Generating the local oscillator "locally" in continuous-variable quantum key distribution based on coherent detection

TL;DR

This paper introduces a pilot-aided scheme for generating a local oscillator locally in CV-QKD, enhancing security and enabling independent laser sources for more robust quantum communication.

Contribution

It proposes and demonstrates a novel method for local oscillator generation in CV-QKD using independent lasers and a pilot scheme, improving security and application scope.

Findings

Phase noise variance measured at 0.04 rad^2

Reliable coherent detection achieved with independent lasers

Potential for secure key distribution over 25 km fiber

Abstract

Continuous-variable quantum key distribution (CV-QKD) protocols based on coherent detection have been studied extensively in both theory and experiment. In all the existing implementations of CV-QKD, both the quantum signal and the local oscillator (LO) are generated from the same laser and propagate through the insecure quantum channel. This arrangement may open security loopholes and also limit the potential applications of CV-QKD. In this paper, we propose and demonstrate a pilot-aided feedforward data recovery scheme which enables reliable coherent detection using a "locally" generated LO. Using two independent commercial laser sources and a spool of 25 km optical fiber, we construct a coherent communication system. The variance of the phase noise introduced by the proposed scheme is measured to be 0.04 (rad^2), which is small enough to enable secure key distribution. This technology also opens the door for other quantum communication protocols, such as the recently proposed measurement-device-independent (MDI) CV-QKD where independent light sources are employed by different users.