20天内三种全光时间尺度的相位连续对比
Phase-continuous comparison of three all-optical time scales over 20 days
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中文总结 AI 辅助
该研究研发三种光飞轮振荡器，结合锶光频标准生成连续20天的全光时间尺度，其短期稳定性优于氢脉泽，数天平均后相对不稳定度<10^-16，有望成为未来计时技术。
中文摘要 AI 辅助
过去二十年，光频标准发展迅速，有望通过光频重新定义国际单位制（SI）秒。但时间尺度未显著提升，因其仍完全依赖射频飞轮振荡器（主要是氢脉泽），该振荡器受不完全采样噪声（即迪克效应）限制性能。为充分利用光频标准的卓越稳定性和准确度，时间尺度需采用比氢脉泽短期（<10^4秒）稳定性高几个数量级的光飞轮。本文介绍三种光飞轮振荡器：两个低温硅腔和一个碘光钟，其短期稳定性优于氢脉泽，长期稳定性与氢脉泽相当。用高可用率锶光频标准校准每个光飞轮，生成三个并行全光时间尺度，连续运行超20天。相互对比时，这些全光时间尺度经数天平均后，相对不稳定度<10^-16；在约6小时的典型校准间隙，累积时间差约20皮秒，整个测量周期总时间差<100皮秒。随着长距离光纤链路普及及光飞轮、光频标准商业化，预计全光时间尺度将成为计时的未来。
英文摘要
Optical frequency standards have progressed rapidly over the past two decades, leading to the anticipated redefinition of the SI second by an optical frequency. However, time scales have not yet significantly improved despite this development because they are still fully reliant on rf flywheel oscillators, mostly hydrogen masers, which impose a performance limit related to incompletely sampled noise known as the Dick effect. To best benefit from the exceptional stability and accuracy of optical frequency standards, time scales must employ optical flywheels with orders-of-magnitude better short-term (<$10^4$ s) stability than masers. Here, we introduce three optical flywheel oscillators (two cryogenic silicon cavities and one iodine optical clock) with superior short-term stability than hydrogen masers and long-term stability on par with masers. Steering each optical flywheel with a high-uptime Sr optical frequency standard generates three parallel all-optical time scales with continuous operation over >20 days. When compared with each other, these all-optical time scales achieve <$10^{-16}$ relative instability after just a few days of averaging. During typical steering gaps of ~6 hours, the accumulated time difference is ~20 ps, leading to the total time difference of <100 ps over the full measurement period. With the proliferation of long-distance optical fiber links and commercialization of optical flywheels and frequency standards, we anticipate all-optical time scales to be the future of timekeeping.
