Proving the unconditional security of a quantum key distribution (QKD) scheme is a highly challenging task as one needs to determine the most efficient attack compatible with experimental data. This task is even more demanding for continuous-variable QKD as the Hilbert space where the protocol is described is infinite dimensional. A very natural way to address this problem is to make an extensive use of the symmetries of the protocols. In this article, we investigate a symmetry in phase space that is particularly relevant to continuous-variable QKD, and explore the way towards a new quantum de Finetti theorem that would exploit this symmetry and provide a powerful tool to assess the security of continuous-variable protocols.
@article{arxiv.0907.3696,
title = {Security of continuous-variable QKD: exploiting symmetries in phase space},
author = {Anthony Leverrier and Evgueni Karpov and Philippe Grangier and Nicolas J. Cerf},
journal= {arXiv preprint arXiv:0907.3696},
year = {2010}
}