Abstract
Parametric down-conversion (PDC) sources can be used as triggered single photon sources in quantum key distribution (QKD). Recently, there have been several practical proposals of the decoy state QKD with triggering PDC sources. In this paper, we generalize the passive decoy state idea, originally proposed by Mauerer and Silberhorn. The generalized passive decoy state idea can be applied to cases where either threshold detectors or photon-number-resolving detectors are used. The decoy state protocol proposed by Adachi, Yamamoto, Koashi and Imoto (AYKI) can be treated as a special case of the generalized passive decoy state method. By simulating a recent PDC experiment, we compare various practical decoy state protocols with the infinite decoy state protocol and also compare the cases using threshold detectors and photon-number-resolving detectors. Our simulation result shows that with the AYKI protocol, one can achieve a key generation rate that is close to the theoretical limit of an infinite decoy state protocol. Furthermore, our simulation result shows that a photon-number-resolving detector appears to be not very useful for improving QKD performance in this case. Although our analysis is focused on QKD with PDC sources, we emphasize that it can also be applied to QKD setups with other triggered single photon sources.
Highlights
Parametric down-conversion (PDC) sources can be used for quantum key distribution (QKD)
The simulation result shows us that the coherent state QKD with decoy states is able to operate as good as QKD with perfect single photon sources in the sense that the key generation rates given by both setups depend linearly on the channel transmittance [19]
By investigating the optimal photon source intensity, we find that the triggering PDC QKD setup with decoy states is able to achieve a key rate that linearly depends on the channel transmittance, comparing to the quadratic dependence for the case without decoy states
Summary
Quantum key distribution (QKD) [1, 2] allows two legitimate parties, Alice and Bob, to create a random secret key even when the channel is accessible to an eavesdropper, Eve. The simulation result shows us that the coherent state QKD with decoy states is able to operate as good as QKD with perfect single photon sources in the sense that the key generation rates given by both setups depend linearly on the channel transmittance [19]. The generalized passive decoy state idea can be applied to both cases of using threshold detectors and photon-number resolving detectors. The QKD performance of the case with the infinite decoy protocol using threshold detectors is close to the case using a perfect photon-number resolving detector. In Appendix A, we consider the optimal PDC source intensities for the triggering PDC QKD
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