<title>Quantum cryptography for secret key generation using frequency-division long-distance interferometry</title>

Abstract

A realistic quantum cryptographic system must function in the presence of noise and channel loss inevitable in any practical transmission. We examine the effects of these channel limitations on the security and throughput of a class of quantum cryptographic protocols known as four-state, or BB84. Provable unconditional security against eavesdropping, which is the principal feature of quantum cryptography, can be achieved despite minor channel defects, albeit at a reduced transmission throughput. We present a semi-empirical relation between the fully-secure throughput and the loss and noise levels in the channel. According to this relation, a particular implementation of BB84, based on the frequency-division multiplexing scheme and utilizing commercially available detectors, can reach throughputs as high as 104 - 105 secure bits per second over a practical channel of reasonable quality.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.