Modern optical technology has greatly facilitated the implementation of free-space quantum key distribution. However, the influence of atmosphere on the beam propagation is always unpredictable and could impair the system performance to some extent. It is necessary to develop an efficient model that could describe the beam propagation and receiving. In this paper, a single-photon receiving efficiency model is proposed incorporating the single-photon acquisition probability and channel transmittance based on the Gaussian beam propagation. We also present simulation and experiment of beam-spot size widening through a 0.5 km free-space channel to verify the proposed model. The results show that with the increase of turbulence strengths, the single-photon acquisition probability will degrade more sharply. The single-photon receiving efficiency will decrease with the increment of the ratio between beam centroid deflection and the receiving aperture radius r/a.

中文翻译：

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基于高斯光束传播的实用单光子接收效率模型

现代光学技术极大地促进了自由空间量子密钥分发的实现。然而，大气对光束传播的影响总是不可预测的，并且可能在一定程度上损害系统性能。有必要开发一个可以描述光束传播和接收的有效模型。本文提出了一种基于高斯光束传播的单光子获取概率和通道透过率相结合的单光子接收效率模型。我们还展示了通过 0.5 km 自由空间通道扩大束斑尺寸的模拟和实验，以验证所提出的模型。结果表明，随着湍流强度的增加，单光子捕获概率会急剧下降。r/一种.