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arXiv:2505.12102 · IEEE International Conference on Quantum Computing and Engineering (QCE)

Scalable Time-Tagged Data Acquisition for Entanglement Distribution in Quantum Networks

Abderrahim Amlou, Thomas Gerrits, Anouar Rahmouni, Amar Abane, Mheni Merzouki, Ya-Shian Li-Baboud, Ahmed Lbath, Abdella Battou, Oliver Slattery

Published Aug 30, 2025• 0 citations
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Abstract

In distributed quantum applications such as entanglement distribution, precise time synchronization and efficient time-tagged data handling are essential. Traditional systems often suffer from overflow, synchronization drift, and storage inefficiencies. We propose a modular Time Tagging (TT) agent that uses a 1 pulse per second (PPS) signal from White Rabbit (WR) devices to achieve network-wide synchronization, while applying real-time calibration, overflow mitigation, and compression. A live two-lab entanglement distribution experiment validated the system's performance, achieving synchronized coincidence detection at 25,000 counts/sec within a 10 ns window. Data optimization reduced the storage and classical communication bandwidth requirement from 14.32 to 3.80 bytes per tag. The results demonstrate a scalable, accurate, and efficient solution for distributed quantum networks.

DOI
10.1109/qce65121.2025.00127

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Precise time synchronization is a fundamental challenge in distributed quantum systems, with direct implications for secure communication, sensing, and next-generation network technologies. In this study, we present a Field Programmable Gate Array (FPGA)-based implementation of a Time-Correlated Entangled Photons (TCEP) source-based synchronization system, achievingsub-nanosecondaccuracy with timing jitter consistently below 200 ps for a distance up to 20 km. The system leverages the strong temporal correlations inherent in entangled photon pairs to compute synchronization offsets between spatially separated nodes. The design features a modular architecture with optimized kernels for temporal correlation, data aggregation, and normalization, enabling efficient resource utilization and high-throughput performance. Experimental validation demonstrates the FPGA's ability to process photon timestamp data and compute cross-correlation functions significantly faster than traditional CPU-based approaches, achieving execution times in the millisecond range even for large datasets. Our FPGA implementation achieved a consistent$\sim$800 times speedup over CPU, with performance largely unaffected by channel length. Resource utilization analysis highlights the scalability of the design, with the fully integrated system operating at a clock frequency of 397.5 MHz while maintaining efficient use of logic elements, registers, and memory blocks. This hardware-efficient approach provides the timing backbone for next-generation technologies, facilitating advancements in ultra-reliable low-latency communication, distributed quantum computing, quantum-enhanced sensing, navigation, and lays a foundation for forthcoming 6G networks and the quantum internet.
We build a network source of indistinguishable photons, synchronized to an external clock, that could be used as scalable modular unit in an extended quantum network infrastructure. We characterize the indistinguishability and synchronization of this source. The Hong-Ou-Mandel dip shows near unity indistinguishability. Allan deviation analysis shows sub-picosecond jitter when locked to an external clock. The jitter figure is more than 10 times smaller than the pulse duration of 30ps. The source is compatible with many clock recovery systems, including the White Rabbit Precision Time Protocol (WR-PTP). This source enables scalable quantum protocols over multi-node, long-distance optical networks.
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Abstract Photonic quantum technology requires precise, time-resolved identification of photodetection events. In distributed quantum networks with spatially separated and drifting time references, achieving high precision is particularly challenging. Here we build on recent advances of using single-photons for time transfer and employ and quantify a fast postprocessing scheme designed to pulsed single-photon sources. We achieve an average root mean square synchronization jitter of 3.0 ps. The stability is comparable to systems with Rb vapor cell clocks with 19 ps at 1 s integration time, in terms of Allan time deviation. Remarkably, our stability is even better than classical high-precision time transfer, like the White Rabbit protocol, although we use significantly less signal (single-photon level). Our algorithms allow local processing of the data and do not affect the secure key rate. It compensates substantial clock imperfections from crystal oscillators and we foresee great potential for low signal scenarios. The findings are naturally suited to quantum communication networks and provide simultaneous time transfer without adding hardware or modifying the single-photon sources.