Absolute frequency measurement of the 40Ca+ S1/2 - D5/2 clock transition

TL;DR

This paper reports the first absolute frequency measurement of the 40Ca+ ion's clock transition with high precision, referencing a frequency comb to a Cs fountain clock, achieving near state-of-the-art accuracy and determining the g-factor of the D5/2 level.

Contribution

It presents the first absolute measurement of the 40Ca+ S1/2 - D5/2 transition frequency with 10^{-15} level accuracy using a frequency comb linked to a Cs fountain clock.

Findings

Measured the transition frequency as 411 042 129 776 393.2(1.0) Hz.

Determined the g-factor of the D5/2 level as 1.2003340(3).

Achieved fractional uncertainty within a factor of three of the Cs standard.

Abstract

We report on the first absolute transition frequency measurement at the 10^{-15} level with a single, laser-cooled 40Ca+ ion in a linear Paul trap. For this measurement, a frequency comb is referenced to the transportable Cs atomic fountain clock of LNE-SYRTE and is used to measure the S1/2-D5/2 electric-quadrupole transition frequency. After the correction of systematic shifts, the clock transition frequency f_Ca+ = 411 042 129 776 393.2 (1.0) Hz is obtained, which corresponds to a fractional uncertainty within a factor of three of the Cs standard. Future improvements are expected to lead to an uncertainty surpassing the best Cs fountain clocks. In addition, we determine the Lande g-factor of the D5/2 level to be gD5/2=1.2003340(3).