Vol. 43, Issue 2, pp. 373-381

Abstract

A novel thermal light based scheme utilizing the second-order coherence is proposed for ultra-high accuracy synchronization of two distant clocks. By using two-photon absorption, which involves an almost simultaneous absorption of two photons within a maximum delay given by the Heisenberg principle, the second-order coherence at a femtosecond scale for a real thermal source has been observed (Boitier F. et al., Nature Physics 5(4), 2009, p. 267). We show that the clock synchronization accuracy can achieve, in principle, a femtosecond range. And the scheme can be realized with currently available technology, at least for a proof of principle.