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±0.040 to the ∣Φ+⟩ Bell state and a concurrence of 0.660±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.
@article{arxiv.2504.00802,
title = {Entanglement-verified time distribution in a metropolitan network},
author = {Mohammed K. Alqedra and Samuel Gyger and Katharina D. Zeuner and Thomas Lettner and Mattias Hammar and Gemma Vall Llosera and Val Zwiller},
journal= {arXiv preprint arXiv:2504.00802},
year = {2026}
}