Non-local preparation in entanglement swapping experiments

[gentzen]

Consistent histories doesn't limit us to statistical interpretations if we adopt a Bayesian interpretation of probabilities.

Maybe ask yourself first what a realistic interpretation should provide. If that is missing, then Bayesian probabilities cannot fix that either.

Also note that not being able to provide this is not necessarily a drawback. It would even be incompatible with „Copenhagen done right“, if CH could provide this.

 

[DrChinese]

He doesn't reject Bell's theorem at all. He (and many others) reject the claim that Bell's theorem necessarily implies Einsteinian nonlocal influence.

Consistent histories rejects hidden variables. The point is without λ, you don't have to infer nonlocal influences.

My head is spinning.

I didn’t see the non-hidden variable mechanism that would then need to exist in CH. (We see that in MWI. We see that in retrocausal type explanations.) On the other hand, in your post #69: you say CH is realistic, but denies hidden variables. I am not sure how it can be realistic, which implies a pre-existing and determinate outcome for measurements at all angles independent of a setting elsewhere.

And he does accept a form of “proper” nonlocality. But I am very open to better understanding what is being presented, because it doesn’t seem to fit together as I read it.

 

[Morbert]

Maybe ask yourself first what a realistic interpretation should provide. If that is missing, then Bayesian probabilities cannot fix that either.

By realistic, Griffiths means measurements reveal pre-existing properties of the microscopic system. This would be in contrast with Roland Omnes's position, where macroscopic data is still ultimately what is real.

 

[gentzen]

By realistic, Griffiths means measurements reveal pre-existing properties of the microscopic system.

Griffiths only talks about statistical properties. This is not what most people (including me) mean by realistic. In fact, I claim that CH itself can only talk about statistical properties. This is a nontrivial claim, and it could be wrong. But not in the way Griffiths argues against it, by simply ignoring the issue.

(It could be wrong in Aharonov‘s way, where you actually get rid of the statistics.)

 

[DrChinese]

By realistic, Griffiths means measurements reveal pre-existing properties of the microscopic system. This would be in contrast with Roland Omnes's position, where CH logic is still ultimately only about macroscopic data.

OK, that is pretty much as good a definition as I could compose. The only think I might add is the caveat "the setting of one measuring device cannot influence the reading of another instrument".

So if it is realistic, according to Bell, there must be a nonlocal (instantaneous) mechanism of influence (per your quote of Bell). This is standard deduction from Bell, well-accepted and discussed in thousands of papers. If you deny this, you deny Bell. You can't say "I follow Bell" but then say Bell doesn't apply. If it doesn't apply, you simply don't follow Bell. You can't have your cake and eat it too.

In fact: We know there are no Alice/Bob datasets featuring pre-existing and immutable values in which a) there are perfect correlations at same angles; and b) Bell inequality violations at CHSH angles. I can't understand the point of asserting otherwise. And certainly not after decades of heavy study.

 

[DrChinese]

Griffiths only talks about statistical properties. This is not what most people (including me) mean by realistic.

Help me out: How does use of the word "statistical" change anything? (I am not arguing against you, just trying to understand how that can matter to Griffiths or anybody.)

We must also consider perfect correlations in Bell tests, so the "statistic" in these is 100%... i.e. an element of reality per EPR. There are no hypothetical datasets that reproduce this behavior. Any "realistic" explanation must be able to handle the cases of perfect correlation, as well as CHSH type correlation.

 

[gentzen]

We must also consider perfect correlations in Bell tests, so the "statistic" in these is 100%... i.e. an element of reality per EPR. There are no hypothetical datasets that reproduce this behavior. Any "realistic" explanation must be able to handle the cases of perfect correlation, as well as CHSH type correlation.

CH can handle this 100% case. It is the other cases where it only talks about statistics. And if it could reduce those other cases to 100% cases, then my claim would be wrong. But Griffiths does not even try, or acknowledge the issue.

 

[DrChinese]

CH can handle this 100% case. It is the other cases where it only talks about statistics. And if it could reduce those other cases to 100% cases, then my claim would be wrong. But Griffiths does not even try, or acknowledge the issue.

My point lies in the 100% cases (perfect correlations) where there is no common light cone. That's what we can't get a straight answer about. I've seen how Griffiths "hand waves" away Bell Inequalities, but there aren't any with perfect correlations between remote systems.

 

[gentzen]

My point lies in the 100% cases (perfect correlations) where there is no common light cone. That's what we can't get a straight answer about.

Why not?

I've seen how Griffiths "hand waves" away Bell Inequalities, but there aren't any with perfect correlations between remote systems.

I haven‘t seen him „hand wave“ them away. Griffiths has occasionally weak spots, but nothing serious, especially compared to Goldstein who simply is wrong about CH.

CH is a consistent interpretation, it does not need the support by mumblings of famous physicists like Murray Gell Mann. And the same applies to Griffiths: he has presented CH in easily accessible form multiple times, and that is great. But CH is not dependent on an exegesis of his words, comparable to what is needed to understand Bohr‘s opinion on QM.

