Questioning assumptions behind Bell's and related theorems

In summary: Punting on the definition of reality makes it hard to say much else.In summary, the conversation discusses the mathematical assumptions behind Bell's inequality and how they are being questioned by some authors using a Bohrian-type argument called "the chameleon model". This approach challenges the idea of a single probability space and raises questions about the validity of Bell's argument. However, it is ultimately limited by the lack of a consistent definition of reality.
  • #71
billschnieder said:
This is a red herring.

Not for MorroBay's argument, where he suggests that there is a causal relationship between the observation at one station and the result at the other station.
 
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  • #72
DrChinese said:
I would disagree that "relativity of simultaneity" has anything to do with the perplexing ftl effects. You can see that quantum ordering is irrelevant in many cases in which ordering is absolute. An example is entanglement swapping such as this:

Ah, you're right, there's a bottomless supply of perplexity here :smile:

MorroBay was proposing a causal relationship between the observation at one station and the result at the other, and RoS is (for me, at least, and I expect some company here) a problem for that line of thinking.
 
  • #73
stevendaryl said:
In the reasoning that leads up to Bell's inequality, it is assumed that the choice of the hidden variable is independent of the choice of settings of distant measurement devices. That might not be the case. If the world is deterministic, then the settings of detectors is determined long in the past, and so it is possible to choose the hidden variable in a way that takes into account the future settings. (Actually, there's an interesting--to me--question about whether superdeterminism requires that twin-pair sources and detectors have an overlap in their backward lightcones.

As Accardi proves in the paper cited at the beginning of this thread, the assumption that "the choice of the hidden variable is independent of the choice of settings of distant measurement devices" is the same as the assumption "that the random variables are defined on the same probability space" and that is the only other assumption assumption required to obtain the inequalities together with the assumption of outcomes (+1, -1).
Note that what most people call the "realism assumption", or the "counterfactual definiteness" assumption, are simply variants of this assumption, albeit while using non-standard definitions of "realism" or "CFD". Accardi has distilled it down to the essential mathematical assumption and clearly reveals that you do not need any physical assumption to obtain the inequalities.

Superdeterminism is not the only way to violate the requirement of "the same probability space". QM violates this requirement because non-commuting measurements by definition do not have the same probability space. The authors discuss other mechanisms way more reasonable than superdetermism. See for example the discussion on page 16.

If I may summarize:
* Some λs may not be measurable at certain detector angles, which means non-detection of particles may not be a problem of "detection efficiency" but rather due to the mechanics of the particle detector interaction. In this case, you will never have the same probability space even with perfect detectors.

* The measurement time at given detector angles may a function of both the detector setting and the hidden variable λ, T(α,λ). If T is not a constant you could have a scenario in which for some combinations of setting and λ, the delays are too long that the pairing operation or (coincidence matching) eliminates some λs unfairly.
 
  • #74
Nugatory said:
Ah, you're right, there's a bottomless supply of perplexity here :smile:

MorroBay was proposing a causal relationship between the observation at one station and the result at the other, and RoS is (for me, at least, and I expect some company here) a problem for that line of thinking.

What then does "non-locality" mean if it does not entail "causality"? What is the "mainstream-view" answer to this question?
 
  • #75
billschnieder said:
This is a red herring. If Alice an Bob have synchronized clocks, as they should/do in any such experiment,

And the reply is a blue parrot, synchronized clocks works only within a single inertial frame, unless you want to dispute SR also.

If one wants to do science, I believe one would like the theory to work in all, including difficult, situations. Not only in the living room.
 
  • #76
DevilsAvocado said:
And the reply is a blue parrot, synchronized clocks works only within a single inertial frame, unless you want to dispute SR also.

If one wants to do science, I believe one would like the theory to work in all, including difficult, situations. Not only in the living room.



Are you claiming that if I bury my head in the sand, the relativity of time will not go away? :tongue:
 
  • #77
stevendaryl said:
Those terms being "determinism" and "local realism"? I wouldn't say that they are interchangeable. It just happens to be that for EPR correlations, there is no difference between the two.

Take out the word "local", and that's what I was saying... :biggrin:
 
  • #78
Nugatory said:
Ah, you're right, there's a bottomless supply of perplexity here :smile:

MorroBay was proposing a causal relationship between the observation at one station and the result at the other, and RoS is (for me, at least, and I expect some company here) a problem for that line of thinking.

