Trapped-ion probing of light-induced charging effects on dielectrics

TL;DR

This study uses trapped calcium ions to precisely measure how light-induced charging on dielectric surfaces affects ion trap potentials, revealing charge sensitivities and implications for miniaturized quantum devices.

Contribution

It introduces a method to quantify light-induced charging effects on dielectrics using trapped ions, with detailed characterization of electric field perturbations.

Findings

Sensitive detection of as few as 40 elementary charges per √Hz.

Charging effects observed with light wavelengths up to 729 nm.

Implications for material choice and optics in miniaturized ion traps.

Abstract

We use a string of confined $^{40}$Ca$^+$ ions to measure perturbations to a trapping potential which are caused by light-induced charging of an anti-reflection coated window and of insulating patches on the ion-trap electrodes. The electric fields induced at the ions' position are characterised as a function of distance to the dielectric, and as a function of the incident optical power and wavelength. The measurement of the ion-string position is sensitive to as few as $40$ elementary charges per $\sqrt{\mathrm{Hz}}$ on the dielectric at distances of order millimetres, and perturbations are observed for illumination with light of wavelengths as long as 729\,nm. This has important implications for the future of miniaturised ion-trap experiments, notably with regards to the choice of electrode material, and the optics that must be integrated in the vicinity of the ion. The method presented can be readily applied to the investigation of charging effects beyond the context of ion trap experiments.