Practical decoy state for quantum key distribution

TLDR

Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution. The authors present a general theory of a decoy‑state protocol using two decoy states and one signal state, and also introduce a one‑decoy‑state protocol. They develop a theory for a decoy‑state protocol using two decoy states and one signal state, optimize the intensities of these states, introduce a one‑decoy‑state variant, and estimate that even for distances over 100 km the two‑decoy protocol can be implemented with only a few hours of data. The two‑decoy protocol asymptotically reaches the theoretical limit of general decoy protocols, is highly practical, and can be implemented over distances beyond 100 km with only a few hours of data.

Abstract

Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution. Here, we present a general theory of the decoy state protocol based on only two decoy states and one signal state. We perform optimization on the choice of intensities of the two decoy states and the signal state. Our result shows that a decoy state protocol with only two types of decoy states--the vacuum and a weak decoy state--asymptotically approaches the theoretical limit of the most general type of decoy state protocols (with an infinite number of decoy states). We also present a one-decoy-state protocol. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long distance (larger than 100km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical.