arXiv:2504.13773 · Optics Express

Picosecond synchronization of mode-locked lasers for metropolitan-scale quantum networks

Cory M. Nunn, Nijil Lal, Ivan A. Burenkov, Ya-Shian Li-Baboud, Paulina S. Kuo, Thomas Gerrits, Sergey V. Polyakov

Published Jun 27, 2025• 1 citation

Abstract

We demonstrate picosecond-level synchronization of two actively mode-locked Ti:Sapphire lasers via the white rabbit precision time protocol (WR-PTP), tested over 120 km of deployed optical fiber. This synchronization capability, in combination with the highly single-mode, transform-limited pulses produced by each laser, enables their use as pump lasers for indistinguishable photon sources at remote locations in a quantum network. Here, the WR-PTP serves as a scalable network synchronization protocol, and its performance is compared to traditional methods of local synchronization. We demonstrate pulse-to-pulse synchronization better than 3 ps and time deviation (TDEV) values below 4 ps for all averaging times up to 10 s. With a designed coherence time of 35 ps for single photon sources utilizing these lasers, the achievable temporal overlap corresponds to 98% Hong-Ou-Mandel (HOM) interference visibility between independent sources.

DOI: 10.1364/oe.565677

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