Bell's theorem proof. Does it really proofs anything?

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Discussion Overview

The discussion centers around the implications of Bell's theorem and its associated experiments, particularly regarding the nature of photon spin and the concept of hidden variables. Participants explore the interpretations of experimental results and challenge the conclusions drawn from them, focusing on the relationship between measurement settings and the properties of photons.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants argue that Bell's theorem does not rule out hidden variable theories, suggesting that photons may have predefined spins that are not influenced by measurement.
  • Others contend that any hidden variable model must account for the experimental results, asserting that no such model can match the predictions of quantum mechanics if it assumes independence from measurement settings.
  • A participant proposes that the interpretation of photon spin as an "angle" is misleading, emphasizing that the detectors' settings are what determine measurement outcomes.
  • Concerns are raised about the credibility of sources discussing Bell's theorem, with suggestions to refer to more established literature for accurate understanding.
  • One participant presents an analogy involving scratch lotto cards to illustrate why pre-existing values for quantum variables lead to contradictions with experimental outcomes.
  • Another participant expresses skepticism about the experimental results presented on a specific website, questioning the validity of the interpretations and suggesting that the data may be trivial.

Areas of Agreement / Disagreement

Participants express significant disagreement regarding the interpretation of Bell's theorem and the validity of hidden variable theories. No consensus is reached, and multiple competing views remain throughout the discussion.

Contextual Notes

Participants highlight the importance of specific experimental conditions, such as the placement of sensors and the properties of the materials used, which may affect the interpretation of results. There is also mention of potential misinterpretations of cause and effect in the experimental outcomes.

  • #91
DrChinese said:
You can put pepperoni on mine. And crank up some Steely Dan.

HAHAHA :smile:

YES! Pepperoni + Steely Dan = makes my life worth living!

(sorry for the "sentence violation", going to jail now... :redface:)
 
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  • #92
0xDEAD BEEF said:
What are key points how local-realism explains these experiments?
Photon experiments that test Bell (or CHSH) inequalities relay on so called fair sampling assumption.
The thing is that you don't detect all photons that leave beam splitter but only portion. Typically you have around 10% coincidence rate i.e. you discard 9/10 of detections because you don't have matching detection at the other side.
Idea of fair sampling assumption is that if you would detect them it would not change observed correlations.
So if you assume that detected sample of photons is biased then you have to conclude that photon tests don't prove non-locality.
And I would like to add that this is the only way out of the paradox consistent with local realism.

Btw there was another idea (so called "locality loophole") but it was disproved by experiment with fast switching polarizers.

And you can try to look here as well:
http://en.wikipedia.org/wiki/Loopholes_in_Bell_test_experiments"

0xDEAD BEEF said:
No! My configuration was different. It was - Bob 0, Alisa 90. Photons flying in sometimes have angle 45, so they sometimes must hit ++, --, +-, -+, BUT, we only get +- and -+.
I guess you misunderstood me. My point was that photons flying in sometimes have 45° angle and sometimes different angle.
 
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  • #93
Da Capo: Mamma Mia :bugeye:
 
  • #94
0xDEAD BEEF said:
1. It was - Bob 0, Alisa 90. Photons flying in sometimes have angle 45, so they sometimes must hit ++, --, +-, -+, BUT, we only get +- and -+.

2. What are key points how local-realism explains these experiments?

1. If you know that the photons coming in are polarized at 45 degrees, then they cannot be polarization entangled. And you will get: ++, --, +-, -+.

2. zonde has given a pretty good answer already. This is a very complex question and the answers tend to arouse controversy. But the short answer is that NO local realistic explanation also matches QM. In the view of zonde, local realism + fair sampling can match QM experimentally. This is far from certain (but *may* be possible). What is certain is that such local realism means that a complete sample will not agree with QM. Which follows Bell's Theorem, which essentially states:

No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics.
 

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