The isomeric transition of thorium-229(229Th),as the only known laser-accessible nuclear transition,offers the possibility for the development of a new generation of optical clocks.Solid-state nuclear optical clock...The isomeric transition of thorium-229(229Th),as the only known laser-accessible nuclear transition,offers the possibility for the development of a new generation of optical clocks.Solid-state nuclear optical clock based on229Th-doped crystals or thin films has attracted much attention due to its potential advantages in high stability,miniaturization,and robustness.This paper reviews the research progress of solid-state nuclear optical clock materials,analyzes the preparation,defects,and properties of the candidate solid material systems for229Th,explores the influence of the local crystal environment on the nuclear transition,focuses on introducing the latest research results of crystal materials such as Th-doped CaF2and LiSrAlF6,and looks forward to the future development direction of this field.It could provide a reference for the material selection and optimization of solid-state nuclear optical clocks.展开更多
Recent advances in atomic optical clocks based on electronic transitions have achieved frequency uncertainties at the10-19level,enabling wide applications in testing variations of physical constants,exploring dark ...Recent advances in atomic optical clocks based on electronic transitions have achieved frequency uncertainties at the10-19level,enabling wide applications in testing variations of physical constants,exploring dark matter signatures,and enhancing precision metrology for position,navigation,and timing systems.To pursue higher-precision optical clocks,the development of nuclear optical clocks has emerged,with the229Th system distinguished by its unique low-lying isomeric state at~8.4 eV and a natural linewidth of approximately 100μHz,promising uncertainties below 10-19.The intrinsic insensitivity of nuclear transitions to external perturbations and their subatomic-scale spatial confinement provide significant advantages over electronic transitions in mitigating environmental shifts.Recent experimental breakthroughs include the excitation of the nuclear clock transition in solid-state229Th-doped crystals with spectral resolution at the k Hz level.However,critical challenges persist,particularly in implementing effective laser excitation schemes(e.g.,via the electronic bridge mechanism)and closed-loop quantum control in trapped ion systems.Addressing these requires comprehensive understanding of complex many-body interactions in229Th,encompassing electronic structure,nuclear deformation,hyperfine and field shift,and solid-state environmental coupling.This review synthesizes recent advancements in(i)the characterization of nuclear and atomic structures of the229Th nuclear clock,and(ii)precise evaluation and mitigation of external perturbations affecting the clock transitions.The analysis provides a solid theoretical and experimental foundation for optimizing229Th-based nuclear clock performance.展开更多
针对相干布局囚禁(Coherent Population Trapping,CPT)原子钟的比例积分微分(Proportional-Integral-Differential,PID)参数优化问题,提出一种基于神经网络的全局寻优方法。首先通过数学建模模拟CPT原子钟的微波锁定过程,使用数字PID控...针对相干布局囚禁(Coherent Population Trapping,CPT)原子钟的比例积分微分(Proportional-Integral-Differential,PID)参数优化问题,提出一种基于神经网络的全局寻优方法。首先通过数学建模模拟CPT原子钟的微波锁定过程,使用数字PID控制算法实现频率稳定。采用蒙特卡洛方法生成10000组不同PID参数(Kp,Ki,Kd)的系统响应数据,构建包含输入层、两层隐藏层及输出层的全连接神经网络模型,以均方误差(Mean Squared Error,MSE)为性能指标,建立参数与性能的非线性映射关系。试验结果表明,优化后的PID参数(Kp=0.4960,Ki=0.0054,Kd=0.0016)使CPT原子钟的锁定时间从110 s缩短至30 s,提速73%;万秒Allan偏差(Allan Deviation,AD)提升1.5倍,验证了方法的有效性。与传统Ziegler-Nichols方法相比,神经网络通过全局映射避免了局部最优问题,且计算效率提升显著,为CPT原子钟的高性能控制提供了新途径。展开更多
