Influence of background light on quantum bit error rate in satellite-to-ground quantum key distribution

Quantum bit error rate is an important operating parameter in quantum key distribution. As to the satellite-to-ground quantum key distribution, the highly attenuated laser pulses with Poisson distribution are used as single-photon sources. The theoretical model of the quantum bit error rate caused by the background light is established and the expressions of the quantum bit error rate are given. The quantum bit error rate is analyzed in the numerical simulation for the laser links between a ground station and a 300km altitude satellite in a low earth orbit. The study shows that the background light is one of the main factors that limit the link distance for free-space quantum key distribution, and that it is feasible to implement quantum key distribution between a ground station and a satellite in a low earth orbit. In daylight, the quantum bit error rate is on the order of 10^-3∼10^-2, at night, 10^-4 during a full moon and lO^-lO''5 during a new moon.