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arXiv · 2504.00802

Entanglement-verified time distribution in a metropolitan network

Mohammed K. Alqedra·Samuel Gyger·Katharina D. Zeuner·Thomas Lettner·Mattias Hammar·Gemma Vall Llosera·Val Zwiller
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Abstract

The precise synchronization of distant clocks is a fundamental requirement for a wide range of applications. Here, we experimentally demonstrate a novel approach of quantum clock synchronization utilizing entangled and correlated photon pairs generated by a quantum dot at telecom wavelength. By distributing these entangled photons through a metropolitan fiber network in the Stockholm area and measuring the remote correlations, we achieve a synchronization accuracy of tens of picoseconds by leveraging the tight time correlation between the entangled photons. We show that our synchronization scheme is secure against spoofing attacks by performing a remote quantum state tomography to verify the origin of the entangled photons. We measured a distributed maximum entanglement fidelity of $0.817 \pm 0.040$ to the $|\Phi^+\rangle$ Bell state and a concurrence of $0.660 \pm 0.086$. These results highlight the potential of quantum dot-generated entangled pairs as a shared resource for secure time synchronization and quantum key distribution in real-world quantum networks.

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Mohammed K. Alqedra, Samuel Gyger, Katharina D. Zeuner, Thomas Lettner, Mattias Hammar, Gemma Vall Llosera, Val Zwiller. 2025-04-01. Entanglement-verified time distribution in a metropolitan network. https://doi.org/10.1364/opticaq.571619

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