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