Yu Hao, Sciara Stefania, Chemnitz Mario, Montaut Nicola, Crockett Benjamin, Fischer Bennet, Helsten Robin, Wetzel Benjamin, Goebel Thorsten A, Krämer Ria G, Little Brent E, Chu Sai T, Nolte Stefan, Wang Zhiming, Azaña José, Munro William J, Moss David J, Morandotti Roberto
Institut national de la recherche scientifique-Centre Énergie Matériaux Télécommunications, Varennes, QC, Canada.
Shimmer Center, Tianfu Jiangxi Laboratory, Chengdu, China.
Nat Commun. 2025 Jan 2;16(1):171. doi: 10.1038/s41467-024-55345-0.
High-dimensional photon states (qudits) are pivotal to enhance the information capacity, noise robustness, and data rates of quantum communications. Time-bin entangled qudits are promising candidates for implementing high-dimensional quantum communications over optical fiber networks with processing rates approaching those of classical telecommunications. However, their use is hindered by phase instability, timing inaccuracy, and low scalability of interferometric schemes needed for time-bin processing. As well, increasing the number of time bins per photon state typically requires decreasing the repetition rate of the system, affecting in turn the effective qudit rates. Here, we demonstrate a fiber-pigtailed, integrated photonic platform enabling the generation and processing of picosecond-spaced time-bin entangled qudits in the telecommunication C band via an on-chip interferometry system. We experimentally demonstrate the Bennett-Brassard-Mermin 1992 quantum key distribution protocol with time-bin entangled qudits and extend it over a 60 km-long optical fiber link, by showing dimensionality scaling without sacrificing the repetition rate. Our approach enables the manipulation of time-bin entangled qudits at processing speeds typical of standard telecommunications (10 s of GHz) with high quantum information capacity per single frequency channel, representing an important step towards an efficient implementation of high-data rate quantum communications in standard, multi-user optical fiber networks.
高维光子态（qudits）对于增强量子通信的信息容量、噪声鲁棒性和数据速率至关重要。时间-bin纠缠qudits是在光纤网络上实现高维量子通信的有前途的候选方案，其处理速率接近经典电信的速率。然而，它们的使用受到时间-bin处理所需干涉测量方案的相位不稳定性、定时不准确和低可扩展性的阻碍。此外，增加每个光子态的时间-bin数量通常需要降低系统的重复率，这反过来又会影响有效的qudit速率。在这里，我们展示了一个光纤尾纤集成光子平台，通过片上干涉测量系统在电信C波段生成和处理皮秒间隔的时间-bin纠缠qudits。我们通过实验证明了使用时间-bin纠缠qudits的Bennett-Brassard-Mermin 1992量子密钥分发协议，并将其扩展到60公里长的光纤链路，展示了在不牺牲重复率的情况下的维度缩放。我们的方法能够以标准电信典型的处理速度（几十GHz）操纵时间-bin纠缠qudits，每个单频通道具有高量子信息容量，这代表了在标准多用户光纤网络中高效实现高数据速率量子通信的重要一步。