That's true too! :smile:
 
  • #79
billschnieder said:
As Accardi proves in the paper cited at the beginning of this thread, the assumption that "the choice of the hidden variable is independent of the choice of settings of distant measurement devices" is the same as the assumption "that the random variables are defined on the same probability space" and that is the only other assumption assumption required to obtain the inequalities together with the assumption of outcomes (+1, -1).
Note that what most people call the "realism assumption", or the "counterfactual definiteness" assumption, are simply variants of this assumption, albeit while using non-standard definitions of "realism" or "CFD". Accardi has distilled it down to the essential mathematical assumption and clearly reveals that you do not need any physical assumption to obtain the inequalities.

You need another source for this statement. That paper is not acceptable by forum standards.
 
  • #80
stevendaryl said:
I don't see that counterfactual definiteness is that important, .

i concur.
they bloated it to non realism.
realism is more than definite values.
 
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  • #81
Maui said:
Are you claiming that if I bury my head in the sand, the relativity of time will not go away? :tongue:

Ahh! The Stop Analyzing Next Difficulty experiment!
Of course you're right. Did a quick check and found the preliminary results from The Nevada Synchronized Counter Intuitive Experiment:

10i8c2s.jpg

Bob (sponsored by Taco Bell) looking for the ground breaking results

:biggrin:
 
  • #82
Nugatory said:
MorroBay was proposing a causal relationship

Who the h**l is MorroBay?? :bugeye:

Googled Bell MorroBay causal and got Lolo's Mexican Food - Morro Bay, CA – Yelp?? :grumpy:


(:smile:)
 
  • #83
My apologies for not closing this sooner.
 
<h2>1. What is the Bell's theorem and why is it important in science?</h2><p>Bell's theorem is a fundamental concept in quantum mechanics that states that certain predictions made by quantum mechanics cannot be reproduced by any local hidden variable theory. It is important because it helps to explain the strange behaviors of particles at a quantum level and has implications for our understanding of the nature of reality.</p><h2>2. What are the assumptions behind Bell's theorem and related theorems?</h2><p>The main assumptions behind Bell's theorem and related theorems are locality, realism, and freedom of choice. Locality means that there is no instantaneous action at a distance, realism means that physical properties exist independent of observation, and freedom of choice means that experimenters have the freedom to choose which measurements to make.</p><h2>3. How does Bell's theorem challenge our understanding of reality?</h2><p>Bell's theorem challenges our understanding of reality by showing that the predictions of quantum mechanics cannot be explained by any theory that assumes the existence of local hidden variables. This means that either our understanding of reality is incomplete, or that quantum mechanics is not a complete theory.</p><h2>4. Can Bell's theorem be tested experimentally?</h2><p>Yes, Bell's theorem has been tested experimentally, and the results have consistently supported the predictions of quantum mechanics. These experiments have ruled out the possibility of local hidden variables and have further confirmed the strange behaviors of particles at a quantum level.</p><h2>5. What are the implications of Bell's theorem for future scientific research?</h2><p>The implications of Bell's theorem for future scientific research are significant. It suggests that our understanding of reality may need to be revised, and that quantum mechanics is a fundamental theory that cannot be explained by any underlying classical theory. It also opens up new avenues for research in quantum information and communication, as well as the potential for developing new technologies based on quantum principles.</p>

1. What is the Bell's theorem and why is it important in science?

Bell's theorem is a fundamental concept in quantum mechanics that states that certain predictions made by quantum mechanics cannot be reproduced by any local hidden variable theory. It is important because it helps to explain the strange behaviors of particles at a quantum level and has implications for our understanding of the nature of reality.

2. What are the assumptions behind Bell's theorem and related theorems?

The main assumptions behind Bell's theorem and related theorems are locality, realism, and freedom of choice. Locality means that there is no instantaneous action at a distance, realism means that physical properties exist independent of observation, and freedom of choice means that experimenters have the freedom to choose which measurements to make.

3. How does Bell's theorem challenge our understanding of reality?

Bell's theorem challenges our understanding of reality by showing that the predictions of quantum mechanics cannot be explained by any theory that assumes the existence of local hidden variables. This means that either our understanding of reality is incomplete, or that quantum mechanics is not a complete theory.

4. Can Bell's theorem be tested experimentally?

Yes, Bell's theorem has been tested experimentally, and the results have consistently supported the predictions of quantum mechanics. These experiments have ruled out the possibility of local hidden variables and have further confirmed the strange behaviors of particles at a quantum level.

5. What are the implications of Bell's theorem for future scientific research?

The implications of Bell's theorem for future scientific research are significant. It suggests that our understanding of reality may need to be revised, and that quantum mechanics is a fundamental theory that cannot be explained by any underlying classical theory. It also opens up new avenues for research in quantum information and communication, as well as the potential for developing new technologies based on quantum principles.

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