星地量子密钥分配中单光子捕获理论分析

基于TEM10模拉盖尔-高斯光束,推导了自由空间量子密钥分配的单光子捕获概率表达式,分析了低轨卫星-地面站间链路的单光子捕获问题。结果表明,采用TEM10模拉盖尔-高斯型高度衰减激光脉冲作为单光子源,单光子捕获采用前驱波参考脉冲设置时间窗口的方法,可使得卫星上接收机以最大概率捕获光子。单光子捕获概率一般在10-1~10-3量级。与基模高斯光束相比,采用TEM10模拉盖尔-高斯光束的优点是,不会由于卫星运动而产生单光子捕获概率的损耗。通过考虑大气湍流的影响,对单光子捕获概率的表达式进行了修正。

Theoretical analysis of single-photon acquisition in satellite-to-ground quantum key distribution

The expressions of single-photon acquisition probability are deduced from TEM10 mode Laguerre-Gaussian beams. Single-photon acquisition is analyzed for the links between a ground station and a satellite in a low earth orbit. The results show that single-photon can be acquired by the receiver on the satellite at the maximum probability if highly attenuated laser pulses based on TEM10 mode Laguerre-Gaussian beams are used as single-photon sources and a bright precursor reference pulse can be used to set a short time window. Single-photon acquisition probability is normal on the order of 10-1~10-3. In comparison with the fundamental-mode Gaussian beam, the TEM10 mode Laguerre- Gaussian beams have an advantage because the losses of single-photon acquisition probability can not be caused by the satellite movement. Atmospheric turbulence is considered and the expressions of single- photon acquisition probability are modified.