Abstract

A practical quantum key distribution (QKD) system has imperfections, which will contribute to quantum bit error rate (QBER) even in the absence of Eve. One important error source is the noise of the receiver's detector, for example, the dark count probability of a single photon detector (SPD) or the “excess noise” of a homodyne detector. The maximum secure distance of a QKD system is limited by the detector's noise, while the secure key rate is proportional to the operating rate of the detector. An ideal detector should be fast and noiseless. Unfortunately, there is a fundamental trade-off between speed and noise.

© 2007 IEEE