Quantum Entanglement: Is Spin Truly Random?

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Discussion Overview

The discussion revolves around the nature of quantum entanglement, specifically questioning whether the spin of entangled particles is truly random or if it follows some underlying deterministic pattern. Participants explore implications of Bell's theorem and the concept of superdeterminism in relation to measurements of spin.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants propose that the consistent opposite spins observed in entangled particles suggest a complex algorithmic pattern rather than true randomness.
  • Others argue that this perspective conflicts with Bell's theorem, which challenges local realistic explanations for the observed correlations.
  • A participant introduces the idea of superdeterminism, suggesting that if the observer's choices are also deterministic, then Bell's theorem may not apply.
  • Further elaboration on superdeterminism includes the notion that counterfactual states regarding polarizer settings cannot exist in a deterministic framework, as they would not evolve from the same initial conditions.
  • One participant acknowledges understanding the complexities of the discussion, indicating engagement with the concepts presented.

Areas of Agreement / Disagreement

Participants express differing views on whether the spin of entangled particles is random or follows a deterministic pattern. The discussion remains unresolved, with multiple competing perspectives on the implications of Bell's theorem and superdeterminism.

Contextual Notes

The discussion touches on complex theoretical concepts such as Bell's theorem and superdeterminism, which involve assumptions about determinism and the nature of quantum measurements. The implications of these theories are not fully resolved within the conversation.

ryuunoseika
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Correct me if I'm wrong, but it seems to me that if you split a particle separate the parts and measure their spins only to discover it's always the opposite except when tampered with, that's a sign that said particle's spin isn't truly random and is actually part of some complex algorithmic pattern that happens to be the same in the two particles, not that the two particles are somehow communicating instantaneously. Am i wrong?
 
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That would make sense, apart from a further complication which has to do with the violation of "Bell's theorem".
 
ryuunoseika said:
Correct me if I'm wrong, but it seems to me that if you split a particle separate the parts and measure their spins only to discover it's always the opposite except when tampered with, that's a sign that said particle's spin isn't truly random and is actually part of some complex algorithmic pattern that happens to be the same in the two particles, not that the two particles are somehow communicating instantaneously. Am i wrong?

A complex algorithmic pattern which is the same for the two particles would be a local realistic explanation. Such an explanation cannot be used for an explanation for the violation of Bell's inequality.

See http://ilja-schmelzer.de/realism/game.php" for the slightly more complicate situation which cannot be explained in this way.
 
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It could perhaps work if you assume that the observer is deterministic too and is also part of the algorithm that describes the spins. Then any counterfactual choice of the observer for the setting of the polarizers don't exist and Bell's theorem does not apply because of this so-called "superdetermism" loophole.

This has been argued by 't Hooft. He has argued that keeping everything the same except for the settings of polarizers is unphysical in a deterministic theory. If the universe evolved from some fixed initial conditions to a state in which you are finding yourself measuring spins of entangled particles and have decided to set the polarizers in a certain way, then the hypothetical state in which everything is exactly the same except for the setting of the polarizers, cannot have evolved from that initial condition.

In fact, we can be almost sure that evolving such a state back in time will not yield the big bang, but instead, under the inverse time evolution the universe, it will start to effectively evolve forward in time, in the sense that the entropy will increase. The counterfactual state will be a local minimum of the entropy; evolve it forward or backward in time, and the entropy will increase.

The only way to get a bona fide counterfactual state in which the settings of the polarizers is different, would be to find another initial condition out of a set of "physically acceptable initial conditions" which, when evolved forward in time, would yield the desired counterfactual state.

But this then necessarily implies that many other degrees of freedom are different as well in any such counterfactual state.
 
k, i get it now.
 

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