Recent progress on quantum frequency standards at BIRMM

Abstract

Quantum frequency standards are crucial for time measurement, satellite navigation, telecommunication, and other essential applications. Beijing Institute of Radio Metrology and Measurement (BIRMM) has been working on quantum frequency standards and their applications for tens of years. This paper introduces the latest progress on quantum frequency standards at BIRMM, including a calcium optical clock, an active hydrogen maser, and a mercury ion microwave clock. Based on the 1S0-3P1 transition of calcium atoms, a transportable optical clock prototype is built with a stability of 8 × 10–15 at 1 s. A compact active hydrogen maser has been developed for the Chinese space station. It will be used for scientific research such as examining Einstein’s theory of general relativity and has just been lunched. The preliminary frequency stability of the maser is 1.27 × 10–15 at 10000 s. Additionally, a prototype mercury ion microwave clock is developed using the hyperfine transition between 62S1/2, F = 0 and 62S1/2, F = 1. The trapped Hg+ ions are pumped by mercury discharge lamps and cooled by Helium gas. The measured clock transition linewidth is about 1 Hz, and frequency stability of 4 × 10–13 at 1 s and 4 × 10–14 at 1000 s is achieved.