基于温度变化的相位QKD系统误码率分析

Bit error rate analysis of phase coded quantum key distribution system based on temperature change

基于量子力学基本特性的量子密钥分发系统在经典传输上采用一次一密的加密方式,在理论上具有绝对安全性,但由于系统光学器件不完善等问题,导致量子密钥分发系统存在一定误码。根据盖革模式下的单光子探测器性能,研究温度对量子密钥分发系统暗计数概率以及误码率的影响。首先,在中国寒带地区搭建了基于相位编码的32 km实际远程量子密钥分发系统,全年对该系统进行实际测试与参数采集;其次,引入单光子探测效率和暗计数概率,根据诱骗态QKD协议的原理和单光子探测器的工作模式给出误码率和探测器性能参数的一般理论公式;最后,系统分析单光子探测器的性能对实际远程点对点相位编码的诱骗态QKD系统的影响。研究结果表明:在基于相位编码诱骗态量子密钥分发系统中,影响误码率的主要因素为暗计数概率,调控环境温度能够改变系统暗计数概率,进而影响系统误码率。实验结果与理论分析结果相一致,即温度升高,误码率增大。而在实际工作环境中,系统误码率对于小范围区间内的温度变化表现得并不敏感。

Based on the basic characteristics of quantum mechanics,quantum key distribution system adopts a onetime encryption method in the classical transmission,which has absolute security in theory.However,due to the imperfect optical devices of the system,there are certain errors in the quantum key distribution system.According to the performance of single photon detector in Geiger mode,the influence of temperature on dark count probability and bit error rate of quantum key distribution system was studied.Firstly,32 km practical remote quantum key distribution system based on phase coding was built in the cold region of China,the system was tested and parameters were collected throughout the whole year.Secondly,single-photon detection efficiency and dark count probability were introduced.According to the principle of decoy state QKD protocol and working mode of single-photon detector,the general theoretical formulas of error rate and detector performance parameters were given.Finally,the influence of single photon detector performance on the actual remote point-to-point phase coded decoy state QKD system was systematically analyzed.The results show that in the phase-coded decoy quantum key distribution system,the main factor affecting bit error rate is the dark count probability,and the dark count probability of the system can be changed by adjusting ambient temperature,thereby affecting the bit error rate of the system.The experimental results are consistent with theoretical analysis results,that is,the error rate increases with the increase of temperature.However,in the actual working environment,the system error rate is not sensitive to temperature change in small range.