Demonstration of multiparty quantum clock synchronization

Abstract

Quantum clock synchronization (QCS) is a kind of method to measure the time difference among spatially separated clocks with the principle of quantum mechanics. The first QCS algorithm proposed by Chuang and Jozsa is merely based on two parties, which is further extended and generalized to multiparty situation by Krco and Paul. They present a multiparty QCS protocol based upon W-state, utilizing shared prior entanglement and broadcasting the classical information to synchronize spatially separated clocks. Shortly afterward, Ben-Av and Exman came up with an optimized multiparty QCS based on Z-state. In this work, we firstly report the demonstrations of these two multiparty QCS protocols in a four-qubit liquid-state nuclear magnetic resonance system. The experimental results show a great agreement with the theoretical predictions and also prove that Ben-AV’s multiparty QCS algorithm is more accurate than Krco’s.