Takamoto Masao, Hong Feng-Lei, Higashi Ryoichi, Katori Hidetoshi
Engineering Research Institute, The University of Tokyo, Japan.
Nature. 2005 May 19;435(7040):321-4. doi: 10.1038/nature03541.
The precision measurement of time and frequency is a prerequisite not only for fundamental science but also for technologies that support broadband communication networks and navigation with global positioning systems (GPS). The SI second is currently realized by the microwave transition of Cs atoms with a fractional uncertainty of 10(-15) (ref. 1). Thanks to the optical frequency comb technique, which established a coherent link between optical and radio frequencies, optical clocks have attracted increasing interest as regards future atomic clocks with superior precision. To date, single trapped ions and ultracold neutral atoms in free fall have shown record high performance that is approaching that of the best Cs fountain clocks. Here we report a different approach, in which atoms trapped in an optical lattice serve as quantum references. The 'optical lattice clock' demonstrates a linewidth one order of magnitude narrower than that observed for neutral-atom optical clocks, and its stability is better than that of single-ion clocks. The transition frequency for the Sr lattice clock is 429,228,004,229,952(15) Hz, as determined by an optical frequency comb referenced to the SI second.
时间和频率的精确测量不仅是基础科学的前提条件，也是支持宽带通信网络以及全球定位系统（GPS）导航等技术的前提条件。国际单位制（SI）秒目前是通过铯原子的微波跃迁来实现的，其分数不确定度为10^(-15)（参考文献1）。由于光频梳技术在光频和射频之间建立了相干联系，作为具有卓越精度的未来原子钟，光钟已引起越来越多的关注。迄今为止，单囚禁离子和自由下落的超冷中性原子已展现出创纪录的高性能，接近最佳铯喷泉钟的性能。在此，我们报告一种不同的方法，其中囚禁在光晶格中的原子用作量子参考。“光晶格钟”展示出的线宽比中性原子光钟所观测到的窄一个数量级，并且其稳定性优于单离子钟。通过参考SI秒的光频梳确定，锶晶格钟的跃迁频率为429,228,004,229,952(15)赫兹。
