Long-distance continuous-variable quantum key distribution using non-Gaussian state-discrimination detection

TL;DR

This paper introduces a long-distance CVQKD protocol using non-Gaussian state-discrimination detection and photon subtraction to extend transmission range, with security analysis confirming feasibility over hundreds of kilometers.

Contribution

It presents a novel CVQKD scheme combining non-Gaussian state-discrimination detection and multiplexing, significantly improving maximum transmission distance and security bounds.

Findings

Maximum transmission distance extended to hundreds of kilometers.

Security bounds are tighter when considering finite-size effects.

The scheme outperforms traditional CVQKD protocols in range and security.

Abstract

We propose a long-distance continuous-variable quantum key distribution (CVQKD) with four-state protocol using non-Gaussian state-discrimination detection. A photon subtraction operation, which is deployed at the transmitter, is used for splitting the signal required for generating the non-Gaussian operation to lengthen the maximum transmission distance of CVQKD. Whereby an improved state-discrimination detector, which can be deemed as an optimized quantum measurement that allows the discrimination of nonorthogonal coherent states beating the standard quantum limit, is applied at the receiver to codetermine the measurement result with conventional coherent detector. By tactfully exploiting multiplexing technique, the resulting signals can be simultaneously transmitted through an untrusted quantum channel, and subsequently sent to the state-discrimination detector and coherent detector respectively. Security analysis shows that the proposed scheme can lengthen the maximum transmission distance up to hundreds of kilometers. Furthermore, by taking finite-size effect and composable security into account we obtain the tightest bound of the secure distance, which is more practical than that obtained in the asymptotic limit.