# Frequency measurement of the $^{1}\mathrm{S}_{0}, F=5/2\leftrightarrow\,^{3}\mathrm{P}_{1}, F=7/2$ transition of $^{27}$Al$^{+}$ via quantum logic spectroscopy with $^{40}$Ca$^{+}$

## TL;DR

This paper uses quantum logic spectroscopy with a mixed ion crystal to precisely measure the frequency of a specific transition in $^{27}$Al$^{+}$, achieving high accuracy by referencing a $^{40}$Ca$^{+}$ clock transition.

## Contribution

The study demonstrates a novel measurement of the $^{27}$Al$^{+}$ intercombination transition frequency using quantum logic spectroscopy with interleaved Ramsey measurements.

## Key findings

- Transition frequency measured as 1122 842 857 334 736(93) Hz.
- Landé g-factor of the excited state determined as 0.428132(2).
- High-precision frequency reference established for $^{27}$Al$^{+}$ transition.

## Abstract

We perform quantum logic spectroscopy with a $^{27}$Al$^{+}$/$^{40}$Ca$^{+}$ mixed ion crystal in a linear Paul trap for a measurement of the $(3s^{2})\,^{1}\mathrm{S}_{0} \leftrightarrow \, (3s3p)\,^{3}\mathrm{P}_{1}, F=7/2$ intercombination transition in $^{27}$Al$^{+}$. Towards this end, Ramsey spectroscopy is used for probing the transition in $^{27}$Al$^{+}$ and the $(4s^{2})\,\mathrm{S}_{1/2} \leftrightarrow \, (4s3d)\,\mathrm{D}_{5/2}$ clock transition in $^{40}$Ca$^{+}$ in interleaved measurements. By using the precisely measured frequency of the clock transition in $^{40}$Ca$^{+}$ as a frequency reference, we determine the frequency of the intercombination line to be $\nu_{^{1}\mathrm{S}_{0} \leftrightarrow \,^{3}\mathrm{P}_{1},F=7/2}$=1122 842 857 334 736(93) Hz and the Land\'e g-factor of the excited state to be $g_{^{3}\mathrm{P}_{1}, F=7/2}$=0.428132(2).