Strontium optical lattice clock at the National Time Service Center

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The Zeeman shift plays an important role in the evaluation of optical lattice clocks since a strong bias magnetic field is applied for departing Zeeman sublevels and defining a quantization axis. We demonstrated the frequency correction and uncertainty evaluation due to Zeeman shift in the 87Sr optical lattice clock at the National Time Service Center. The first-order Zeeman shift was almost completely removed by stabilizing the clock laser to the average frequency of the two Zeeman components of mF = ±9/2. The residual first-order Zeeman shift arose from the magnetic field drift between measurements of the two stretched-state center frequencies; the upper bound was inferred as 4(5) × 10−18. The quadratic Zeeman shift coefficient was experimentally determined as –23.0(4) MHz/T2 and the final Zeeman shift was evaluated as 9.20(7) × 10−17. The evaluation of the Zeeman shift is a foundation for overall evaluation of the uncertainty of an optical lattice clock. This measurement can provide more references for the determination of the quadratic coefficient of 87Sr.

Section: Methodsmentioning

confidence: 99%

An Evaluation of the Zeeman Shift of the 87Sr Optical Lattice Clock at the National Time Service Center

Yin

et al. 2020

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“…The error signal is calculated digitally from four clock cycle. After filtering using a PID (proportional, integral, derivative) controller, feedback is provided by a frequency correction signal to modulate the AOM2 [25]. The error signal was obtained after the clock laser had been locked to the atomic transition ( Figure 7a) along with the in-loop error signal stability of the 87 Sr optical lattice clock (Figure 7b).…”

Section: Closed-loop Operation Of 87 Sr Optical Lattice Clockmentioning

confidence: 99%

Recent Advances Concerning the 87Sr Optical Lattice Clock at the National Time Service Center

Wang

et al. 2018

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We review recent experimental progress concerning the 87Sr optical lattice clock at the National Time Service Center in China. Hertz-level spectroscopy of the 87Sr clock transition for the optical lattice clock was performed, and closed-loop operation of the optical lattice clock was realized. A fractional frequency instability of 2.8 × 10−17 was attained for an averaging time of 2000 s. The Allan deviation is found to be 1.6 × 10−15/τ1/2 and is limited mainly by white-frequency-noise. The Landé g-factors of the (5s2)1S0 and (5s5p)3P0 states in 87Sr were measured experimentally; they are important for evaluating the clock’s Zeeman shifts. We also present recent work on the miniaturization of the strontium optical lattice clock for space applications.

“…Currently, all the demonstrated space-borne cold atom clocks and BEC are based on alkali atoms [1,7,12]. However, neutral atom optical clocks are based on alkaline earth(-like) atoms, such as Mg [16], Ca [17], Sr [18,19], Yb [20], and Hg [21], some of which are also interested in BEC [22][23][24]. A distinctive advantage of these alkaline earth(-like) atoms over alkali atoms is the existence of spin-forbidden transition of 1 S 0 − 3 P 1 by which one can perform a narrow-line laser cooling [25,26].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Narrow-Line Laser Cooling and Trapping of Sr Atoms in Microgravity Environments

Ren

Liu

et al. 2020

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Obtaining ultracold alkaline earth(-like) atoms in space encounters the problem of performing narrow-line laser cooling in microgravity environments ( μ -gEs). This paper reports an analysis of the magneto-optical trap (MOT) based on the narrow-line transition in 88 Sr, while paying special attention to the role of the gravity. This analysis suggests the MOTs based on narrow-line transitions cannot be cold and dense enough in a μ -gE. We thus propose a strategy: that one can use a dual-frequency MOT to realize a low-temperature, high density, and high transfer efficiency, narrow-line red MOT in μ -gEs.