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-   -   Superluminal instantaneous influence (http://www.physicsforums.com/showthread.php?t=457229)

scope Dec16-10 05:51 PM

superluminal instantaneous influence
 
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!

strangerep Dec16-10 06:06 PM

Re: nonlocality
 
Quote:

Quote by scope (Post 3041265)
it is well known that after measurement, there is a superluminal instantaneous influence
(but not really communication) in entanglement.

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

Correlation and causation are very distinct concepts.

scope Dec16-10 06:26 PM

Re: nonlocality
 
anyway, the question is: does the same happen both before and after measurement?

strangerep Dec16-10 06:39 PM

Re: nonlocality
 
Quote:

Quote by scope (Post 3041315)
anyway, the question is: does the same happen both before and after measurement?

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

scope Dec16-10 08:32 PM

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?

strangerep Dec16-10 11:15 PM

Re: nonlocality
 
Quote:

Quote by scope (Post 3041477)
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?

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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