Bell's theorem Definition and 96 Threads

  1. H

    Bell's theorem: actual experiment event by event

    So many different experiments, so many variations, so many versions of interpretations and story-telling abstractions. Rather than trying to understand what measurements mean, I would like to know how are they performed. Rather than theoretical, I'm interested in practical aspects of an actual...
  2. B

    Can Bell's Theorem Be Applied to the Question of Free Will?

    Based on the state of science so far, I'm of the opinion that free will does not exist. When I say "free will", I mean that our thought processes and bodies are controlled entirely by natural laws. If our brain is governed by classical principles, then it's completely deterministic. If there are...
  3. jk22

    Does Bell's Theorem Disprove Quantum Mechanics?

    Hi all, in Bell's theorem we consider the measurement of correlation A\otimes B and A\otimes B' Then the theorem states that the "result" for A in both quantities is the same. But does QM not only gives probabilities of the result, hence the result could be in principle different for the...
  4. B

    Bell's Theorem with Easy Math - Stuck

    Hi, I hope there is no issue with me posting this here but I'm stuck trying to get my head around DrChinese's page on Bell's Theorem. "ASSUME that a photon has 3 simultaneously real Hidden Variables A, B and C at the angles 0 degrees, 120 degrees and 240 degrees per the diagram above. These 3...
  5. S

    Is Bell's theorem near-sighted?

    I know Bell has been discussed ad nauseam on these forums, but there's something I'm having trouble coming to terms with: the wording and usage of Bell's theorem seems to be near-sighted. "No physical theory of local hidden variables can ever reproduce all of the predictions of quantum...
  6. S

    Entanglement and Bell's theorem. Is the non-locality real?

    The results of measurements of phase entangled particles together with Bell's theorem provide pretty convincing evidence that the Universe contains non-local interactions. Yet I'm lead to wonder. Let's imagine the usual idealised experimental scenario, where there is an emitter of...
  7. C

    Is there a consensus on Bell's Theorem and its implications?

    Hi. I have read about Bell's Theorem in a couple of popular science books, namely 'Quantum Reality' by Nick Herbert and the recent book by John Gribbin. However, I am still struggling to understand the overall idea. Could anyone explain the concept? Is it taught at university at all...
  8. T

    Scholarpedia article on Bell's Theorem

    Hi everybody. I dropped into Physics Forums for the first time in a while just to see what was going on in one of my old hangouts. It was nice to see about 10 threads raging about Bell's theorem! But perhaps not so nice to see many people, with whom I argued at length in the old days here...
    • ttn
    • Thread
    • article Bell's theorem Theorem
    • Replies: 565
    • Forum: Quantum Physics
  9. G

    A classical challenge to Bell's Theorem?

    This post moved from "Nick Herbert's proof?" https://www.physicsforums.com/showthread.php?t=589134 at the request of the OP. .. Effects without a cause in Herbert's experiment? I presume that you believe that some quantum events have no cause; not classical effects? So I would...
  10. S

    Understanding bell's theorem: why hidden variables imply a linear relationship?

    (Part of) The proof/logic of Bell's theorem goes thus: With the measurements oriented at intermediate angles between these basic cases, the existence of local hidden variables would imply a linear variation in the correlation. However, according to quantum mechanical theory, the correlation...
    • San K
    • Thread
    • Bell's theorem Hidden variables Linear Relationship Theorem Variables
    • Replies: 428
    • Forum: Quantum Physics
  11. S

    Bell's Theorem and the detector

    Edgardo thanks for posting the links to Bell's Theorem. I read the first one and it was a clear description of Bell's experiment. I have a question (or an alternative explanation for the difference in probabilities between mathematical calculations and experimental results in the Bell's...
  12. R

    Bell's Theorem Correlations Velocity

    The observable universe is about 92 billion light years in diameter. It would take 80 years for us just to reach the edge of our galaxy traveling at the speed of light. And there are a magnitude billions of galaxies with the space between them even more distant than within a galaxy. Does it...
  13. A

    Help for a beginner Bell's Theorem

    Help for a beginner...Bell's Theorem Hi guys, I'm definitely a beginner when it comes to quantum mechanics but I've recently been reading about Bell's Theorem and have become intrigued by its implications, specifically the nonlocality principle where electrons seem to be able to communicate...
  14. E

    Bell's Theorem - Easy explained

    Last week I had a blast with reading explanations on Bell's theorem. It was the first time that I've actually understood it. So I wanted to share some websites that explain the theorem in an easy way: 1) Spooky Action at a Distance – An Explanation of Bell’s Theorem by Gary Felder This...
  15. L

    Does Bell's theorem imply stronger or weaker correlation?

