paper

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

arXiv:2002.03476 · doi:10.1103/PhysRevA.103.012605

Abstract

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.

arXiv comment15 pages, 3 figures

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