Quantum clock synchronization protocol based on microwave-optical entanglement

The cavity electro-opto-mechanical converter serves as a meticulously designed platform where hybrid entanglement, including microwave-optical entanglement, can be efficiently prepared. Leveraging microwave-optical entanglement, we propose a quantum synchronization protocol in this paper. This protocol utilizes the second-order coherence function of entanglement signals to determine the propagation time interval and time offset between two parties. Our results demonstrate that the entanglement feature is well-preserved throughout the entire process. Despite the transformation from microwave photodetection to convenient optical photodetection, the transmission superiority of microwaves in free-space is preserved. Under experimentally accessible parameter settings, we achieve a high synchronization precision of Δ τ =±2.704ps. It is theoretically proven that our quantum synchronization protocol holds promise as a viable candidate for future navigation synchronization systems.