主动型氢原子钟作为守时型原子钟,在国际时间尺度的产生与保持中发挥着重要作用。自2014年国际权度局(International Bureau of Weights and Measures,BIPM)修改权重计算方法后,氢原子钟的权重占比持续提升。随着国产主动型氢原子钟的...主动型氢原子钟作为守时型原子钟,在国际时间尺度的产生与保持中发挥着重要作用。自2014年国际权度局(International Bureau of Weights and Measures,BIPM)修改权重计算方法后,氢原子钟的权重占比持续提升。随着国产主动型氢原子钟的技术迭代进步,有必要开展国产主动型氢原子钟参与国际守时的性能评估,对提升国产原子钟在协调世界时产生与保持中的贡献度具有战略意义。首先介绍了主动型氢原子钟在国际标准时间产生中起到的主要作用,继而以频率稳定度和“可预测性”作为主要评估参数,对国产主动型氢原子钟参与国际守时的性能开展评估。评估结果显示,国产主动型氢原子钟的日频率稳定度优于1E-15,长期稳定度优于5E-16,与国际同类产品性能相当,而“可预测性”仍存在可提升空间,后续需进一步优化提升,进一步巩固并提升我国在国际标准时间体系中的影响力与话语权。展开更多
基金supported by Zhangjiang Laboratory(Grant No.ZJSP21A001D)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0920000)the National Natural Science Foundation of China(Grant Nos.12341402 and 12341403)。
摘要The isomeric transition of thorium-229(229Th),as the only known laser-accessible nuclear transition,offers the possibility for the development of a new generation of optical clocks.Solid-state nuclear optical clock based on229Th-doped crystals or thin films has attracted much attention due to its potential advantages in high stability,miniaturization,and robustness.This paper reviews the research progress of solid-state nuclear optical clock materials,analyzes the preparation,defects,and properties of the candidate solid material systems for229Th,explores the influence of the local crystal environment on the nuclear transition,focuses on introducing the latest research results of crystal materials such as Th-doped CaF2and LiSrAlF6,and looks forward to the future development direction of this field.It could provide a reference for the material selection and optimization of solid-state nuclear optical clocks.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB0920100 and XDB0920101)the National Natural Science Foundation of China(Grant Nos.12174402,12393821,12274417)the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-055)。
摘要Recent advances in atomic optical clocks based on electronic transitions have achieved frequency uncertainties at the10-19level,enabling wide applications in testing variations of physical constants,exploring dark matter signatures,and enhancing precision metrology for position,navigation,and timing systems.To pursue higher-precision optical clocks,the development of nuclear optical clocks has emerged,with the229Th system distinguished by its unique low-lying isomeric state at~8.4 eV and a natural linewidth of approximately 100μHz,promising uncertainties below 10-19.The intrinsic insensitivity of nuclear transitions to external perturbations and their subatomic-scale spatial confinement provide significant advantages over electronic transitions in mitigating environmental shifts.Recent experimental breakthroughs include the excitation of the nuclear clock transition in solid-state229Th-doped crystals with spectral resolution at the k Hz level.However,critical challenges persist,particularly in implementing effective laser excitation schemes(e.g.,via the electronic bridge mechanism)and closed-loop quantum control in trapped ion systems.Addressing these requires comprehensive understanding of complex many-body interactions in229Th,encompassing electronic structure,nuclear deformation,hyperfine and field shift,and solid-state environmental coupling.This review synthesizes recent advancements in(i)the characterization of nuclear and atomic structures of the229Th nuclear clock,and(ii)precise evaluation and mitigation of external perturbations affecting the clock transitions.The analysis provides a solid theoretical and experimental foundation for optimizing229Th-based nuclear clock performance.
摘要主动型氢原子钟作为守时型原子钟,在国际时间尺度的产生与保持中发挥着重要作用。自2014年国际权度局(International Bureau of Weights and Measures,BIPM)修改权重计算方法后,氢原子钟的权重占比持续提升。随着国产主动型氢原子钟的技术迭代进步,有必要开展国产主动型氢原子钟参与国际守时的性能评估,对提升国产原子钟在协调世界时产生与保持中的贡献度具有战略意义。首先介绍了主动型氢原子钟在国际标准时间产生中起到的主要作用,继而以频率稳定度和“可预测性”作为主要评估参数,对国产主动型氢原子钟参与国际守时的性能开展评估。评估结果显示,国产主动型氢原子钟的日频率稳定度优于1E-15,长期稳定度优于5E-16,与国际同类产品性能相当,而“可预测性”仍存在可提升空间,后续需进一步优化提升,进一步巩固并提升我国在国际标准时间体系中的影响力与话语权。