A cost-efficient quantum access network with qubit-based synchronization

TL;DR

This paper introduces a cost-efficient quantum access network that uses qubit-based synchronization, removing the need for extra hardware and enabling scalable multi-user quantum key distribution over fiber networks.

Contribution

It proposes a novel qubit-based synchronization method for QANs, reducing hardware costs and demonstrating practical implementation with multiple users and favorable key rates.

Findings

Achieved secure key rates of 53.84 kbps and 71.90 kbps over 50 km fiber for two users.

Simulated support for a 64-user network with key rates up to 1070 bps.

Validated the scheme's robustness under cross-talk and loss conditions.

Abstract

Quantum Key Distribution (QKD) is a physical layer encryption technique that enables two distant parties to exchange secure keys with information-theoretic security. In the last two decades, QKD has transitioned from laboratory research to real-world applications, including multi-user quantum access networks (QANs). This network structure allows users to share a single-photon detector at a network node through time-division multiplexing, thereby significantly reducing the network cost. However, current QAN implementations require additional hardware for auxiliary tasks such as time synchronization. To address this issue, we propose a cost-efficient QAN that uses qubit-based synchronization. In this approach, the transmitted qubits facilitate time synchronization, eliminating the need for additional synchronization hardware. We tested our scheme by implementing a network for two users and successfully achieved average secure key rates of $53.84$ kbps and $71.90$ kbps for each user over a 50-km commercial fiber spool. In addition, we investigated the capacity of the access network under cross-talk and loss conditions. The simulation results demonstrate that this scheme can support a QAN with 64 users with key rates up to 1070~bps. Our work provides a feasible and cost-effective way to implement a multi-user QKD network, further promoting the widespread application of QKD.