# A precision measurement of the electron's electric dipole moment using trapped molecular ions

## TL;DR

This paper reports a highly sensitive measurement of the electron's electric dipole moment using trapped molecular ions, achieving a new upper bound and demonstrating the technique's potential for future improvements.

## Contribution

First precision measurement of the eEDM with trapped molecular ions using long spin interrogation times, enhancing sensitivity and systematic error rejection.

## Key findings

- Set an upper bound of |d_e| < 1.3 x 10^{-28} e·cm
- Confirmed previous upper bounds with an independent method
- Demonstrated long coherence times over 700 ms

## Abstract

We describe the first precision measurement of the electron's electric dipole moment (eEDM, $d_e$) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on $^{180}{\rm Hf}^{19}{\rm F}^{+}$ in its metastable $^{3}\Delta_{1}$ electronic state, we obtain $d_e = (0.9 \pm 7.7_{\rm stat} \pm 1.7_{\rm syst}) \times 10^{-29}\,e\,{\rm cm}$, resulting in an upper bound of $|d_e| < 1.3 \times 10^{-28}\,e\,{\rm cm}$ (90% confidence). Our result provides independent confirmation of the current upper bound of $|d_e| < 9.3 \times 10^{-29}\,e\,{\rm cm}$ [J. Baron $\textit{et al.}$, Science $\textbf{343}$, 269 (2014)], and offers the potential to improve on this limit in the near future.