Coherent excitation of the highly forbidden electric octupole transition in ${}^{172}$Yb$^+$

TL;DR

This paper reports the first coherent excitation of a highly forbidden electric octupole transition in a single ${}^{172}$Yb$^+$ ion, achieving unprecedented measurement precision and enabling new physics searches.

Contribution

It demonstrates the first coherent excitation of the E3 transition in ${}^{172}$Yb$^+$ and provides highly precise frequency measurements, advancing atomic clock and fundamental physics research.

Findings

Transition frequency measured with 2.4 Hz uncertainty

Magnetic field environment mapped using E2 transition

Measurement accuracy improved by factors of 10^5 to 3×10^5

Abstract

We report on the first coherent excitation of the highly forbidden $^2S_{1/2}\rightarrow{}^2F_{7/2}$ electric octupole (E3) transition in a single trapped ${}^{172}$Yb$^+$ ion, an isotope without nuclear spin. Using the transition in ${}^{171}$Yb$^+$ as a reference, we determine the transition frequency to be $642\,116\,784\,950\,887.6(2.4)\,$Hz. We map out the magnetic field environment using the forbidden $^2S_{1/2} \rightarrow{}^2D_{5/2}$ electric quadrupole (E2) transition and determine its frequency to be $729\,476\,867\,027\,206.8(4.4)\,$Hz. Our results are a factor of $1\times10^5$ ($3\times10^{5}$) more accurate for the E2 (E3) transition compared to previous measurements. The results open up the way to search for new physics via precise isotope shift measurements and improved tests of local Lorentz invariance using the metastable $^2F_{7/2}$ state of Yb$^+$.