Picosecond-Precise Long-Term Synchronization for Remote Quantum Network Nodes

Entanglement swapping is a critical capability for enabling long-distance quantum networks. Achieving high-visibility swapping requires precise synchronization of remote nodes so that the mean arrival-time difference of incoming photons remains within a few picoseconds. We have demonstrated stable node synchronization with a fixed mean arrival-time drift below 3 ps over 24 hours across both ANL–FNAL and FNAL–FNAL building links. These results provide a robust foundation for entanglement-based quantum communication and networking applications between geographically separated sites.