Experimental Demonstration of Passive-Decoy-State Quantum-Key-Distribution with Two Independent Lasers

TL;DR

This paper experimentally demonstrates a passive-decoy-state quantum key distribution protocol using two independent lasers and linear optics, achieving secure key generation over 10 km fiber without active modulation.

Contribution

It presents the first experimental realization of passive-decoy-state QKD with independent lasers and linear optics, expanding practical options for secure quantum communication.

Findings

Achieved secret key rate of 1.5×10⁻⁵ per pulse over 10 km fiber

Demonstrated passive decoy state generation with two independent lasers

Validated theoretical models with experimental data

Abstract

Decoy state method could effectively enhance the performance of quantum key distribution (QKD) with practical phase randomized weak coherent source. Although active modulation of the source intensity is effective and has been implemented in many experiments, passive preparation of decoy states is also an important addition to the family of decoy state QKD protocols. In this paper, following the theory of Curty \emph{et al.} [PRA, 81, 022310 (2010)], we experimentally demonstrate the phase-encoding passive-decoy-state QKD with only linear optical setups and threshold single photon detectors. In our experiment, two homemade independent pulsed lasers, with visibility of Hong-Ou-Mandel interference $0.53(\pm 0.003)$, have been implemented and used to passively generate the different decoy states. Finally, secret key rate $1.5\times 10^{-5}$/pulse is obtained with 10km commercial fiber between Alice and Bob.