一种基于平衡零差探测技术的平均光子数测量方法

An average photon number measurement scheme based on balanced homodyne detection

针对连续变量量子密钥分发系统实用化进程中对系统核心参数的规范标定需求,本文提出了一种基于平衡零差探测技术的平均光子数测量方法,即利用平衡零差探测基本结构,在本振臂添加一个电光相位调制器.不同于通过计算相位漂移值进行被动相位补偿的方式,本方法主动地对相位调制器加载[0,2π]的均匀随机相位以避免相位漂移对测量结果的影响.仿真及实验验证了平衡零差探测器输出信号服从带有两个峰值的驼峰分布,且探测输出信号方差与待测光脉冲平均光子数呈线性关系.采用该方案实现的平均光子数测量精度为0.1个光子/脉冲,测量范围达23 dB.优化选择探测器性能和数据采集工具的采样精度和量程,可实现满足测量要求的平均光子数和脉冲消光比测量,为连续变量量子密钥分发系统的关键参数标准化提供了一种可行方案.

Quantum key distribution(QKD)has become an alternative technology defensing the security threat resulting from quantum computing.Owing to its superiority in coexistence with optical infrastructures and cost-effective,continuous variable QKD(CV-QKD)is widely studied and developed towards the practical application stage.The standardized measurement of critical parameters of the system should be studied urgently.[0,2π]In this work we propose a scheme based on balanced homodyne detection with phase-randomized local oscillator to realize the average photon number measurement.By controlling local oscillator phase positively,which obeys uniform distribution,a linear relationship between average photon numbers and the variance of detector output can be obtained in simulation and experiment.With high-accuracy(~0.1)photons/pulse and large range~23 dB,this average photon number measurement scheme provides a great reference to evaluating the critical parameters of CV-QKD system in the practical process.