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Mermin (1985) quotes an unnamed physicist as saying:

Anybody who's not bothered by Bell's theorem has to have rocks in his head.

This seemed like a pretty dire indictment, so I decided I had better look once again at this sort of thing in hopes that this time I would become disturbed. I read Mermin (1985), Greenberger (1990), and Mermin (1990). (There is also a well known lecture by Sidney Coleman, "Quantum mechanics in your face," but I'm impatient with videos, so I just gleaned the other three references from one of the slides in his talk.) Most of these are about GHZM experiments, which are advertised as similar to experiments that violate Bell's inequality, but more pedagogically direct -- which renewed my hope of being able to make myself bothered.

The following is what I came away with. Is this wrong?

Local realism seems to me to be more or less the statement that entanglement can't exist. What Bell and GHZM tell us is that we can't avoid entanglement using hidden variable theories.

When people say you should be disturbed by Bell and GHZM, I think what they have in mind is that you should be disturbed by entanglement. The only relevance of Bell and GHZM would be if you had in mind some idea of banishing entanglement using hidden variables.

I do find entanglement disturbing, but I have never seen any particular reason to seek escape in hidden variable theories. Am I guilty of having rocks in my head? Have I misunderstood something crucial?

Related: Why is quantum entanglement considered to be an active link between particles?

References, with handy copyright-violating pdf links

Mermin, "Is the moon really there when nobody looks?," Physics Today, April 1985,

Greenberger, Horne, Shimony, and Zeilinger, "Bell's theorem without inequalities"

Mermin, "Quantum mysteries revisited," Am J Phys 58 (1990) 731

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    You say "I do find entanglement disturbing, but I have never seen any particular reason to seek escape in hidden variable theories." How else would explain the correlations measured in microscopic systems? It seems to me that entanglement and hidden variables are the only two naively possible explanations for the weird non-deterministic (or at least not-obviously-deterministic) behavior of the micro world, so rejecting hidden variables is basically equivalent to accepting entanglement, which you admit is disturbing. – tparker Jan 07 '18 at 23:13
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    @tparker: Finding something disturbing isn't the same as seeking to deny it or explain it away. I find it disturbing that Trump is president of the US, but I don't waste my time denying that he was elected. Hidden variable theories were old and musty before I was born, and nothing interesting has ever come out of them. –  Jan 07 '18 at 23:21
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    Ben, you're a respected poster, but this is really more a discussion question than a straight Q&A thing. I'd suggest you open a chat on this topic, rather than asking as a question. – StephenG - Help Ukraine Jan 07 '18 at 23:22
  • In QFT is the whole business of creation and annihilation of quanta not a spread-out instantaneous effect? Accepted but not understood yet somewhat disturbing. Still entanglement follows naturally from it if I'm right. Just as wave form collapse in QM. Or should one say that these are open questions in physics and that not necessarily anything nonlocal is going on? – Jan Bos Jan 07 '18 at 23:28
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    I don't understand what your question is - would you mind reformulating it? I think you're correct that Mermin's quote basically means "Everyone should be bothered by entanglement." And you admit that you are bothered by entanglement. So what's the problem? – tparker Jan 07 '18 at 23:43
  • Does the unnamed physicist seek escape in hidden variable theories? And are you asking for reasons he might seek such escape because you yourself do not see them? This would make more sense because currently you seem to be asking why the unnamed physicist has a reaction that you yourself also have. And isn't "God doesn't roll dice" pretty much the answer? The conflict between the general maxim to look for "explanation" of every correlation and the special prescription to stop looking in the case of entanglement. – Conifold Jan 08 '18 at 04:50
  • Have you explored what happens when the interactions with these entangled particles occur when the particles are a great distance from one another? There's a lot of effects that must propagate faster than the speed of light. Those can be very bothersome unless properly cornered and then wrapped up with a bow put on them. – Cort Ammon Jan 08 '18 at 05:02
  • Thanks for the links to the papers (copyright notwithstanding -- how much of this new "open access" stuff is retroactive?). –  Jan 08 '18 at 05:33

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I think you're in good shape. This kind of "are you troubled by it" statements are only because our intuition is trained in classical fashion where the phenomenon under consideration doesn't exist. For example, are you troubled by:

  1. The twin paradox?
  2. The probabilistic nature of QM?
  3. Schrodinger's cat?
  4. The speed of light in a vacuum being constant for all observers (i.e. breakdown of Galilean relativity)?

These are all things that would've shocked physicists before the 20th century. Bell's theorem is similar.

Allure
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