    After reading so many threads here about it, I thought I would take a closer look at Bell's theorem. Consider the simple proof presented http://quantumtantra.com/bell2.html" , which I'll summarize below: A light source produces twin state photons, and each photon of the pair goes through a...
  16. S

    Questions about Bell's Theorem

    from http://en.wikipedia.org/wiki/Quantum_entanglement" so far so good. makes sense. the maximum number of mismatches (between A and C) can only be (1/100) + (1/100) = 2% yet in Quantum Entanglement (QE) the number of mismatches is, say, = 4% however if there were hidden variables (in...
  17. H

    Bell's theorem and foundations of statistics

    Dear All, Recently I have published a paper on Bell's theorem ASTP 4(20) 945-949 (2010). One can also find it on arXiv as http://arxiv.org/abs/1012.4990. I am interested in a discussion about the results of the paper. The claim of the paper is that mathematically Bell's theorem is...
  18. R

    Is Bell's Theorem a Valid Solution to the Locality Versus Nonlocality Issue?

    Theoretically, Bell’s theorem can be not be violated by any experiment when applied to a two-valued variables, such as S(T,F), S(H,T), or S(+,-). Whether the measured values are true/false, heads/tails, or up spin/down spin, etc. Bell’s theorem is a mathematical truth, a tautology. If misapplied...
  19. harrylin

    I What is passive locality ? Bell's Theorem.

    What is "passive locality"? Bell's Theorem. In a current thread about explaining Bell's theorem, the question of "passive locality" came up. "Passive locality" was introduced by Nelson in 1986. After discussions with Bell he distinguished between "active" and "passive" locality, arguing...
  20. J

    Discussion of A. Neumaier's claim that classical EM can violate Bell's theorem

    Discussion continued from this post on another thread... Bell's proof does not involve any notions of "particles" or "waves" whatsoever, it only involves observed experimental results combined with the idea that the theory generating them is local realistic. Again, do you agree or disagree...
    • JesseM
    • Thread
    • Bell's theorem Classical Discussion Em Theorem
    • Replies: 8
    • Forum: Quantum Physics
  21. M

    Can grandpa understand the Bell's Theorem?

    Can a grandpa understand the Bell's Theorem? Einstein said that you don't truly understand something unless you can explain it to your Grandma. I think that this should apply also to a grandpa. I am a grandpa who is struggling to understand the Bell's Theorem. I read a number of popular books...
  22. G

    Bell's Theorem, EPRB, QM, spin-1/2 particles, basic arithmetic: In reply

    .. This thread is intended to focus on arithmetic issues, mainly raised by JesseM, vanesch, DrChinese, ThomasT, in the context of: "What's wrong with this local realistic counter-example to Bell's theorem?" https://www.physicsforums.com/showthread.php?t=475076 : For newcomers to the issues...
  23. G

    Bell's theorem and the DrChinese Challenge?

    .. As I read the situation, DrChinese frequently challenges local realists -- of whatever hue -- here, in the Quantum Physics section of PF. As I understand the details: The challenge is delivered in the context of Aspect's experiment, the twinned photons are identically correlated (in the...
  24. G

    Bell's theorem and QM: Peres' conclusion and terminology?

    .. In his text-book "Quantum Theory: Concepts and Methods", Asher Peres (1995) writes: A: "Bell's theorem is not a property of quantum theory." - (p.162, Peres' emphasis). B: "This conclusion can be succinctly stated: unperformed experiments have no results." - (p.168, Peres' emphasis)...
  25. bcrowell

    Joy Christian, Disproof of Bell's Theorem

    Joy Christian, "Disproof of Bell's Theorem" This showed up on the arxiv blog today: Joy Christian, "Disproof of Bell's Theorem," http://arxiv.org/abs/1103.1879 I'm not enough of a specialist to be able to judge the correctness or significance of the result. Comments?
  26. G

    What's wrong with this local realistic counter-example to Bell's theorem?

    This thread is an offshoot of https://www.physicsforums.com/showthread.php?t=403210 -- Joy Christian's disproof of Bell. This thread is a response to: THE SAKURAI LINK (above) SHOULD BE STUDIED AND UNDERSTOOD. This thread also has its basis in the following [somewhat edited] exchange: So the...
  27. 0

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

    So here is this thing that i really really can not agree with (regarding experiments)! What Bell's theory states (correct me, if i am wrong) and experiments with SPOT detector tend to prove is, that measurement of spin of one twin-light photon affects spin of other. Well - if we assume that then...
  28. P

    Question about Dr. Chinese's example of Bell's Theorem

    Hello, this could be a basic question. I saw the link http://www.drchinese.com/David/Bell_Theorem_Easy_Math.htm" on one of the threads. Following the table there the probability of complete match between two detectors happens twice out of 8 times. i.e. 1/4. How how can we say that it...
  29. A

    A Simple Proof Of Bell's Theorem

    I've been following up a lot regarding the fascinating stuff I read here. I recently came across this page; http://quantumtantra.com/bell2.html I know that the author and the other material on that site would be considered new age crackpottery by most here at PF, but anyway, that page...
  30. D

    Hidden variables, Bell's theorem, etc

    Hello all, I'm having a couple of problems with interpretations of Quantum mechanics and just want to summarise my understanding so that it can be verified and/or corrected. Schroedinger's cat leads to the idea of entanglement, namely the observation of one event indicates that other...
    • DeShark
    • Thread
    • Bell's theorem Hidden variables Theorem Variables
    • Replies: 5
    • Forum: Quantum Physics
  31. Z

