CPT atom clock, which works on the theory of coherent population trapping, has great advantages of small volume and low power consumption. Theoretically, only CPT clock can realize micromation, such as clocks have the size of a watch and power by button cell. It has great future in long-distance-communication, system timing, large-scale communication network synchronization, military applications. Europe and America have attached great importance to the research of CPT frequency standard. Up to the present day, there are two commercial CPT clocks in USA.

　　After the realization of the first CPT model of China in 2006, team led by professor Si-Hong Gu try to work out a clock for application. Recently, they make important progress in the key technology of CPT clock and achieve obvious improvement of the clock, which has a comparable stability and power consumption with the commercial clock mentioned before. Now their next step is to optimize the design, improve the technology and work out a CPT clock meeting application demand.