Evaluation of the systematic shifts of a ${}^{40}\textrm{Ca}^+-{}^{27}\textrm{Al}^+$ optical clock

Abstract

We report the evaluation of the systematic shifts and the total uncertainty of an 27 Al + optical clock sympathetically cooled by a 40 Ca + ion. Due to its relatively low Doppler cooling limit and the suitability of its mass ratio to the 27 Al + ion, the time dilation shift of the secular motion of our 40 Ca + − 27 Al + clock is smaller than the shift of a 25 Mg + − 27 Al + clock. The total systematic uncertainty of our 40 Ca + − 27 Al + quantum logic clock has been estimated to be 7.6 × 10 −18 , which was mainly limited by the uncertainty of the quadratic Zeeman shift.

Scalable quantum logic spectroscopy

“…The internal state of the spectroscopy ion (SI) is transferred via a shared mode of motion to the LI where it can be detected via photon scattering. The first demonstration of QLS was with 27 Al + [7,8], which now serves as a frequency reference in atomic clocks [9][10][11][12]. Variations on the QLS technique have been developed with several aims: to demonstrate Hz-level precision spectroscopy for atomic clocks [9][10][11][12], to perform correlation spectroscopy [13], to work far offresonance from an optical transition [2,14], or to operate in thermal motion [15,16].…”

“…The first demonstration of QLS was with 27 Al + [7,8], which now serves as a frequency reference in atomic clocks [9][10][11][12]. Variations on the QLS technique have been developed with several aims: to demonstrate Hz-level precision spectroscopy for atomic clocks [9][10][11][12], to perform correlation spectroscopy [13], to work far offresonance from an optical transition [2,14], or to operate in thermal motion [15,16]. So far QLS has only been performed on up to two SIs [13] and the issue of scaling QLS techniques to larger ion numbers [17] is an open experimental question.…”