From: hal@finney.org
Date: Mon Jan 14 2002 - 12:57:55 MST
Scerir writes:
> Raymond Chiao and Paul Kwiat (among the very best in the field)
> performed experiments with a couple of entangled photons (PDC
> generated). One member of the pair (the idler) is sent to a filter
> and to a photomultipier. The other member (the signal) is sent to
> an interferometer (Michelson type). Now, in order to conserve
> total energy and to fullfill the uncertainty (time, energy) relations,
> they find that the visibility of the signal photon fringes depends
> on the bandwith of the filter through which just the idler photon
> goes. Thus the width of the collapsing signal photon wave packet
> depends on that (remote, and well separated) filter.
I don't think this description can be correct. You make it sound like
changing the filter over here causes instantaneous observable changes
in the interference fringes over there. Clearly this would contradict
relativity, which you say the experiment does not do. Presumably there
is some need to bring the photons (or at least information about them)
together after the experiment in order to observe the changes in the
interference fringes. In that case there is an ordinary causal link
between changing the filter and the observed changes, due to particles
which had passed through the filter.
Hal
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