We demonstrate that secure quantum key distribution systems based on continuous variables implementations can operate beyond the apparent 3 dB loss limit that is implied by the beam splitting attack . The loss limit was established for standard minimum uncertainty states such as coherent states. We show that by an appropriate postselection mechanism we can enter a region where Eve's knowledge falls behind the information shared between Alice and Bob even in the presence of substantial losses.
@article{arxiv.quant-ph/0204064,
title = {Continuous Variable Quantum Cryptography - beating the 3 dB loss limit},
author = {Ch. Silberhorn and T. C. Ralph and N. Lütkenhaus and G. Leuchs},
journal= {arXiv preprint arXiv:quant-ph/0204064},
year = {2009}
}