标题： 一小时内具有$6\times 10^{-19}$精度的光钟比对 显示英文标题

标题： Optical clock intercomparison with $6\times 10^{-19}$ precision in one hour

摘要： 在原子-光相干性方面的改进是量子信息科学、量子光学和精密计量学进步的基础。 光学原子钟需要具有卓越光学相干性的本地振荡器，因为对其超窄线宽钟跃迁进行光谱分析存在挑战。 激光稳定性的进展因此使得钟的精度迅速提高。 一种基于低温硅参考腔的新一类超稳定激光器最近展示了迄今为止最长的光学相干时间。 在本工作中，我们利用这种本地振荡器，并结合最先进的频率梳进行相干传递，与两个锶光学晶格钟一起实现了前所未有的钟稳定性。 通过反同步比较，两台钟的分数不稳定性被评估为$4.8\times 10^{-17}/\sqrt{\tau}$，平均时间为$\tau$秒。 同步探测揭示了由量子投影噪声主导的不稳定性为$3.5(2)\times10^{-17}/\sqrt{\tau}$，经过一小时的平均后精度达到$5.8(3)\times 10^{-19}$。 在如此短的时间尺度上测量亚$10^{-18}$级别的频率偏移将影响钟在量子传感和基础物理中的广泛应用。 例如，这种精度使得仅需20分钟就能分辨出1厘米高度变化引起的引力红移。 显示英文摘要

摘要： Improvements in atom-light coherence are foundational to progress in quantum information science, quantum optics, and precision metrology. Optical atomic clocks require local oscillators with exceptional optical coherence due to the challenge of performing spectroscopy on their ultra-narrow linewidth clock transitions. Advances in laser stabilization have thus enabled rapid progress in clock precision. A new class of ultrastable lasers based on cryogenic silicon reference cavities has recently demonstrated the longest optical coherence times to date. In this work we utilize such a local oscillator, along with a state-of-the-art frequency comb for coherence transfer, with two Sr optical lattice clocks to achieve an unprecedented level of clock stability. Through an anti-synchronous comparison, the fractional instability of both clocks is assessed to be $4.8\times 10^{-17}/\sqrt{\tau}$ for an averaging time $\tau$ in seconds. Synchronous interrogation reveals a quantum projection noise dominated instability of $3.5(2)\times10^{-17}/\sqrt{\tau}$, resulting in a precision of $5.8(3)\times 10^{-19}$ after a single hour of averaging. The ability to measure sub-$10^{-18}$ level frequency shifts in such short timescales will impact a wide range of applications for clocks in quantum sensing and fundamental physics. For example, this precision allows one to resolve the gravitational red shift from a 1 cm elevation change in only 20 minutes.