Cancer. p53 Guardian of the Genome

Abstract

be set up again; if the test is positive the remaining unrevealed bits form the key. In practice, Bennett suggests using dim coherent light pulses differing in phase relative to an accompanying bright reference pulse. Pairs of such dim pulses are non-orthogonal and can be both produced and detected in Mach-Zehnder interferometers (see figure). This system, unlike some earlier quantum cryptosystems , has one big advantage namely , it does not employ photon polarization to encode the key. As quantum information cannot be amplified without losing its quantum character , dropping the need to preserve the photon polarization over long distances gives us a chance of providing the basic components for a long-distance key-distributing apparatus. Indeed, with low-attenuation optical fibres (0.17 dB km-I) and new silicon photodetectors, Ben-nett's approach should make it possible to distribute keys over several kilometres rather than the present 30 cm, definitely bringing quantum cryptography into the realm of the plausible. 0 Artur Ekert is in the