Quantum key distribution: theory for application

Quantum key distribution bears the promise to set new standards in secure communication. However, on the way from the theoretical principles to the practical implementation we find many obstacles that need to be taken care of. In this article I show how to obtain a key with a realistic setup such that the security of this key can be proven for an important restricted class of eavesdropping attacks, namely the individual attacks. Received: 15 June 1999 / Published online: 3 November 1999