With 87-Sr atoms confined in a one dimensional optical lattice, the frequency of the optical clock transition 5s^2 ^1S_0 - 5s5p ^3P_0 has been determined to be 429 228 004 229 872.9(5) Hz. The transition frequency was measured with the help of a fs-frequency comb against one of PTB's H-masers whose frequency was measured simultaneously by the PTB Cs fountain clock CSF1. The Sr optical frequency standard contributes with a fractional uncertainty of 1.5 10^-16 to the total uncertainty. The agreement of the measured transition frequency with previous measurements at other institutes supports the status of this transition as secondary representation of the second with the currently smallest uncertainty.
An Al$^+$ clock with $1.6\times10^{-18}$ systematic uncertainty and its frequency ratios
Physikalisch-Technische Bundesanstalt（德国联邦物理技术研究院）；Institut für Quantenoptik, Leibniz Universität Hannover（汉诺威莱布尼茨大学量子光学研究所）；Laboratoire Kastler Brossel, Sorbonne Université, CNRS, ENS-PSL Research University, Collège de France（索邦大学、法国国家科学研究中心、巴黎文理研究大学、法兰西公学院卡斯特尔-布罗塞尔实验室）
A strontium lattice clock with $3 \times 10^{-17}$ inaccuracy and its frequency
我们在PTB用两个铯原子喷泉钟测量了基于$^{87}$ Sr的光晶格钟的绝对频率，其不确定度为$3.9\times 10^{-16}$。这接近于当今SI秒的最佳实现的精度。$^{87}$ Sr中5s $^2$ $^1$ S $_0$-5s 5 p $^3$ P $_0$跃迁的绝对频率为429，228，004，229，873.13（17）Hz。我们的结果与最近在世界各地不同实验室进行的测量结果非常一致。我们将Sr频标的总系统不确定度提高了5倍，达到了$3\times 10^{-17}$，为基础研究、大地测量或光学钟评估的光学钟之间的频率比测量开辟了新的前景。
Absolute frequency measurement of the $^{40}$Ca$^{+}$ clock transition using a GNSS link to the SI second
Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften（奥地利科学院量子光学与量子信息研究所）；Universität Innsbruck, Institut für Experimentalphysik（因斯布鲁克大学实验物理研究所）；Alpine Quantum Technologies GmbH（阿尔卑斯量子技术有限公司）；Singapore University of Technology and Design（新加坡科技设计大学）；Qatar Center for Quantum Computing, College of Science and Engineering, Hamad Bin Khalifa University（哈马德·本·哈利法大学科学与工程学院卡塔尔量子计算中心）
International Optical Clock Comparison Using the European Optical Fiber Network
Istituto Nazionale di Ricerca Metrologica (INRIM)（意大利国家计量研究所）；Laboratoire Temps Espace (LNE-OP), Observatoire de Paris, Université PSL, Sorbonne Université, Université de Lille, LNE, CNRS（巴黎天文台时间空间实验室（LNE-OP））；Laboratoire de Physique des Lasers (LPL), Université Sorbonne Paris Nord, CNRS（索邦巴黎北大学激光物理实验室（LPL））；Physikalisch-Technische Bundesanstalt (PTB)（德国联邦物理技术研究院）
Comment on "Prospect of optical frequency standard based on a 43Ca+ ion"
最近对基于单个捕获的$^{43}$ Ca $^+$离子的光频率标准预期的频率不确定度的评估发表在Phys. Rev. A { \bf 72}（2005）043404中。该论文包含了一些有趣的信息，如系统频率偏移，但未能描述其不确定性，导致混淆准确性和精度。关于对频移的主要贡献的结论与所提出的计算不一致，并且省略了与先前公布的数据的比较。
We report on the first frequency ratio measurement of an $^{115}$In+ single ion clock and a $^{87}$Sr optical lattice clock. A hydrogen maser serves as a reference oscillator to measure the ratio by independent optical combs. Over more than 90 000 seconds of measurement time, the frequency ratio $f_{\rm{In^+}}/f_{\rm{Sr}}$ is determined to be 2.952 748 749 874 863 4(21) with relative uncertainty of $7.0 \times 10^{-16}$. The measurement creates a new connection in the network of frequency ratios of optical clocks.
Space-borne optical frequency references based on spectroscopy of atomic vapors may serve as an integral part of compact optical atomic clocks, which can advance global navigation systems, or can be utilized for earth observation missions as part of laser systems for cold atom gradiometers. Nanosatellites offer low launch-costs, multiple deployment opportunities and short payload development cycles, enabling rapid maturation of optical frequency references and underlying key technologies in space. Towards an in-orbit demonstration on such a platform, we have developed a CubeSat-compatible prot…
Compactness, robustness and autonomy of optical frequency references are prerequisites for reliable operation in mobile systems, on ground as well as in space. We present a standalone plug and play optical frequency reference device based on frequency modulation spectroscopy of the D2-transition in rubidium at 780 nm. After a single button press the hand-sized laser module, based on the micro-integrated laser-optical bench described in [J. Opt. Soc. Am. B 38, 1885-1891 (2021)], works fully autonomous and generates 6 mW of frequency stabilized light with a relative frequency instability of 1.4e…
An experimental method is developed for the robust frequency stabilization using a high-finesse cavity when the laser exhibits large intermittent frequency jumps. This is accomplished by applying an additional slow feedback signal from Doppler-free fluorescence spectroscopy in an atomic beam with increased frequency locking range. As a result, a stable and narrow-linewidth 556 nm laser maintains the frequency lock status for more than a week, and contributes to more accurate evaluation of the Yb optical lattice clock. In addition, the reference optical cavity is supported at vibration-insensit…
Optical fibers with interferometric path length stability by controlled heating for transmission of optical signals and as components in frequency standards
We report the absolute frequency measurement of the 5s2 1S0-5s5p 3P0 transition in 87Sr optical lattice clock (Sr1) at National Time Service Center (NTSC). Its systematic frequency shifts are evaluated carefully with a total relative uncertainty of 5.1E10-17. The measured absolute frequency is 429 228 004 229 872.91(18) Hz with a relative uncertainty of 4.13E10-16, with reference to the ensemble of primary and secondary frequency standards published in the Circular T bulletin by BIPM through a global navigation satellite system (GNSS) link.
With the uncertainty of the optical clocks improving to the order of 10-18, the probe light used to detect the clock transition has demonstrated nonnegligible Stark shift, provoking to precisely evaluate this shift. Here, we demonstrate a frequency modulation technique to realize a large measurement lever arm of the probe Stark shift with no cost of the measurement accuracy of the interleaved stabilization method. This frequency-modulated spectrum is theoretical described and experimental verified. The probe Stark shift coefficient of the 87Sr optical lattice clock is experimentally determined…
