Improved Frequency Measurement of a One-Dimensional Optical Lattice Clock with a Spin-Polarized Fermionic⁸⁷Sr Isotope

Abstract

We demonstrate a one-dimensional optical lattice clock with a spin-polarized fermionic isotope designed to realize a collision-shift-free atomic clock with neutral atom ensembles.To reduce systematic uncertainties, we developed both Zeeman shift and vector light-shift cancellation techniques. By introducing both an H-maser and a Global Positioning System (GPS) carrier phase link, the absolute frequency of the 1 S 0 (F = 9/2) − 3 P 0 (F = 9/2) clock transition of the 87 Sr optical lattice clock is determined as 429,228,004,229,875(4) Hz, where the uncertainty is mainly limited by that of the frequency link. The result indicates that the Sr lattice clock will play an important role in the scope of the redefinition of the "second"by optical frequency standards.

An optical lattice clock with spin-polarized 87Sr atoms

“…The result is in excellent agreement with the values reported by the JILA group with a similar uncertainty [1] and by the Tokyo group with a 4 Hz error bar [9]. Obtained in independent experiments with significant differences in their implementation, this multiple redundancy strengthens the obtained results and further confirms the possibility to build high accuracy clocks with cold atoms confined in an optical lattice.…”

“…Altogether, the accuracy of the frequency measurement of the 1 S 0 − 3 P 0 clock transition of Sr has steadily improved by four orders of magnitude since its first direct measurement in 2003 [8]. Three independent measurements performed in Tokyo university [9], JILA [4] and SYRTE [10] were reported with a fractional uncertainty of 10 −14 giving excellent agreement. Recently, the JILA group improved their uncertainty down to 2.5 × 10 −15 [1], a value that is comparable to the frequency difference between the various primary standards throughout the world [11].…”

“…The major modification as compared to our previous evaluation is an improved control of the Zeeman effect. By applying a bias field of typically 0.1 mT and pumping atoms into extreme Zeeman states (we alternate measurements with m F = +9/2 and m F = −9/2) we cancel the first order Zeeman effect while getting a real time measurement of the actual magnetic field seen by the atoms [9]. The measured frequency of the 1 S 0 → 3 P 0 clock transition of 87 Sr is 429 228 004 229 873.6 (1.1) Hz.…”

Absolute frequency measurement of the magnesium intercombination transitionS01→P13

“…Systems using strontium and calcium [2,3,4,5,6,7] have recently been shown to outperform state-ofthe-art Cs clocks in terms of stability and the accuracy of some optical ion frequency standards is already limited by the accuracy of the best Cs clocks [8,9].…”

Feasibility of an optical fiber clock

“…The vector light-shifts of the components m F = ± 9 2 have the opposite signs. Zeeman shift and vector-light shift cancellation techniques have been developed in [60] based on the averaging of frequency measurements for two transitions ( 1 S 0 , F = 9 2 , m F = ± 9 2 ) − ( 3 P 0 , F = 9 2 , m F = ± 9 2 ). For the same parameters ∆n, L, U , and (e k · e B ) = 0, (e · e B ) = 1, δν t 9 2 = 41.5 mHz.…”