JILA, NIST and University of Colorado, 440 UCB, Boulder, Colorado 80309, USA.
Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
Phys Rev Lett. 2019 Oct 25;123(17):173201. doi: 10.1103/PhysRevLett.123.173201.
We report on the first timescale based entirely on optical technology. Existing timescales, including those incorporating optical frequency standards, rely exclusively on microwave local oscillators owing to the lack of an optical oscillator with the required frequency predictability and stability for reliable steering. We combine a cryogenic silicon cavity exhibiting improved long-term stability and an accurate ^{87}Sr lattice clock to form a timescale that outperforms them all. Our timescale accumulates an estimated time error of only 48±94 ps over 34 days of operation. Our analysis indicates that this timescale is capable of reaching a stability below 1×10^{-17} after a few months of averaging, making timekeeping at the 10^{-18} level a realistic prospect.
我们报告了第一个完全基于光学技术的时标。现有的时标，包括那些结合了光学频率标准的时标，由于缺乏具有所需频率可预测性和稳定性的光学振荡器，因此完全依赖于微波本振。我们结合了一个具有改进的长期稳定性的低温硅腔和一个精确的 ^{87}Sr 晶格钟，形成了一个在所有方面都表现出色的时标。我们的时标在 34 天的运行中累积的估计时间误差仅为 48±94 皮秒。我们的分析表明，这个时标在经过几个月的平均后，有能力达到低于 1×10^{-17}的稳定性，因此达到 10^{-18}水平的计时是一个现实的前景。
