Picosecond Synchronization of Photon Pairs through a Fiber Link between Fermilab and Argonne National Laboratories

TL;DR

This paper demonstrates a three-node quantum network over 118 km of fiber, achieving picosecond synchronization of photon pairs using optical clock distribution, suitable for quantum communication despite some noise effects.

Contribution

It presents the first implementation of picosecond synchronization of photon pairs over a fiber link between major research labs for quantum networking.

Findings

Achieved synchronization with picosecond resolution over 118 km fiber link.

Successfully directed photon pairs to multiple nodes using telecommunication switches.

Maintained a CAR suitable for quantum network applications despite Raman scattering effects.

Abstract

We demonstrate a three-node quantum network for C-band photon pairs using 2 pairs of 59 km of deployed fiber between Fermi and Argonne National Laboratories. The C-band pairs are directed to nodes using a standard telecommunication switch and synchronized to picosecond-scale timing resolution using a coexisting O- or L-band optical clock distribution system. We measure a reduction of coincidence-to-accidental ratio (CAR) of the C-band pairs from 51 $\pm$ 2 to 5.3 $\pm$ 0.4 due to Raman scattering of the O-band clock pulses. Despite this reduction, the CAR is nevertheless suitable for quantum networks.