近日，德国汉诺威莱布尼茨大学的Michael Kues及其研究团队取得一项新进展。经过不懈努力，他们在可重构频率复用网络中实现基于频率箱编码的纠缠量子密钥分发。相关研究成果已于2025年1月16日在国际知名学术期刊《光：科学与应用》上发表。

本文首次展示了基于频率箱编码的纠缠量子密钥分发以及利用频率箱编码实现的可重构纠缠分发。具体而言，研究人员展示了一种新型的可扩展频率箱基分析器模块，该模块允许进行被动的随机基选择，这是量子协议中的关键步骤。重要的是，它为每个用户配备了单个探测器，而不是四个探测器，从而极大地减少了资源开销，降低了暗计数的影响、探测器侧信道攻击的脆弱性以及探测器的失衡问题，进而提高了安全性。

该研究的方法提供了自适应的频率复用能力，可以在不增加硬件开销的情况下增加信道数量，从而提高秘密密钥速率并实现可重构的多用户操作。从长远来看，这一方法能够在不同的网络拓扑结构中实现多个用户之间的动态资源最小化量子密钥分发，并有助于大规模量子网络的扩展。

据悉，大规模量子网络需要采用动态且资源高效的解决方案，以降低系统复杂性，同时保持安全性和性能，从而支持在远距离范围内不断增长的用户数量。目前的时间箱、偏振和轨道角动量等编码方案存在缺乏可重构性的问题，因此面临可扩展性挑战。

附：英文原文

Title: Frequency-bin-encoded entanglement-based quantum key distribution in a reconfigurable frequency-multiplexed network

Author: Khodadad Kashi, Anahita, Kues, Michael

Issue&Volume: 2025-01-16

Abstract: Large-scale quantum networks require dynamic and resource-efficient solutions to reduce system complexity with maintained security and performance to support growing number of users over large distances. Current encoding schemes including time-bin, polarization, and orbital angular momentum, suffer from the lack of reconfigurability and thus scalability issues. Here, we demonstrate the first-time implementation of frequency-bin-encoded entanglement-based quantum key distribution and a reconfigurable distribution of entanglement using frequency-bin encoding. Specifically, we demonstrate a novel scalable frequency-bin basis analyzer module that allows for a passive random basis selection as a crucial step in quantum protocols, and importantly equips each user with a single detector rather than four detectors. This minimizes massively the resource overhead, reduces the dark count contribution, vulnerability to detector side-channel attacks, and the detector imbalance, hence providing an enhanced security. Our approach offers an adaptive frequency-multiplexing capability to increase the number of channels without hardware overhead, enabling increased secret key rate and reconfigurable multi-user operations. In perspective, our approach enables dynamic resource-minimized quantum key distribution among multiple users across diverse network topologies, and facilitates scalability to large-scale quantum networks.

DOI: 10.1038/s41377-024-01696-8

Source: https://www.nature.com/articles/s41377-024-01696-8