Security aspects of quantum key distribution with sub-Poisson light

Abstract

The security of quantum key distribution with sub-Poisson light sources is investigated. It is shown that a quantitative analysis of the security of such sources requires only two measured values, the efficiency and second-order correlation. These two numbers represent figures of merit, which characterize the performance of such light sources. We show that sub-Poisson light sources can offer significant improvements in communication rate over Poisson light in the presence of realistic experimental imperfections. We also investigate the amount of channel loss that can be tolerated for secure communication to be possible, and show that this only depends on the second-order correlation, provided the device efficiency exceeds a critical value. If this critical efficiency is exceeded, an inefficient source can perform as well as an efficient one at sufficiently high channel losses.