Synchronous frequency comparison beyond the Dick limit based on dual-excitation spectrum in an optical lattice clock

Abstract

We present a synchronous frequency comparison method based on one cold-Atom ensemble by using the dual-excitation spectrum technique, which can simultaneously detect the probabilities of two different clock transitions. We experimentally verify this synchronous frequency comparison method between | m F | = 9 / 2 and | m F | = 7 / 2 in a one-dimensional 87Sr optical lattice clock and the comparison instability is well below the Dick limit. We also extend the dual-excitation spectrum method to shorten the clock feedback cycle by a half in optical lattice clocks and experimentally demonstrate that the interleaved self-comparison instability is 1.4 times lower than that of the traditional operation method.