标题： 自由空间连续变量量子密钥分发系统中的可组合有限尺寸效应 显示英文标题

标题： Composable finite-size effects in free-space CV-QKD systems

摘要： 自由空间信道为在全球通信网络中建立连续变量量子密钥分发（CV-QKD）提供了可能性。 然而，这些信道中透射率的波动性引入了额外的噪声，这会降低可实现的保密密钥速率。 我们考虑两种经典的后处理策略，即高透射率数据的后选择和数据聚类化，以减少信道的波动引起的噪声。 我们首次在现实有限尺寸条件下利用可组合的安全证明对这些策略进行了研究，以应对集体攻击和独立攻击。 我们还提出了一种高效的参数估计方法，用于估计后选择数据或聚类数据的有效高斯参数。 尽管后选择和聚类化都会减少数据量，从而使得可组合的有限尺寸效应变得更加显著，但我们的结果表明，这些策略仍然能够在面对独立攻击和集体攻击时提高有限尺寸密钥速率，特别是在面对集体攻击时有显著的改进——甚至在某些条件下将协议从不安全状态转变为安全状态。 显示英文摘要

摘要： Free-space channels provide the possibility of establishing continuous-variable quantum key distribution (CV-QKD) in global communication networks. However, the fluctuating nature of transmissivity in these channels introduces an extra noise which reduces the achievable secret key rate. We consider two classical post-processing strategies, post-selection of high-transmissivity data and data clusterization, to reduce the fluctuation-induced noise of the channel. We undertake the first investigation of such strategies utilising a composable security proof in a realistic finite-size regime against both collective and individual attacks. We also present an efficient parameter estimation approach to estimate the effective Gaussian parameters over the post-selected data or the clustered data. Although the composable finite-size effects become more significant with the post-selection and clusterization both reducing the size of the data, our results show that these strategies are still able to enhance the finite-size key rate against both individual and collective attacks with a remarkable improvement against collective attacks--even moving the protocol from an insecure regime to a secure regime under certain conditions.