Discrete-variable quantum key distribution with homodyne detection

TL;DR

This paper introduces a hybrid quantum key distribution protocol combining discrete-variable simplicity with continuous-variable efficiency, featuring practical advantages like no shared phase reference and flexible basis choice, suitable for high-speed metropolitan networks.

Contribution

It proposes a novel hybrid QKD protocol that merges DV and CV advantages, with security proof and practical features for real-world implementation.

Findings

Protocol does not require shared reference phase.

Decoding basis can be chosen after measurement.

Suitable for high-speed metropolitan key distribution.

Abstract

Most quantum key distribution (QKD) protocols can be classified as either a discrete-variable (DV) protocol or continuous-variable (CV) protocol, based on how classical information is being encoded. We propose a protocol that combines the best of both worlds -- the simplicity of quantum state preparation in DV-QKD together with the cost-effective and high-bandwidth of homodyne detectors used in CV-QKD. Our proposed protocol has two highly practical features: (1) it does not require the honest parties to share the same reference phase (as required in CV-QKD) and (2) the selection of decoding basis can be performed after measurement. We also prove the security of the proposed protocol in the asymptotic limit under the assumption of collective attacks. Our simulation suggests that the protocol is suitable for secure and high-speed practical key distribution over metropolitan distances.