Research progress of Al$^{+}$ ion optical frequency standard based on quantum logic technique

Abstract

Optical atomic clocks have many applications in the definition of the time and the length, measurement of fundamental constants and their potential variations with time, testing of relativity, very long baseline interferometry, geodesy, and global navigation satellite systems. An optical clock consists of three parts: ultra-stable laser, frequency comb and trapped ions or atoms. The accuracy of optical atomic clocks can be affected by Doppler shift, Zeeman shift, Stark shift, collision shift, blackbody radiation (BBR) shift, etc. The BBR shift is very difficult to be characterized and controlled. Among all optical atomic clocks under current development, Al$^+$ optical clock has the smallest BBR shift at a level of $4.0\times10^{-19}$, therefore the Al$^+$ is a promising ion for high-accuracy optical frequency standard. In this article we give a review on the three parts of optical frequency standards, the basic working principle of Al$^+$ ion optical frequency standard based on quantum logic technique, and research progress of an Al$^+$ optical clock under development at Huazhong University of Science and Technology.