Experimental Side-Channel-Secure Quantum Key Distribution over 200 km

TL;DR

This paper reports the first long-distance (200 km) side-channel-secure quantum key distribution experiment, achieving high secure key rates and demonstrating practical, secure quantum communication over unprecedented distances.

Contribution

It experimentally implements a practical SCS-QKD protocol over 200 km using an imperfect source and finite-key analysis, setting a new distance record.

Findings

Achieved secure key rates of 18.31 kbps at 100 km, 2.55 kbps at 150 km, and 196.03 bps at 200 km.

Extended the transmission distance for SCS-QKD to 200 km, surpassing previous limits.

Demonstrated the feasibility of high-speed, long-distance, secure quantum communication.

Abstract

Quantum key distribution (QKD) enables two remote parties to share encryption keys with information-theoretic security guaranteed by physical laws. Side-channel-secure QKD (SCS-QKD) has attracted considerable attention because it simultaneously removes source and detector side-channel vulnerabilities. Although a recent experiment demonstrated SCS-QKD over 50 km, practical implementation remains challenging due to imperfect vacuum preparation and finite-key constraints under coherent attacks. Here, following the theoretical framework of Jiang et al. [Phys. Rev. Res. 6, 013266 (2024)], we experimentally implement a practical SCS-QKD protocol using an imperfect whole-space source and rigorous finite-key analysis. Benefiting from a stable GHz-level system operating at 1.25 GHz, we extend the transmission distance to 200 km and achieve high secure key rates of 18.31 kbps, 2.55 kbps, and 196.03 bps at 100 km, 150 km, and 200 km, respectively. Our results establish a new distance record for SCS-QKD and demonstrate the feasibility of high-speed, long-distance, and practically secure quantum key distribution.