Measurement of dipole matrix elements with a single trapped ion

TL;DR

This paper introduces a novel method using a single trapped ion to directly measure atomic dipole matrix elements, providing precise values and resolving previous discrepancies in atomic physics data.

Contribution

The authors develop a new technique based on quantum information methods to measure dipole matrix elements directly, applicable to various atomic species.

Findings

Measured the Ca II H line dipole matrix element as 2.8928(43) ea₀.

Deduced the P₁/₂ state lifetime as 6.904(26) ns, aligning with theoretical predictions.

Resolved a longstanding discrepancy between calculated and experimental atomic data.

Abstract

We demonstrate a new method for the direct measurement of atomic dipole transition matrix elements based on techniques developed for quantum information purposes. The scheme consists of measuring dispersive and absorptive off-resonant light-ion interactions and is applicable to many atomic species. We determine the dipole matrix element pertaining to the Ca II H line, i.e. the 4$^2$S$_{1/2} \leftrightarrow $ 4$^2$P$_{1/2}$ transition of $^{40}$Ca$^+$, for which we find the value 2.8928(43) ea$_0$. Moreover, the method allows us to deduce the lifetime of the 4$^2$P$_{1/2}$ state to be 6.904(26) ns, which is in agreement with predictions from recent theoretical calculations and resolves a longstanding discrepancy between calculated values and experimental results.