-----BEGIN PGP SIGNED MESSAGE----- At 01:18 PM 2/18/96 -0500, Alexandra Griffin wrote:

Bob writes:

...

Does anyone know if the new in-line optical amplifiers (not switches!) have any effect on quantum crypto messages?

Yes, any active devices in your communications path would be unable to function without making some kind of classical measurement on the photons involved (e.g. measuring phase relative to a definite test angle, if phase is what's being modulated), thereby collapsing the wavefunction and spoiling any special properties afforded by being able to send photons down the line without "looking at them." Optical repeaters have to pass your signal through an intermediate electronic stage anyway, since we have no purely optical valve/transistor equivalents (bosons don't interact with each other at all).

I love to be picky about such things. Yes, I think bosons _DO_ interact with each other. Before all you physics nerds flame me, hear me out: Photons, while they have no "rest mass" do indeed "gravitate" (they are energy, recall?). In a reference I can no longer find in my 1970 Encyclopedia Brittanica, it stated that a cubic mile of sunshine "weighs" 1/100,000,000 of a milligram. From another source (or maybe the same one?) it stated that the photon "weight" in a cubic centimeter of volume at the core of a star such as our sun (or at the core of a nuclear explosion) is about 1 gram per cubic centimeter. Thus, presumably photons self-gravitate, and thus, SOME bosons "interact," although admittedly this kind of interaction is a few dozen orders of magnitude lower than what you probably intended when you said "Bosons don't interact with each other at all." Jim Bell jimbell@pacifier.com Klaatu Burada Nikto -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMSeY6fqHVDBboB2dAQG7XwQAoGeWJgkUf2Ton5ptuAgps23RN1YVrdS8 MB0t9DIRrmCqNlFOf8c5b3I9ljxpY0JvEMyWG0LYVqp6+ZYBfBwaSEQ9YGI+uzRJ vDIWg/83sBlHDraNiV5f6VBjZNExgvk2N4j1FIploB0SFOBEH3W7ymVa6Z/IZ6fs kYaIKiXp+ns= =YPqX -----END PGP SIGNATURE-----