    Bell's theorem: Local realism v. counterfactual determinism

    This is kind of an offshoot from: https://www.physicsforums.com/showthread.php?t=369328 Assume for a second that the controversial experiments are valid and Bell's theorem is true of the universe. I have often seen the philosophical analysis that if Bell's Theorem is true then either local...
    • zvi
    • Thread
    • Bell's theorem Determinism Local Realism Theorem
    • Replies: 2
    • Forum: Quantum Physics
  32. J

    Bell's Theorem and Counterfactual Definiteness

    Bell's Theorem and "Counterfactual Definiteness" Bell's Theorem and Aspect's experiments pretty much show that quantum theory is nonlocal--the violation of Bell's inequalities show that somehow the wavefunction is acting on the entangled particles faster than c. However, I've heard that...
  33. A

    String theory and Bell's theorem, redux

    I asked this in sci.physics.strings and I haven't gotten an answer yet, so I hope you'll oblige me.
  34. A

    String theory and Bell's theorem

    How can string theory explain the results of Bell inequality experiments and experiments of similar inequalities?
  35. T

    Back up a step, before Bell's theorem

    Hi, think of me as an armchair philosopher I suppose, who is very interested in the science of quantum right now. Bell's theorem led to a finding of nonlocality. I need to back up a step and ask, why. Why is it apparently believed that particles don't have a definite state until they are...
  36. W

    Bell's theorem and Harrison's (2006) inequality

    I'm proposing this new thread as a valid PF-QP contribution; one complying with the relevant rules as I understand them; and the gist of which will be as shown below. However, I would first like to locate a missing draft, as follows: Title: Bell's theorem refuted via* Harrison's (2006)...
    • wm
    • Thread
    • Bell's theorem Inequality Theorem
    • Replies: 101
    • Forum: Quantum Physics
  37. R

    Fun question RE: Bell's Theorem

    If you're not familiar with Bell's inequality, and the subsequent experiment, I suggest perusing over http://www.upscale.utoronto.ca/GeneralInterest/Harrison/BellsTheorem/BellsTheorem.html" But essentially, an experiment is done with counting the number of electrons with certain spins, and...
  38. T

    Bell's Theorem: Griffiths' Probability Density & Indeterministic QM

    I am referring to Introduction to Quantum Mechanics (2nd Edition) by David J. Griffiths, page 425 on Bell's Theorem. Griffiths used a parameter, called \rho(\lambda) as the probability density for the hidden variable. What I don't understand is that the hidden variable was suppose to make...
  39. DrChinese

    Does Bell's Theorem apply to non-local HV theories?

    Does Bell's Theorem apply to non-local HV theories? I know that Bell says it doesn't, and he has included logic intended to make separability a requirement. But consider this argument: What does it mean to say there are hidden variables? Einstein said: "I think that a particle must have...
  40. R

    Is There a Flaw in Bell's Theorem?

    John S. Bell's Theorem, from his famous 1964 paper, "proves" that local variables are not sufficient to explain observations predicted by Quantum Mechanics. This is now widely accepted, primarily because the mathematics used is so simple and direct, but his argument is flawed from the very first...
  41. E

    Good paper(s) on Bell's theorem

    Hello all, When I read the original papers by EPR and Bell here http://www.drchinese.com/David/EPR_Bell_Aspect.htm I didn't understand them. But I found a paper that explains Bell's theorem quite good: Daniel M. Greenberger, Michael A. Horne, Abner Shimony, Anton Zeilinger "Bell's...
  42. DrChinese

    Bell's Theorem and Negative Probabilities

    Bell's Theorem and Negative Probabilities Introduction ============ Author's note: This post is based on Bell's Theorem (1). I have reformulated the presentation to make it a little easier to see that "Negative Probabilties" are a seemingly paradoxical consequence of his work. The Bell...
  43. W

    Challenging Bell's Theorem: A Critical Analysis of the Assumptions and Errors

    We've been trialling our website over the past year and have now settled on a preliminary format. Much more material is to be added (and much to be rewritten in our new format) so many links are currently incomplete. However, given recent comments on PF, we thought it might help to make two of...
  44. E

    What are hidden variables and the significance of Bell's Theorem?

    I have found a site that derives Bell's inequality The number of objects which have parameter A but not parameter B plus the number of objects which have parameter B but not parameter C is greater than or equal to the number of objects which have parameter A but not parameter C. And I...
  45. N

    Dopey Question about Bell's theorem.

    For context I'm looking at: http://www.mtnmath.com/whatrh/node80.html Bell's theorem suggests that a hidden variable λ cannot exist, but, at least the version above makes the assumption that Λ (the set of all posible values of λ ) is a measurable domain s.t...
  46. cytokinesis

    What is Bell's Theorem and its implications in quantum physics?

    I recently read about Bell's theorem in the book 'The Dancing Wu Li Masters' by Gary Zukav, and was fairly intrigued by its implications. Can anyone tell me of what the theorem actually consists? Zukav never actually put the mathematics forward, but I wanted to see if anyone could tell me what...
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