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在自由空间量子密钥分配中,单光子源采用具有泊松分布的高度衰减激光脉冲,量子密码术协议采用BB84和B92协议。通过引入量子信道传输率、单光子捕获概率、测量因子和数据筛选因子,建立了量子误码率理论模型,给出了量子误码率的表达式。对于自由空间量子信道,引起量子误码率的主要因素是光学元件、探测器暗噪声和空间光学环境,并对这些因素进行了分析。针对低轨卫星_地面站间链路,进行了量子误码率的数值仿真研究。结果表明,在低轨卫星_地面站间进行量子密钥分配是可行的,限制自由空间量子密钥分配链路距离的主要因素是探测器暗噪声和空间光学环境。
In free-space quantum key distribution, a single photon source uses a highly attenuated laser pulse with a Poisson distribution, and the quantum cryptography protocol uses the BB84 and B92 protocols. By introducing quantum channel transmission rate, single-photon capture probability, measurement factor and data screening factor, a theoretical model of quantum bit error rate is established, and the expression of quantum error rate is given. For the free-space quantum channel, the main factors that cause the quantum error rate are optical components, dark noise of detectors and space optical environment, and these factors are analyzed. Aiming at the link between LEO satellite and ground station, the numerical simulation of quantum bit error rate is carried out. The results show that it is feasible to distribute quantum key between LEO satellite and ground station. The main factors that limit the distance of quantum key distribution link in free space are dark noise of detector and space optical environment.