Abstract

Quantum cryptographic systems employ secret keys exchanged between two parties in the form of a stream of polarisation- or phase-encoded single photons. Under ideal conditions the absolute security of the quantum key is guaranteed by the laws of quantum physics, since any attempt at eavesdropping will introduce gross bit errors which will be quickly detected by the legitimate parties to the key exchange. Secure quantum key distribution (QKD) is currently limited to distances of several tens of kilometres. It has been suggested [1,2] that key distribution over global distances will require the use of free-space optical inter satellite (O-ISL) and ground to satellite links.

© 2000 IEEE