Passive scheme with a photon-number-resolving detector for monitoring the untrusted source in a plug-and-play quantum-key-distribution system

TL;DR

This paper introduces a passive photon-number-resolving detector scheme to verify untrusted source statistics in quantum key distribution, analyzing practical issues and demonstrating feasibility with current technology.

Contribution

It proposes a novel passive PNR detector scheme for source verification in QKD, including practical implementation details and analysis of real-world issues.

Findings

Efficient operation with over 10^8 pulses sent from Alice to Bob.

PNR detector with dark count rate below 0.5 counts/pulse is feasible.

Practical realization using a variable attenuator and threshold detector is proposed.

Abstract

A passive scheme with a beam splitter and a photon-number-resolving (PNR) detector is proposed to verify the photon statistics of an untrusted source in a plug-and-play quantum-key-distribution system by applying a three-intensity decoy-state protocol. The practical issues due to statistical fluctuation and detection noise are analyzed. The simulation results show that the scheme can work efficiently when the total number of optical pulses sent from Alice to Bob is above 10^8, and the dark count rate of the PNR detector is below 0.5 counts/pulse, which is realizable with current techniques. Furthermore, we propose a practical realization of the PNR detector with a variable optical attenuator combined with a threshold detector.