液氮低温钙离子光钟的宏运动与附加微运动研究  

Characteristics of secular-and excess micro-motion of a liquid nitrogen-cooled Ca+ion optical clock

作　　者：马子晓 张宝林 黄垚 高克林 管桦 MA Zixiao;ZHANG Baolin;HUANG Yao;GAO Kelin;GUAN Hua(Innovation Academy of Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430071,China;University of Chinese Academy of Sciences,Beijing 100049,China;Wuhan Institute of Quantum Technology,Wuhan 430206,China;Hefei National Laboratory,Hefei 230088,China)

机构地区：[1]中国科学院精密测量科学与技术创新研究院,武汉430071 [2]中国科学院大学,北京100049 [3]武汉量子技术研究院,武汉430206 [4]合肥国家实验室,合肥230088

出　　处：《物理学报》2025年第9期168-176,共9页Acta Physica Sinica

基　　金：国家重点研发计划(批准号:2022YFB3904001,2022YFB3904004);科技创新2030-“量子通信与量子计算机”重大项目(批准号:2021ZD0300901);国家自然科学基金(批准号:12204494,12121004,12320101003,11934014);湖北省科学基金(批准号:2023EHA006,2022CFA013)资助的课题.

摘　　要：在离子光钟实验系统中,离子的运动效应是衡量一套光钟性能的主要指标之一,是目前限制各类不同离子光钟具有更低不确定度的关键影响因素.在第一套液氮低温钙离子光钟的基础上(2022 Phys.Rev.Appl.17034041),我们研制了新一套液氮钙离子光钟的物理系统,并对其离子囚禁装置进行了较大改进,主要包括以下两方面:通过引入射频电压的主动稳定装置,将液氮低温钙离子光钟的径向宏运动频率的长期漂移抑制到了小于1kHz水平;通过改进离子阱鞍点位置剩余电压的补偿方案,进一步将液氮低温钙离子光钟中附加微运动造成的频移抑制至小于1.0×10^(-19).这些改进有助于提升离子的冷却效率与提高离子温度的评估精度.通过对宏运动红蓝边带的测量,精确评估了Doppler冷却后离子的振动平均声子数,对应的离子温度为0.78 mK,接近Doppler冷却极限.此外,稳定的宏运动频率为下一步在液氮低温钙离子光钟上实施三维边带冷却创造了良好条件,也为推动液氮低温钙离子光钟的系统不确定度进一步降低至10^(-19)量级打下了基础.In ion optical clock systems,the motional effect of trapped ions is a key factor determining clock performance and currently representing a key limitation in achieving lower uncertainty between different ion-based optical clocks.According to the first liquid nitrogen-cooled Ca+ion optical clock(2022 Phys.Rev.Appl.17034041),we develop a new physical system for a second Ca+ion optical clock and make significant improvements to its ion trapping apparatus.These improvements primarily focus on two aspects.The first aspect is that we design and implement an active stabilization system for the RF voltage,which stabilizes the induced radio-frequency(RF)signal on the compensation electrodes by adjusting the amplitude of the RF source in real time.This method effectively suppresses long-term drifts in the radial secular motion frequencies to less than 1 kHz,achieving stabilized values of w_(x)=2π×3.522(2)MHz and w_(y)=2π×3.386(2)MHz.The induced RF signal is stabilized at 59121.43(12)μV,demonstrating the high precision of the stabilization system.The second aspect is that we optimize the application of compensation voltages by directly integrating the vertical compensation electrodes into an ion trap structure.This refinement can suppress excess micromotion in all three mutually orthogonal directions to an even lower level.Tuning the RF trapping frequency close to the magic trapping condition of the clock transition,we further evaluate the excess micromotion-induced frequency shift in the optical clock to be 2(1)×10^(-19).To quantitatively assess the secular-motion of the trapped ion,we measure the sideband spectra on the radial and axial motion modes,both red and blue sideband spectra.From these measurements,we accurately determine the mean phonon number in the three motional modes after Doppler cooling,corresponding to an average ion temperature of 0.78(39)mK,which is close to the Doppler cooling limit.The corresponding second-order Doppler shift is evaluated to be-(2.71±1.36)×10^(-18).The longterm stability of th

关 键 词：钙离子光钟 低温 宏运动 附加微运动 

分 类 号：O562[理学—原子与分子物理]