Abstract

Cryptography has, for a long period of time, been regarded as a part of mathematics, with computational difficulty as a safeguard of information. Unfortunately, faster computers and better algorithms have step by step cracked the protection barriers of even the most sophisticated codes. The quest for unbreakable cryptosystems had to venture outside mathematics, and surprisingly, towards quantum physics. The first unbreakable quantum code was proposed in 1984 by Charles Bennett from IBM Research Laboratory and Gilles Brassard from the University of Montreal^[1], but only in 1990 was it possible to set up an experimental realisation of their cryptosystem.^[2] Further modifications and an alternative cryptosystem have been subsequently proposed by Artur Ekert of Oxford University^[3], and the related experimental work has been undertaken in Britain by John Rarity and Paul Tapster of DRA in Malvern. It seems that this is only the beginning of a fascinating exploration of the links between the quantum world and information and communication theory.

© 1992 IQEC