Quantum key distribution with triggering parametric down conversion sources

TL;DR

This paper generalizes decoy state methods for quantum key distribution using parametric down-conversion sources, demonstrating near-optimal key rates with practical detectors through simulation.

Contribution

It introduces a generalized passive decoy state approach applicable to various detector types, unifies existing protocols, and compares their performance via simulation.

Findings

AYKI protocol achieves near-theoretical key rates.

Photon-number resolving detectors offer limited performance improvement.

Generalized method applies to other triggered single photon source setups.

Abstract

Parametric down-conversion (PDC) sources can be used for quantum key distribution (QKD). One can use a PDC source as a triggered single photon source. Recently, there are various 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 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 infinite decoy 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 the QKD with PDC sources, we emphasize that it can also be applied to other QKD setups with triggered single photon sources.