Entanglement generation between remote qubit systems is the central tasks for quantum communication. Future quantum networks will have to be compatible with low-loss telecom bands and operate with large separation between qubit nodes. Single-click heralding schemes can be used to increase entanglement rates at the cost of needing an optically phase-synchronized architecture. In this paper we present such a phase synchronization scheme for a metropolitan quantum network, operating in the low-loss telecom L-band. To overcome various challenges such as communication delays and optical power limitations, the scheme consists of multiple tasks that are individually stabilized. We characterize each task, identify the main noise sources, motivate the design choices and describe the synchronization schemes. The performance of each of the tasks is quantified by a transfer-function measurement that investigates the frequency response and feedback bandwidth. Finally we investigate the resulting optical phase stability of the fully deployed system over a continuous period of 10 hours, reporting a short-term stability standard deviation of $σ \approx 30 °$ and a long-term stability of the average optical phase to within a few degrees. The scheme presented served as a key enabling technology for an NV-center based metropolitan quantum link. This scheme is of interest for other quantum network platforms that benefit from an extendable and telecom compatible phase synchronization solution.
Mediated Transmission of Quantum Synchronization in Star Networks
Renmin University of China（中国人民大学）；School of Physics, Renmin University of China（中国人民大学物理学院）；Key Laboratory of Quantum State Construction and Manipulation (Ministry of Education), Renmin University of China（中国人民大学量子态构建与操控教育部重点实验室）
Quantum entanglement distribution coexisting with high-rate, broadband classical optical communications over a real-world fiber connecting remote, synchronized nodes
Northwestern University（西北大学）；University of Naples Federico II（那不勒斯费德里科二世大学）；Ciena Corporation（西纳公司）
