Duality of quantum communication channels and a collective intercept-resend attack on quantum key distribution with differential phase shift

摘要

Quantum key distribution with differential phase shift is the least studied. A collective intercept-resend attack has been considered. Analysis of even this simplest attack is not simple. It has been shown that collective measurements with entangled states do not increase information of an eavesdropper as compared to individual measurements. This result is a consequence of the fundamental properties of quantum communication channels, which are attributed to the duality of quantum ensembles and measurements.