Progress on the <sup>40</sup>Ca<sup>+</sup> ion optical clock

Progress on the ⁴⁰Ca⁺ ion optical clock

Zhang Baolin^{1, 2, 3}, Huang Yao^{1, 2}, Zhang Huaqing^{1, 2, 3}, Hao Yanmei^{1, 2, 3}, Zeng Mengyan^{1, 2, 5}, Guan Hua^{1, 2, †}, Gao Kelin^{1, 2, 4, ‡}

The pulse sequence for one interrogation cycle. In this experiment, the free evolution time is T_free = 80 ms and the time for one cycle is T_c = 99.6 ms. The fluorescence is collected at D₁ for state detection and at D₂ to verify that the ion has returned to the S state after an 854-nm pulse.