Superluminal instantaneous influence

  1. hi,

    it is well known that after measurement, there is a superluminal instantaneous influence (but not really communication) in entanglement.

    I wonder if such influence also happens everytime before measurement as well?

    i would be very grateful to read your reply!
     
  2. jcsd
  3. strangerep

    strangerep 2,227
    Science Advisor

    Re: nonlocality

    It's not "influence" (which is another term for "causation"), but rather correlation.

    Correlation and causation are very distinct concepts.
     
  4. Re: nonlocality

    anyway, the question is: does the same happen both before and after measurement?
     
  5. strangerep

    strangerep 2,227
    Science Advisor

    Re: nonlocality

    One can't correlate the results of measurements before those measurements
    have been performed, i.e., before the results exist.
     
  6. Re: nonlocality

    ok, and what if, before the measurement, the state of the first particle is modified. would the state of the second particle in entanglement be modified to verify again the correlations?. in other words, does the EPR effect applies even without measurement?
     
  7. strangerep

    strangerep 2,227
    Science Advisor

    Re: nonlocality

    Correlation, expectation values, etc, etc, are concepts that apply to an ensemble.
    But you're trying to think of them in the context of a single instance of an experiment.

    I don't think there's much more I can usefully say here in a few lines except "invest
    in a copy of Ballentine". He discusses all this stuff much better and more comprehensively
    than I could ever do here.
     
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