近日，丹麦技术大学的Tobias Gehring&Adnan A. E. Hajomer&Ivan Derkach及其研究团队，提出了连续变量量子无源光学网络。相关研究成果已于2024年10月16日在国际知名学术期刊《光：科学与应用》上发表。

据悉，为了建立一个可扩展且安全的量子网络，一个关键的里程碑是从基本的点对点量子密钥分发（QKD）系统，向开发旨在最大化网络容量的固有多用户协议迈进。

该研究团队提出一种基于连续变量（CV）系统的量子无源光网络（QPON）协议，特别是利用相干态的正交分量，实现了所有网络用户之间确定性、同时性且高速率的密钥生成。研究人员实现了两种协议，分别对应网络用户的不同信任级别，并在一个拥有8个用户、每个用户接入链路长度为11公里的量子接入网络中，实验验证了密钥生成。

根据对用户信任度的不同假设，研究人员实现了总网络密钥生成速率为1.5和2.1Mbits/s（或在使用有限尺寸信道估计时为0.4和1.0Mbits/s）。该CV-QPON协议展示了将网络容量扩展到高速支持数十个用户的潜力，为建立低成本、高速率且可扩展的安全量子接入网络开辟了新途径，这是迈向量子互联网的重要一步。

附：英文原文

Title: Continuous-variable quantum passive optical network

Author: Hajomer, Adnan A. E., Derkach, Ivan, Filip, Radim, Andersen, Ulrik L., C. Usenko, Vladyslav, Gehring, Tobias

Issue&Volume: 2024-10-16

Abstract: To establish a scalable and secure quantum network, a critical milestone is advancing from basic point-to-point quantum key distribution (QKD) systems to the development of inherently multi-user protocols designed to maximize network capacity. Here, we propose a quantum passive optical network (QPON) protocol based on continuous-variable (CV) systems, particularly the quadrature of the coherent state, which enables deterministic, simultaneous, and high-rate secret key generation among all network users. We implement two protocols with different trust levels assigned to the network users and experimentally demonstrate key generation in a quantum access network with 8 users, each with an 11km span of access link. Depending on the trust assumptions about the users, we reach 1.5 and 2.1Mbits/s of total network key generation (or 0.4 and 1.0Mbits/s with finite-size channels estimation). Demonstrating the potential to expand the network’s capacity to accommodate tens of users at a high rate, our CV-QPON protocols open up new possibilities in establishing low-cost, high-rate, and scalable secure quantum access networks serving as a stepping stone towards a quantum internet.

DOI: 10.1038/s41377-024-01633-9

Source: https://www.nature.com/articles/s41377-024-01633-9