Progress towards chip-scale atomic clock in Peking University

In this papar we reported our progress toward chip-scale atomic clock (CPT) based on the ⁸⁷Rb coherent population trapping (CPT) transition. During last year, we did great work in improving the performance of our CSAC, especially in frequency drift and long-term frequency stability. It is a remarkable achievement that the amplitude of the drift is around 7.0×10^-12/day and long-term stability is around 6.7×10^-12 at 10⁵s.