线形Paul阱中镉113离子基态超精细结构的高精度测量

113Cd+ ions are found promising applications in the frequency metrology, quantum information processing and the fundamental physics, all of which relate to the ground-state hyperfine structure of cadmium ions. However, there are few of high-precision measurements of the ground-state hyperfine splitting of 113Cd+ in the past decades, and the precision of the existing results is far from the mentioned applications. Recently, we measured the ground-state hyperfine splitting of the laser-cooled cadmium ions in a linear quadrupole Paul trap with the techniques of laser cooling, laser pump and fluorescence detection. The obtained results of 113Cd+ consistents with the up-to-date measurement by other groups very well and the precision is slightly improved from 1.3E-11 to 7.9E-12. In this project, we are going to improve the measurement precision of the ground-state hyperfine structure of 113Cd+ to 5E-13 level based on our previous reseach. In order to achieve this object, we are going to study the second-order Zeeman shift and the second-order Doppler effect during the measurement more closely than before to improve the frequency shift corrections. By this project, the ground-state hyperfine structure constant of 113Cd+ ions is expected to measured at the 5E-13 level for the first time in the world, which could support the theoretical research of the atomic structure and open a new way for 113Cd+ ions in the applications of frequency standards and quantum information processing.

镉113离子在量子频标、量子信息和基础物理研究等领域具有重要应用前景，镉113离子基态超精细结构与这些应用息息相关，但目前对其高精度的实验测量很少，现有测量数据精度不能满足应用需求。在前期的研究中，我们采用激光冷却、激光光泵浦和光检测技术，对囚禁在线形四极Paul阱中的镉离子的基态超精细分裂跃迁频率进行了测量，其中镉113离子的测量结果与国际上最新报道的结果吻合，测量精度略有提高,由1.3E-11提高到7.9E-12。在本项目中，我们计划在前期工作基础上，把镉113离子基态超精细结构测量精度提高到5E-13水平。为了实现这个目的，我们要进一步研究测量过程中二阶Zeeman频移和二阶Doppler效应的影响，提高相应修正精度。本课题将首次给出精度达到5E-13水平的镉113离子基态超精细结构常数，该结果将促进原子结构等理论研究，并在频标和量子信息等领域得到应用。

镉113离子在量子频标、量子信息和基础物理研究等领域具有重要应用前景，镉113离子基态超精细结构与这些应用息息相关，但目前对其高精度的实验测量很少，现有测量数据精度不能满足应用需求。本项目的研究目标是实现对镉113离子基态超精细结构的高精度测量，测量精度达到5E-13水平。为了实现该目标，课题组对离子阱进行了优化设计，将微波天线集成于离子阱电极中；完善了离子阱物理系统的磁屏蔽罩，并利用磁通门对离子阱附近磁场实施主动稳定控制；优化了系统光路的设计，并对激光频率和功率进行了主动控制；利用FPGA技术自制了高精度的时序控制电路；实现了系统闭环锁定，并优化了系统各个主要运行参数；深入研究了镉离子在阱中的二阶Zeeman频移和二阶Doppler频移，提高相应修正精度；测量了系统海拔高度，计算了系统引力红移；将中国计量院的UTC-NIM信号传输到清华大学作为测量参考信号，保证了测量基准的精度。最终，镉113离子基态超精细结构实验测量不确定度达到6.6e-14，超出美国JPL测量精度约200倍，该结果显著优于本课题计划达到的测量精度。镉113离子基态超精细能级分裂频率值的高精度测量，完善了该元素原子结构数据的精度，为原子结构与原子物理相关基础研究提供了实验数据支撑。同时，镉113离子非常适合用于微波原子钟的研制，该课题的测量结果也将有力的推动镉113离子阱微波钟的发展。