Bell's theorem

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Bell's theorem is a no-go theorem famous for drawing an important line in the sand between quantum mechanics (QM) and the world as we know it classically.


  • Bell’s theorem is the most profound discovery of science.
    • Henry P. Stapp, "Bell's Theorem and World Process", Nuovo Cimento, Vol. 29B, No. 2, p. 270 (1975).
  • The gist of Bell's theorem is this: no local model of reality can explain the results of a particular experiment.
    • Nick Herbert Quantum Reality - Beyond The New Physics Chapter 11, The Einstein-Podolsky-Rosen Paradox, p. 199
  • Bell himself managed to devise such a proof which rejects all models of reality possessing the property of "locality". This proof has since become known as Bells theorem. It asserts that no local model of reality can underlie the quantum facts. Bell's theorem says that reality must be non-local.
    • Nick Herbert Quantum Reality - Beyond The New Physics Chapter 12, Bell's Interconnectedness Theorem, p. 212
  • Physicists continue to debate whether Bell's theorem is airtight or not. However, the real question is not whether Bell can prove beyond doubt that reality is non-local, but whether the world is in fact non-local.
    • Nick Herbert Quantum Reality - Beyond The New Physics Chapter 13, The Future Of Quantum Reality, p. 238
  • There's an interesting scientific principle that a wrong answer can be much more stimulating to the field than just sort of finding the answer that's in the back of the book. A wrong result gets people excited. Worried. Obviously, you don't really want that to be happening—it's OK for a theorist to come up with a speculative new theory that gets shot down, but experimentalists are supposed to be very careful and their error limits are supposed to be realistic. Unfortunately, with this experiment, whenever you're looking for a stronger correlation, any kind of systematic error you can imagine typically weakens it and moves it toward the hidden-variable range. It was a hard experiment. In those days, at any rate, with the kind of equipment I had, and ... well, what can I say? I screwed up.
    • Michael Horne (physicist), , as quoted by Louisa Gilder, in The Age of Entanglement, Vintage Books, 2008, p. 286: Quote regarding his wrong experimental results that implied that quantum mechanics yielded the wrong prediction regarding Bell's theorem.

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External links[edit]

Wikipedia has an article about:
  • Bell's Theorem by Abner Shimony (2004) in the Stanford Encyclopedia of Philosophy.