基于拉盖尔-高斯光束的单光子捕获概率研究

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.

Study on Single-photon Acquisition Probability Based on Laguerre-Gaussian Beams

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.