Electric-Field Noise above a Thin Dielectric Layer on Metal Electrodes

TL;DR

This paper models how a thin dielectric layer on metal electrodes significantly increases electric-field noise, affecting ion trap performance by altering noise magnitude and frequency dependence.

Contribution

It provides a quantitative analysis of electric-field noise enhancement due to dielectric layers, highlighting the importance for ion trap decoherence mitigation.

Findings

Dielectric layers increase noise proportionally to their thickness.

Electric field noise varies with the inverse fourth power of distance.

Dielectric layers induce frequency-dependent noise scaling inversely with frequency.

Abstract

The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electric-field noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps.