Quantum Key Distribution in Access Networks

Jing Wang, Zhensheng Jia

Mingxuan Guo, Chen Gong, Peng Huang +2 more

Abstract Continuous-variable quantum key distribution (CVQKD) is a highly promising method for building large-scale quantum networks due to its low cost and high capacity. However, current access networks involve hybrid channels and multiple users, where traditional CVQKD protocols may face limitations in performance. At the same time, as an emerging protocol, quantum key distribution with basis-encoding (BE-QKD) is compatible with traditional CVQKD protocols and has the potential to be applied in CVQKD access networks to provide performance advantages. But the performance of the BE-QKD protocol in current CVQKD access networks has not yet been fully exploited. In this work, we conduct an experimental demonstration of a heterogeneous continuous-variable quantum access network, which is based on the BE-QKD protocol with quadrature phase shift keying (QPSK) modulation and the traditional QPSK-CVQKD protocol. In addition, practical CVQKD access networks may involve different types of transmission links. Therefore, this access network is configured with four users, including two free-space channels and two fiber channels, to verify the feasibility of the proposed heterogeneous quantum access network scheme in a hybrid-channel environment. The experimental results demonstrate that the QPSK-BE-QKD protocol offers potential performance advantages across various channel scenarios in quantum access networks, such as the ability to withstand channel loss and secret key rates. And its compatibility with QPSK-CVQKD is confirmed. The proposed scheme is easy to deploy in existing CVQKD access networks and demonstrates significant performance potential, offering a new implementation paradigm for large-scale access scenarios of CVQKD networks with complex and hybrid channels.

Miralem Mehić, Stefan Raß, Peppino Fazio +1 more

Yundi Huang, Tao Shen, Xiangyu Wang +4 more

Quantum key distribution (QKD) which enables the secure distribution of symmetric keys between two legitimate parties is of great importance in future network security. Access network that connects multiple end-users with one network backbone can be combined with QKD to build security for end-users in a scalable and cost-effective way. Though previous QKD access networks are all implemented in the upstream direction, in this paper, we prove that downstream access network can also be constructed by using continuous-variable (CV) QKD. The security of the CV-QKD downstream access network is analyzed in detail, where we show the security analysis is secure against other parties in the network. The security analysis we proved corresponds to the downstream access network where only passive beamsplitter is sufficient to distribute the quantum signals and no other active controls are demanded. Moreover, standard CV-QKD systems can be directly fitted in the downstream access network, which makes it more applicable for practical implementations. Numerous simulation results are provided to demonstrate the performance of the CV-QKD downstream access network, where up to 64 end-users are shown to be feasible to access the network. Our work provides the security analysis framework for realizing QKD in the downstream access network which will boost the diversity for constructing practical QKD networks.

Nilesh Vyas, Paulo Mendes

Quantum security over long distances with untrusted relays is largely unfounded and is still an open question for active research. Standard Quantum Key Distribution Network (QKDN) architecture demands full trust in QKD relays, which is too restrictive and limits QKDN applications. We investigate secure secret relaying in QKDNs by relaxing the trust assumptions (if not completely) on the relay. We classify QKD relays into Full Access Trust (FAT), Partial Access Trust (PAT), and No Access Trust (NAT) levels, each reflecting the required trust on the key management system for end-to-end communication. We review and propose QKD key management systems based on these trust levels. We propose a new decentralized key management system and review key management within a centralized topology. These different approaches offer various advantages based on QKDN requirements, granting operational flexibility. We believe this work offers a fresh perspective on the challenge of ensuring secure long-range communications in the future.

K. Yoshino