近日，太原理工大学贺衎团队研究了非凸纠缠单调确定连续变量量子网络中纠缠分布的特征长度。2025年4月24日出版的《物理评论A》杂志发表了这项成果。

量子网络（QN）有望在不久的将来通过长距离分布纠缠态来提高各种量子技术的性能。实现这一目标的第一步是开发新的纠缠度量，这些度量在大规模上既具有信息性，又具有计算可处理性。虽然离散变量（DV）系统存在许多这样的纠缠度量，但缺乏对实验优选的连续变量（CV）系统的全面探索。

研究组引入了一类CV纠缠度量，其中他们识别了一种非凸纠缠单调性——比率负性，它具有一种简单、可扩展的形式，决定了纯高斯态链上最优纠缠交换的指数衰减。这种特征为利用统计物理工具分析基于交换协议的CV QN开辟了途径。

附：英文原文

Title: Nonconvex entanglement monotone determining the characteristic length of entanglement distribution in continuous-variable quantum networks

Author: Yaqi Zhao, Jinchuan Hou, Kan He, Nicolò Lo Piparo, Xiangyi Meng

Issue&Volume: 2025/04/24

Abstract: Quantum networks (QNs) promise to enhance the performance of various quantum technologies in the near future by distributing entangled states over long distances. The first step towards this is to develop novel entanglement measures that are both informative and computationally tractable at large scales. While numerous such entanglement measures exist for discrete-variable (DV) systems, a comprehensive exploration for experimentally preferred continuous-variable (CV) systems is lacking. Here, we introduce a class of CV entanglement measures, among which we identify a nonconvex entanglement monotone—the ratio negativity, which possesses a simple, scalable form that determines the exponential decay of optimal entanglement swapping on a chain of pure Gaussian states. This characterization opens avenues for leveraging statistical physics tools to analyze swapping-protocol-based CV QNs.

DOI: 10.1103/PhysRevA.111.042429

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.111.042429