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). Can someone think of a reason why this wouldn't necessarily be so?
Cheers, Bob Hettinga
- alex