Journal Article

Cryogenic optical lattice clocks

Ushijima, Ichiro, Takamoto, Masao, Das, Manoj, Ohkubo, Takuya, Katori, Hidetoshi

2015

Overview

A pair of 87 Sr optical lattice clocks with a statistical agreement of 2 × 10 −18 within 6,000 s has been developed. To this end, the behaviour of the blackbody radiation—a major perturbation for optical lattice clocks—was directly investigated. The accuracy of atomic clocks relies on the superb reproducibility of atomic spectroscopy, which is accomplished by careful control and the elimination of environmental perturbations on atoms. To date, individual atomic clocks have achieved a 10 −18 level of total uncertainties 1 , 2 , but a two-clock comparison at the 10 −18 level has yet to be demonstrated. Here, we demonstrate optical lattice clocks with 87 Sr atoms interrogated in a cryogenic environment to address the blackbody radiation-induced frequency shift 3 , which remains the primary source of systematic uncertainty 2 , 4 , 5 , 6 and has initiated vigorous theoretical 7 , 8 and experimental 9 , 10 investigations. The systematic uncertainty for the cryogenic clock is evaluated to be 7.2 × 10 −18 , which is expedited by operating two such cryo-clocks synchronously 11 , 12 . After 11 measurements performed over a month, statistical agreement between the two cryo-clocks reached 2.0 × 10 −18 . Such clocks' reproducibility is a major step towards developing accurate clocks at the low 10 −18 level, and is directly applicable as a means for relativistic geodesy 13 .

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 140/125 / 639/766/36 / Applied and Technical Physics / Atomic clocks / Blackbody / Clocks / Frequency shift / Geodesy / letter / Optical lattices / Physics / Quantum Physics / Reproducibility / Uncertainty