Random switch setting in bell theorem

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Discussion Overview

The discussion revolves around Bell's theorem, particularly focusing on the concept of random switch settings in experiments involving entangled particles. Participants explore the implications of randomness in measurement settings and how it relates to the statistical outcomes predicted by quantum mechanics versus classical expectations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how random switch settings can lead to all settings occurring equally, questioning the nature of randomness in this context.
  • Another participant explains that while switch settings are random, repeating the experiment many times should yield each setting approximately equally often, referencing the law of large numbers.
  • Further inquiries are made regarding the randomness of switch settings and the states of entangled particles, suggesting a need for clarity on why these elements are treated as random.
  • There is a comparison made between the Bell's theorem experiment and the double slit experiment, indicating a search for parallels in quantum mechanics.
  • A participant summarizes the essence of Bell's theorem, noting the expectation that if properties are determined before measurement, they should obey Bell's inequalities, while quantum mechanics predicts violations under certain conditions.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are multiple viewpoints regarding the interpretation of randomness in switch settings and the implications for quantum mechanics versus classical interpretations.

Contextual Notes

Some participants reference statistical properties and inequalities related to Bell's theorem without resolving the underlying assumptions about the nature of randomness and measurement in quantum experiments.

rajeshmarndi
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I was trying to understand Bells theorem and I found this site
http://www.upscale.utoronto.ca/PVB/Harrison/BellsTheorem/Analogy.html
easy to understand.

I found the "The Second Analogy: More Boxes" in it easy to grasp. But one thing I didn't understand in it, where it uses the word random and expect all possible setting occur equally. Like, here it says,

"But the switch settings are made at random, so we expect each of the six possible results in the above table to occur with equal frequency. So both lights flash the same color one-third of the time."

Here when we say the switch setting are random, then how is it, that all possible setting occur equally. When it is random, it is possible, only one switch setting can occur all the time OR how is it that all possible setting occur equally?

Thank you.
 
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If the switch settings are random and you repeat the experiment many times, you will expect see to all settings about equally often - google for "law of large numbers". It's not necessary that they all occur exactly the same number of times to see a violation of the inequality.
 
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Nugatory said:
If the switch settings are random and you repeat the experiment many times, you will expect see to all settings about equally often - google for "law of large numbers". It's not necessary that they all occur exactly the same number of times to see a violation of the inequality.
Thanks for the reply.
Why do we take switch setting at random and also why are the three different state of particles(here speed, size and shape) are also random?
The device can also record the state of the entangled particles created and the switch setting. So that later it can be checked what was going on.

Also is this experiment similar to double slit experiment?

I understand bell's theorem is all about proving einstein idea and entanglement(quantum physics). For e.g according to quantum physics when pair of object are entangled, say a pair of gloves i.e if one is right hand then the other will be left hand. According to QM the other gloves is not determined before one of the gloves is checked. But according to einstein, they both are determined before the experiment is done.
 
Read through the material here: http://www.drchinese.com/Bells_Theorem.htm

The essential point of Bell's theorem is that if the properties of both members of the entangled pair are determined before the measurement (as Einstein and many others expected) then the results of randomly chosen measurements of a large number of pairs will have certain statistical properties: they will obey Bell's inequalities.

Quantum mechanics predicts that under certain circumstances when there are (at least) three possible measurements, the results will violate the inequalities.
 

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