the same experiment will not violate the inequalities ?

The comments in the beginning of this lecture were interesting for me. You may want to listen.

 

[RUTA]

There are number of things about your proposed model and RB interpretation in general.
First, entanglement model is not worked out. In p.154-155 setup is described and then when it would be time to introduce particular configuration of "spacetimesource elements" and show how one arrives at expected result there is some handwaving instead.
Second, there was requirement that model has to be local (factorizable, in case bhobba would read this). But as I understand, relations that are fundamental in this model are non-local, right?
Third, to me AGC seems like a cheat (read, non scientific explanation). Is there some motivation why it is reasonable to introduce AGC?
And forth, to me it seems that switching from worldlines to relations as fundamental entities is philosophically fundamental and so extremely radical change that steps out of domain of science.

Oops, I just saw this post. For some reason, I don't get notified of all posts on a watched thread. Thanks for your reply.

1. Entanglement is explained ontologically using Dowker's GHZ set-up in that paper (http://www.ijqf.org/wps/wp-content/uploads/2015/06/IJQF2015v1n3p2.pdf). You can use whatever method you like for computing the probability amplitude of the spacetimesource element associated with a particular outcome. I used the path integral approximation of Sinha, S., & Sorkin, R.: A Sum-Over-Histories Account of an EPR(B) Experiment.Foundations of Physics Letters 4, 303-335 (1991) to compute the amplitude for particular outcomes in the standard EPR-Bell experiment, for example (slides 6-9 of this talk).

2. The spacetimesource element is local in the SR sense, i.e., no superluminal signaling. It is non-local in the geometric sense of a differentiable manifold, but it's called "disordered locality" in that context, not "non-locality." See Caravelli, F., & Markopoulou, F.: Disordered Locality and Lorentz Dispersion Relations: An Explicit Model of Quantum Foam (2012) http://arxiv.org/pdf/1201.3206v1.pdf and Prescod-Weinstein, C., & Smolin, L.: Disordered Locality as an Explanation for the Dark Energy. Physical Review D 80, 063505 (2009) http://arxiv.org/pdf/0903.5303.pdf.

3. We tried to motivate the adynamical global constraint (AGC) over dynamical alternatives in sections 1 and 2 of that paper. Essentially, since we're using ontic structural realism in a block universe, the AGC seemed the simplest way to look for new physics. The AGC is mathematically articulated in section 3 and the corresponding approach to quantum gravity and unification (“An Adynamical, Graphical Approach to Quantum Gravity and Unification,” W.M. Stuckey, Michael Silberstein & Timothy McDevitt. Forthcoming In: Licata, I (ed.) The Algebraic Way: Space, Time and Quantum Beyond Peaceful Coexistence, Imperial College Press, London (2015) http://arxiv.org/abs/0908.4348) has empirical implications (see for example: Stuckey, W.M., McDevitt, T., & Silberstein, M.: Modified Regge Calculus as an Explanation of Dark Energy. Classical and Quantum Gravity 29, 055015 (2012) http://arxiv.org/abs/1110.3973), so I consider it "scientific." That's semantics of course.

4. We chose the ontology of our spacetimesource element because reifying the computational model is typically the simplest way to generate a commensurate ontology. The payoff is a local, realist, psi-epistemic model without CFD or superdeterminism. But, of course, anyone is free to construct their own ontology for our approach, i.e., physics underdetermines metaphysics.

Thanks again for your interest.

 

[atyy]

That would be very big news and likely be the start of a revolution in physics. But it not very likely - still one never knows.

Wow, you are such a sober, serious scientist. Only "likely the start of a revolution"?

 

[Derek Potter]

The reasoning goes like this:

• If at some point, Alice knows for certain what Bob's measurement's outcome will be before the measurement takes place, then that reflects a physical fact about Bob's situation.
• Either (A) that fact was true before Alice performed her measurement (and her measurement merely revealed that fact to her), or (B) the fact became true when Alice performed her experiment.
• Choice (A) is a hidden-variables theory, of the type ruled out by Bell's inequality.
• Choice (B) implies that something taking place near Alice (her measurement) caused a change in the facts about Bob.

Sure. I've said almost exactly the same thing, using the staggered observation scenario. But I put it even more specifically: the sensitivity of Bob's detector is determined by Alice's measurement. I can't see any other way of describing it without abandoning realism. Einstein's sarcasm still stands, made more poignant by the fact it is all confirmed experimentally: there is spooky action at a distance.

 

[zonde]

The comments in the beginning of this lecture were interesting for me. You may want to listen.

The guy have build his model based on "action at a distance" and then from that perspective he is judging why detection loophole isn't likely to be violated. It does not work that way. It's called "assuming the consequent" fallacy.

 

[zonde]

What if the Bell experiments they're doing now with closing all 3 loopholes in the same experiment will not violate the inequalities ?

Nothing. Experiment failed. There are so many ways how you can spoil the experiment that you can't claim you have done it right but QM prediction is just wrong. At least I haven 't seen any proposal for experimental protocol that could in principle claim that QM prediction about violation of Bell's inequalities is falsified.

 

[atyy]

Nothing. Experiment failed. There are so many ways how you can spoil the experiment that you can't claim you have done it right but QM prediction is just wrong. At least I haven 't seen any proposal for experimental protocol that could in principle claim that QM prediction about violation of Bell's inequalities is falsified.

So you think that if the eg. the Aspect experiment had come up with results inconsistent with QM, we would believe QM is right and the experiment had been wrongly performed, like superluminal neutrinos?

 

[Derek Potter]

What means "without CFD" if the CFD is derived?

"without CFD" is what the question asks: "Can we violate Bell inequalities by giving up CFD?"
I don't know what you mean by CFD being "derived". Where is it derived? What is it derived from?

 

[zonde]

So you think that if the eg. the Aspect experiment had come up with results inconsistent with QM, we would believe QM is right and the experiment had been wrongly performed, like superluminal neutrinos?

No, result can be consistent with QM. You just can have poor visibility of correlations so that they do not violate BI.

 

[atyy]

No, result can be consistent with QM. You just can have poor visibility of correlations so that they do not violate BI.

What if you could still show 100% correlation at certain angles?

 

[zonde]

What if you could still show 100% correlation at certain angles?

What do you mean by that? If you have poor visibility you don't have 100% correlation at certain angles. You have 100% correlation modulus visibility at these angles.