paper

Beating the PNS attack in practical quantum cryptography

arXiv:quant-ph/0410075 · doi:10.1103/PhysRevLett.94.230503

Abstract

In practical quantum key distribution, weak coherent state is often used and the channel transmittance can be very small therefore the protocol could be totally insecure under the photon-number-splitting attack. We propose an efficient method to verify the upper bound of the fraction of counts caused by multi-photon pluses transmitted from Alice to Bob, given whatever type of Eve's action. The protocol simply uses two coherent states for the signal pulses and vacuum for decoy pulse. Our verified upper bound is sufficiently tight for QKD with very lossy channel, in both asymptotic case and non-asymptotic case. The coherent states with mean photon number from 0.2 to 0.5 can be used in practical quantum cryptography. We show that so far our protocol is the decoy-state protocol that really works for currently existing set-ups.

So far this is the unique decoy-state protocol which really works efficiently in practice. Prior art results are commented in both main context and the Appendix

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