中国物理B ›› 2021, Vol. 30 ›› Issue (7): 73702-073702.doi: 10.1088/1674-1056/abfc3e

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Numerical analysis of motional mode coupling of sympathetically cooled two-ion crystals

Li-Jun Du(杜丽军)1,2, Yan-Song Meng(蒙艳松)1,2,†, Yu-Ling He(贺玉玲)1,2, and Jun Xie(谢军)2,3   

  1. 1 China Academy of Space Technology(Xi'an), Xi'an 710100, China;
    2 National Key Laboratory of Science and Technology on Space Microwave, China Academy of Space Technology(Xi'an), Xi'an 710100, China;
    3 China Academy of Space Technology, Beijing 100094, China
  • 收稿日期:2021-01-03 修回日期:2021-03-21 接受日期:2021-04-28 出版日期:2021-06-22 发布日期:2021-07-09
  • 通讯作者: Yan-Song Meng E-mail:yansmeng@163.com
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 11803023), the Equipment Pre-research Foundation (Grant No. 6142411196406), and Key Research and Development Program of Shaanxi Province, China (Grant No. 2017ZDXM-GY-113).

Numerical analysis of motional mode coupling of sympathetically cooled two-ion crystals

Li-Jun Du(杜丽军)1,2, Yan-Song Meng(蒙艳松)1,2,†, Yu-Ling He(贺玉玲)1,2, and Jun Xie(谢军)2,3   

  1. 1 China Academy of Space Technology(Xi'an), Xi'an 710100, China;
    2 National Key Laboratory of Science and Technology on Space Microwave, China Academy of Space Technology(Xi'an), Xi'an 710100, China;
    3 China Academy of Space Technology, Beijing 100094, China
  • Received:2021-01-03 Revised:2021-03-21 Accepted:2021-04-28 Online:2021-06-22 Published:2021-07-09
  • Contact: Yan-Song Meng E-mail:yansmeng@163.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 11803023), the Equipment Pre-research Foundation (Grant No. 6142411196406), and Key Research and Development Program of Shaanxi Province, China (Grant No. 2017ZDXM-GY-113).

摘要: A two-ion pair in a linear Paul trap is extensively used in the research of the simplest quantum-logic system; however, there are few quantitative and comprehensive studies on the motional mode coupling of two-ion systems yet. This study proposes a method to investigate the motional mode coupling of sympathetically cooled two-ion crystals by quantifying three-dimensional (3D) secular spectra of trapped ions using molecular dynamics simulations. The 3D resonance peaks of the 40Ca+-27Al+ pair obtained by using this method were in good agreement with the 3D in- and out-of-phase modes predicted by the mode coupling theory for two ions in equilibrium and the frequency matching errors were lower than 2%. The obtained and predicted amplitudes of these modes were also qualitatively similar. It was observed that the strength of the sympathetic interaction of the 40Ca+-27Al+ pair was primarily determined by its axial in-phase coupling. In addition, the frequencies and amplitudes of the ion pair's resonance modes (in all dimensions) were sensitive to the relative masses of the ion pair, and a decrease in the mass mismatch enhanced the sympathetic cooling rates. The sympathetic interactions of the 40Ca+-27Al+ pair were slightly weaker than those of the 24Mg+-27Al+ pair, but significantly stronger than those of 9Be+-27Al+. However, the Doppler cooling limit temperature of 40Ca+ is comparable to that of 9Be+ but lower than approximately half of that of 24Mg+. Furthermore, laser cooling systems for 40Ca+ are more reliable than those for 24Mg+ and 9Be+. Therefore, 40Ca+ is probably the best laser-cooled ion for sympathetic cooling and quantum-logic operations of 27Al+ and has particularly more notable comprehensive advantages in the development of high reliability, compact, and transportable 27Al+ optical clocks. This methodology may be extended to multi-ion systems, and it will greatly aid efforts to control the dynamic behaviors of sympathetic cooling as well as the development of low-heating-rate quantum logic clocks.

关键词: sympathetic cooling, coupled oscillations, secular motion, radio-frequency ion traps

Abstract: A two-ion pair in a linear Paul trap is extensively used in the research of the simplest quantum-logic system; however, there are few quantitative and comprehensive studies on the motional mode coupling of two-ion systems yet. This study proposes a method to investigate the motional mode coupling of sympathetically cooled two-ion crystals by quantifying three-dimensional (3D) secular spectra of trapped ions using molecular dynamics simulations. The 3D resonance peaks of the 40Ca+-27Al+ pair obtained by using this method were in good agreement with the 3D in- and out-of-phase modes predicted by the mode coupling theory for two ions in equilibrium and the frequency matching errors were lower than 2%. The obtained and predicted amplitudes of these modes were also qualitatively similar. It was observed that the strength of the sympathetic interaction of the 40Ca+-27Al+ pair was primarily determined by its axial in-phase coupling. In addition, the frequencies and amplitudes of the ion pair's resonance modes (in all dimensions) were sensitive to the relative masses of the ion pair, and a decrease in the mass mismatch enhanced the sympathetic cooling rates. The sympathetic interactions of the 40Ca+-27Al+ pair were slightly weaker than those of the 24Mg+-27Al+ pair, but significantly stronger than those of 9Be+-27Al+. However, the Doppler cooling limit temperature of 40Ca+ is comparable to that of 9Be+ but lower than approximately half of that of 24Mg+. Furthermore, laser cooling systems for 40Ca+ are more reliable than those for 24Mg+ and 9Be+. Therefore, 40Ca+ is probably the best laser-cooled ion for sympathetic cooling and quantum-logic operations of 27Al+ and has particularly more notable comprehensive advantages in the development of high reliability, compact, and transportable 27Al+ optical clocks. This methodology may be extended to multi-ion systems, and it will greatly aid efforts to control the dynamic behaviors of sympathetic cooling as well as the development of low-heating-rate quantum logic clocks.

Key words: sympathetic cooling, coupled oscillations, secular motion, radio-frequency ion traps

中图分类号:  (Ion trapping)

  • 37.10.Ty
37.10.Rs (Ion cooling) 37.90.+j (Other topics in mechanical control of atoms, molecules, and ions) 31.15.xv (Molecular dynamics and other numerical methods)