 

[DrChinese]

Why not?

I can't answer that, I'm the one asking.

I have provided the most specific examples possible for it to be explained. And I've provided papers by Nobel laureates detailing how there is no common interaction via any form of Einsteinian causality. All I ever see is stuff like "Bell's Inequality doesn't apply" or "we don't know anything until the results are brought together using classical signals". Both of these explanations are meaningless of course.

 

[jbergman]

I can't answer that, I'm the one asking.

I have provided the most specific examples possible for it to be explained. And I've provided papers by Nobel laureates detailing how there is no common interaction via any form of Einsteinian causality. All I ever see is stuff like "Bell's Inequality doesn't apply" or "we don't know anything until the results are brought together using classical signals". Both of these explanations are meaningless of course.

There is a section on the GHZ experiment in Griffith's article, https://plato.stanford.edu/entries/qm-consistent-histories/#GreeHornZeil .

 

[Morbert]

There is a section on the GHZ experiment in Griffith's article, https://plato.stanford.edu/entries/qm-consistent-histories/#GreeHornZeil .

I also discussed it in an earlier thread here

 

[Fra]

(Trying here once more to put the finger on something in a compact way)

In fact: We know there are no Alice/Bob datasets featuring pre-existing and immutable values in which a) there are perfect correlations at same angles; and b) Bell inequality violations at CHSH angles. I can't understand the point of asserting otherwise. And certainly not after decades of heavy study.

IMO, one possible presumed "point" of ("bells theorem does not apply", and we need the classically communicated bsm data) that is implicit in how I've trided to argue on this also in previous threads is this:

• We know after decades that we (anyhthing in the macroscopic environment) have no way of knowing/reading this potentially pre-existing immutable variable that would solve (a), without destroying the "entanglement" and thus the interference pattern. It does not follow logically, that this implies it is not known to the two entangled subsystems, does it? If so, how does it follow? Without physical inquiry? It just means there is no relation to the environment. This is a fallacy IMO.
  
  
• Bells ansatz (and this is at the heart of the divisibility issue that was discussed in the other thread) ASSUMES that a the variable that potentially only the two entangled "subsystems" might know, can still be used to to imagine a hypothetical sample space (that we KNOW can't be sampled! as it destroys entalgnment!!) and divide the process into a partition, where we further assumes that the total results is an average over a process that is assumed to be as if, the hidden variable was known (but just escaped the theorist data). This ansatz IMO follow from no sane logic. It is a simple possibility yes, and the one going into bells ansatz. But the point I tried to make, and I would say also behind the objection of Barandes, is that this is also a fallacy, and the one that creates the confusion. One might argue that this "ansatz" is part of some "realism assumption" that bell had, so that he felt that if this divisibility assumption is not valid, then it does not meet his notion of "realistic". That may well be, but I think it is a limited view on reality in that case. Give or take the definition of "realism" - we still seek an explanation, that we do not have.

/Fredrik

 

[gentzen]

I can't answer that, I'm the one asking.

I feel like having a deja-vu:

I don’t think I know it better than you, I am the one asking.

What exactly is your question? All I can see is an assertion which raises questions regarding your familiarity with CH.

I have provided the most specific examples possible for it to be explained.

It is unclear to me what you expect from CH. What would it mean for you to "explain the most specific examples"? CH is most of all a formalism, which can often be applied to model a given physical situation or to quantitatively describe some actual physical experiment. This is most useful for situations that initially seem paradoxical. The advantage of CH over Copenhagen is that it is more rigorous, but its intuitive explanatory value is often not significantly different.

 

[DrChinese]

There is a section on the GHZ experiment in Griffith's article, https://plato.stanford.edu/entries/qm-consistent-histories/#GreeHornZeil .

Not much to that, it's just the same hand wave as he does to dismiss Bell. That is: he is denying the very realism he is asserting. He just uses his own modified definitions to make them different than usage by everyone else. If you say that a quantum object has objective properties at all times, then Bell and GHZ give that statement a mathematically precise definition. This is well accepted in the scientific community.

Of course, anyone can deny this formulation. But it doesn't really accomplish anything, because you are out on an island with a handful of fellow occupants.

 

[DrChinese]

It is unclear to me what you expect from CH. What would it mean for you to "explain the most specific examples"? CH is most of all a formalism, which can often be applied to model a given physical situation or to quantitatively describe some actual physical experiment.

I gave the experiment (or this, and this) many times. How does CH/Griffiths explain perfect correlation of photons with no common past without invoking nonlocality? How much more specific can I be?

Walk through a specific case a la the Ma paper. Photon 1 is measured |L>, photons 2 & 3 distantly measured indistinguishably |VV>. a) How does distant photon 4 end up as |L> (which is a mutually unbiased basis to V/H)? b) And why would that NOT work if the 2 & 3 photons are distinguishable?