Electric-field noise from carbon-adatom diffusion on a Au(110) surface: first-principles calculations and experiments

TL;DR

This study combines first-principles calculations and experiments to identify carbon adatom diffusion on Au(110) surfaces as a source of electric-field noise affecting trapped-ion quantum gate coherence.

Contribution

It provides a detailed theoretical and experimental analysis linking adatom diffusion and dipole fluctuations to electric-field noise in ion traps.

Findings

Diffusion of carbon adatoms alters the energy landscape on Au(110).

Dipole moment variations due to diffusion reproduce measured noise spectra.

Estimated noise spectral density aligns with experimental data.

Abstract

The decoherence of trapped-ion quantum gates due to heating of their motional modes is a fundamental science and engineering problem. This heating is attributed to electric-field noise arising from the trap-electrode surfaces. In this work, we investigate the source of this noise by focusing on the diffusion of carbon-containing adsorbates on the surface of Au(110). We show by density functional theory, based on detailed scanning probe microscopy, how the carbon adatom diffusion on the gold surface changes the energy landscape, and how the adatom dipole moment varies with the diffusive motion. A simple model for the diffusion noise, which varies quadratically with the variation of the dipole moment, qualitatively reproduces the measured noise spectrum, and the estimate of the noise spectral density is in accord with measured values.