单光子源通常采用基于高斯光束的高度衰减激光脉冲, 假设激光束具有初始高斯时域脉冲波形和TEM01模拉盖尔-高斯空域分布.基于折射率起伏的Rytov近似和修正von Karman谱模型, 研究了大气湍流对星地量子通信单光子捕获概率的影响; 建立了上行信道和下行信道的单光子捕获概率理论模型; 针对低轨卫星-地面站间激光链路, 对单光子捕获概率进行了分析.结果表明: 上行信道的单光子捕获概率强烈依赖于地面折射率结构常数C2n(0), 且随着C2n(0)的增加而减小; 然而, 下行信道的单光子捕获概率并不依赖于C2n(0), 即大气湍流对其没有影响.

Highly attenuated laser pulses based on Gaussian beams are used as single-photon sources. It is assumed that this laser beam has an initial Gaussian temporal pulse shape and a TEM01 mode Laguerre-Gaussian spatial profile. Based on the Rytov approximation and the modified von Karman spectrum model of refractive-index fluctuations, the influence of atmospheric turbulence on a single-photon acquisition probability in satellite-ground quantum communications was studied. Theoretical models of the single-photon acquisition probability in an uplink channel and a downlink channel were established. The single-photon acquisition probability was analyzed for laser links between a ground station and a satellite in a low earth orbit. The results show that, the single-photon acquisition probability in the uplink channel depends strongly on the refractive-index structure parameter at the ground C2n(0) and decreases as C2n(0) increasing. However, in the downlink channel the single-photon acquisition probability does not depend on C2n(0), that is, atmospheric turbulence has little influence on it.