Characterization of rf field-induced a.c. Zeeman shift in multi-level highly charged ions

TL;DR

This paper experimentally characterizes the rf-induced a.c. Zeeman shift in highly charged ions, crucial for optical clock accuracy, using quantum logic spectroscopy and measuring magnetic field components.

Contribution

It demonstrates a method to measure the a.c. Zeeman shift in highly charged ions and confirms its small influence, with techniques applicable to other multi-level atomic systems.

Findings

Measured transverse a.c. magnetic field via Autler-Townes splitting.

Probed the hyperfine transition in Be+ to assess shift influence.

Confirmed minimal impact of a.c. Zeeman shift in highly charged ions.

Abstract

Characterization of the trap rf induced a.c. Zeeman shift is essential for achieving high accuracy in optical ion clocks. In this work, we demonstrate the experimental characterization of this shift using highly charged $\mathrm{Ca}^{14+}$. The transverse component of the a.c. magnetic field is measured using the Autler-Townes splitting of the equally-spaced Zeeman components of the $^{3}\mathrm{P}_1$ when the Zeeman splitting is close to resonance with the trap rf drive frequency. We observe the resulting modulation by performing quantum logic spectroscopy using the co-trapped $\mathrm{Be}^{+}$. The longitudinal component is measured from probing the $\mathrm{Be}^{+}$ magnetic field-insensitive hyperfine transition $|F=2,m_F=0 \rangle \rightarrow | F=1,m_F=0 \rangle$. We confirm the small influence of the a.c. Zeeman shift in highly charged ions. The employed techniques can easily be transferred to other multi-level atomic systems.