基于信道估计的自适应连续变量量子密钥分发方法

为使连续变量量子密钥分发协议获得稳定的密钥生成率，需要根据信道变化动态调整发送光脉冲的强度.将光纤量子信道看作加性玻色量子高斯信道，给出高斯态通过玻色量子高斯信道仍得到高斯态的证明过程.通过平衡零差检测后，采用最大似然估计法得到了信道参数，进而根据估计的噪声大小自适应调整Alice发送的光脉冲的强度，从而获得稳定的密钥生成率. 关键词： 量子密钥分发 连续变量 玻色量子高斯信道 信道估计

Adaptive continuous variable quantum key distribution based on channel estimation

In order to obtain steady key rate for a continuous variable quantum key distribution system, Alice should adaptively adjust the intensity of optical pulses she sents. In this paper, an optical fiber channel is taken as the additive bosonic quantum Gaussian channel. It is proven that a Gaussian channel transforms Gaussian states into Gaussian states. The maximum-likelihood method is used to estimate the channel parameters after balanced homodyne detection. Then, Alice can change the intensity of optical pulses adaptively according to the estimated noise level, thereby a steady key rate can be obtained.