The operation of long-distance quantum networks requires photons to be synchronized and must account for length variations of quantum channels. We demonstrate a 200 MHz clock-rate fiber optic-based quantum network using off-the-shelf components combined with custom-made electronics and telecommunication C-band photons. The network is backed by a scalable and fully automated synchronization system with ps-scale timing resolution. Synchronization of the photons is achieved by distributing O-band-wavelength laser pulses between network nodes. Specifically, we distribute photon pairs between three nodes, and measure a reduction of coincidence-to-accidental ratio from 77 to only 42 when the synchronization system is enabled, which permits high-fidelity qubit transmission. Our demonstration sheds light on the role of noise in quantum communication and represents a key step in realizing deployed co-existing classical-quantum networks.
@article{arxiv.2203.03127,
title = {Picosecond synchronization system for quantum networks},
author = {Raju Valivarthi and Lautaro Narváez and Samantha I. Davis and Nikolai Lauk and Cristián Peña and Si Xie and Jason P. Allmaras and Andrew D. Beyer and Boris Korzh and Andrew Mueller and Mandy Rominsky and Matthew Shaw and Emma E. Wollman and Panagiotis Spentzouris and Daniel Oblak and Neil Sinclair and Maria Spiropulu},
journal= {arXiv preprint arXiv:2203.03127},
year = {2023}
}