CAP (Cold Atom and Precision Measurement) group is an active group in the field of cold atom physics and precision measurement. The group was founded by Prof. Yiqiu Wang in 1994, we achieved first cesium MOT (Magneto-optical Trap) of china in 1996, first optical molasses of china in 1997, and first atomic fountain of China in 2000. From 2001, the group was leaded by Prof. Xuzong Chen, and started to the set up the facilities of Bose-Einstein Condensation, the group achieved the Bose-Einstein Condensation in 2004, and first atom laser of china in 2005.
Subsequently, based on the systematical study about the amplification of a weak single, the atomic correlation between lattice sites as well as the modifications of the band structure of the optical lattice by interactions，were measured by the coherent resonant Bragg scattering. By using the coherent manipulation techniques, the atoms in the different bands of optical lattice can be rapid and efficient preparation, where the loading time was shortened by three orders of magnitude, that opens the possibility of studying the rich orbital physics. The width of atomic distribution was greatly reduced to 0.05 one photon recoil momentum, and the critical behavior of the correlation length for a Bose gas near the critical temperature was observed in the whole regime.
We have also built a new system and obtained the all-optical BEC of Rb87, and have loaded it into a 3D optical lattice. Through the strong correlation introduced by the optical lattice, we are doing the research about the quantum simulation of magnetic phase transition. Meanwhile, we are preparing the join with K40, and the research of Bose-Fermi mixture in the optical lattice.
Besides，the CAP focuses on the project of building an experimental platform for cold atom experiments in Chinese space station. The whole experimental platform will be stored in a standard cabinet provided by space program authority in science cabin I which will be launched in 2020. The purpose of the project is to achieve Pico kelvin ultra-low temperature and carry some challenging experiments based on the ultracold atom platform. There are six basic experiments which are planned to implement from 2020 to 2024, and several frontier exploration experiments will be carried from 2025 to 2030. At present, we are working on engineering prototype design of ultracold experimental platform.
The CAP is also involving in the research of optical comb and semiconductor frequency standards as well as novel atomic clocks, and many new achievements have been made. Wherein, the performance of optically pumped small cesium clocks are in the leading of the domestic level, which is gradually getting closer to the international level, and make up for the shortcomings of our country in the area of timing. Besides, many independent research and development technologies including automatic frequency stabilization of semiconductor laser, the miniaturization of femtosecond optical comb etc have been transfered to the Peking University Science Park company: Uniquanta Technology Co., Ltd.