At 12:35 -0800 14/01/2003, Hal Finney wrote:
>Tim May writes:
>> This arises with quantum measurements of course. Once a measurement is
>> made--path of a photon, for example--all honest observers will report
>> exactly the same thing. There simply is no basis for disputing the
>> past, for Alice to say "I saw the photon travel through the left slit"
>> but for Bob to say "I saw it travel through the right slit."
>
>That's an interesting example, because usually the point of two-slit
>experiments is that there is no "fact of the matter" about which slit
>the particle went through. That's why you get interference from
>the double-slit. What would you say about the past in that case?
>Are there two pasts, one where the particle went through each slit,
>which have now recombined to form the present? Or just one past, where
>the particle managed to go through both slits at once?
An interesting paper related to this question, I think, is:
http://xxx.lanl.gov/abs/quant-ph/0210015
Quantum entanglement with acousto-optic modulators: 2-photon beatings
and Bell experiments with moving beamsplitters
Authors: Andre Stefanov, Hugo Zbinden, Antoine Suarez, Nicolas Gisin
Comments: 14 pages, 16 figures
We present an experiment testing quantum correlations with frequency
shifted photons. We test Bell inequality with 2-photon interferometry where we
replace the beamsplitters by acousto-optic modulators, which are equivalent
to moving beamsplitters. We measure the 2-photon beatings induced by the
frequency shifts, and we propose a cryptographic scheme in relation. Finally,
setting the experiment in a relativistic configuration, we demonstrate that the
quantum correlations are not only independent of the distance but also of the
time ordering between the two single-photon measurements.
Bruno
Received on Wed Jan 15 2003 - 03:57:29 PST