Jie Zhang(张洁), Ke Deng(邓科), Jun Luo(罗俊), Ze-Huang Lu(陆泽晃)
MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics,
Huazhong University of Science and Technology, Wuhan 430074
(Received 19 January 2017)
The Al+ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of Al+ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al+ traps are utilized. The first trap is used to trap a large number of Al+ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al+ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167nm laser. The expected clock laser stability can reach 9.0 × 10−17/√τ. For the second trap, in addition to 167nm laser Doppler cooling, a second stage pulsed 234nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1 × 10−18. The proposed Al+ ion optical clock has the potential to become the most accurate and stable optical clock.
DOI: 10.1088/0256-307X/34/5/050601
