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The only mystery in QM

  1. Feb 16, 2012 #1
    Feynman said that " [the double slit int. pattern contains] the only mystery in QM"

    was quantum entanglement not established (and bells theorem not postulated) then yet?

    or did Feynman believe that the explanation for the double slit (interference pattern) would also somehow explain quantum entanglement?
  2. jcsd
  3. Feb 16, 2012 #2


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    When did Feynman make this claim? The EPR paradox was published in 1935, and Bell published his results in 1964, but it wasn't until 1976 that this was tested by Lamehi-Rachti and Mittig. See the wikipedia article on EPR paradox for more history.
  4. Feb 16, 2012 #3
    below is one of the (numerous) references to the above quote by Feynman:

  5. Feb 16, 2012 #4
    I don't know where that quote specifically comes from, but I know he also said that all of the mysteries of QM can be found in the double slit experiment. The quote that I remember (I think it is in QM and Path Integrals, but it might be in the Lectures) implies not that the experiment is totally misunderstood, but the student of QM can learn a lot by thinking about all of the implications from it. I don't know if your quote was meant in a similar manner or not.
  6. Feb 16, 2012 #5
    the quote is meant in a similar/same manner.

    so the question is:

    did Feynman then believe that Quantum Entanglement (another mystery of QM) can be found in the double slit experiment?
  7. Feb 16, 2012 #6
    I misunderstood your question.
    The timing is off for him having knowledge of Bell's Theorem (quote prob. dates from 1961-62), and perhaps the specifics of entanglement may not have been something he was specifically talking about, but the non-locality of QM is present in the double slit experiment.
    However, he was addressing Freshmen... so I bet he was just hoping one of the boys in the class would be impressed and set him up with their sister.
  8. Feb 17, 2012 #7
    The essential mystery of quantum mechanics is wave-particle duality. In terms of waves, the wonders of quantum entanglement don't really reveal themselves: the fraction of light that goes through a polarizer is well-described by Malus' law, which is entirely classical. It is only when you put polarization experiments in the context of other experiments which show the particle-like nature of light that Bell-type effects suddenly lead to profound philosophical issues.

    And the double slit experiment certainly deals with this duality.
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