Multiple-Access Quantum Key Distribution Networks

TL;DR

This paper explores multi-user quantum key distribution networks supporting both quantum and classical communications, analyzing multiple access techniques like CDMA and proposing protocols to enhance secret key rates in scalable hybrid optical setups.

Contribution

It introduces a hybrid quantum-classical network architecture with multiple access strategies and a listen-before-send protocol to improve key generation efficiency.

Findings

Optimal CDMA performance at unity code weight

Proposed listen-before-send protocol enhances key rates

Hybrid network setup supports large user bases

Abstract

This paper addresses multi-user quantum key distribution networks, in which any two users can mutually exchange a secret key without trusting any other nodes. The same network also supports conventional classical communications by assigning two different wavelength bands to quantum and classical signals. Time and code division multiple access (CDMA) techniques, within a passive star network, are considered. In the case of CDMA, it turns out that the optimal performance is achieved at a unity code weight. A listen-before-send protocol is then proposed to improve secret key generation rates in this case. Finally, a hybrid setup with wavelength routers and passive optical networks, which can support a large number of users, is considered and analyzed.