-----BEGIN PGP SIGNED MESSAGE----- At 08:04 AM 2/20/96 -0800, jamesd@echeque.com wrote:
At 07:35 PM 2/19/96 -0800, Timothy C. May wrote:
By analogy, it is not clear to me that a simple regeneration mechanism, with no local observer or recording apparatus, will collapse the wave function. Seems to me an experiment may have already been done along these lines: separate fibers producing an interference pattern and then these inline amps added...if the interference pattern remains, as I would expect, then the amps/regenerators did not constitute a "measurement" in QM terms.
An amplification mechanism will usually couple the signal to the vacuum, and introduce vacuum noise. Another way of thinking of vacuum noise is that amplification mixes the state of the signal, with the (unknown) phase of the universe at infinity.
I would think that the action of a optical fiber amplifier is, in a sense, "negative loss," or the inverse of the kind of loss normally found in a fiber cable. Thus, if quantum crypto can be done through a long fiber at all, the fiber amplifier shouldn't negatively affect it. However, if polarization is important (and I know that "polarization maintaining" fibers are available) then I assume that the amplifier would probably also have to be designed to ensure that polarization would also be maintained through the EDFA (Erbium-Doped Fiber Amplifier.) Jim Bell jimbell@pacifier.com -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMSoOwfqHVDBboB2dAQGyawP/TZDei/hk1S3ohFGCz+z8hlLbYuL5Bswo 17UYtM/NyCdKtZ3K/4t2wuGjKwhzUY8iuzi9b1DiKG5pqlsi4rIMz6VqF5V3dIie 5MjDmlCVabYJR5a5DKbWGb/osVsKJfEDskhMcGKtnjMQc3L/Ua9DzkhXhfQ2GWUh u+4hhjL+i5E= =f/Cm -----END PGP SIGNATURE-----