At 8:13 PM 2/18/96 -0500, Dave Emery wrote:
Bob writes:
Does anyone know if the new in-line optical amplifiers (not switches!) have any effect on quantum crypto messages?
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).
This is not true. There is now a whole technology of optical amplifiers for fiber communications systems that used Ettrium doped fibers pumped with strong light from a laser at a slightly shorter wavelength. These fiber optical amplifiers have gains in the order of 10-12 db in a section of special doped fiber only about 10 feet long.
I don't think that it matters whether you convert to electronics or amplify with laser techniques. The cryptographic secret is kept in the quantum uncertainity of the state of the (single) photon. Anything that collapses that quantum uncertainity acts as a man-in-the-middle and stops the key/OTP generation. ------------------------------------------------------------------------ Bill Frantz | The CDA means | Periwinkle -- Computer Consulting (408)356-8506 | lost jobs and | 16345 Englewood Ave. frantz@netcom.com | dead teenagers | Los Gatos, CA 95032, USA