Evidence for multiple mechanisms underlying surface electric-field noise in ion traps

TL;DR

This study investigates the temperature dependence of surface electric-field noise in ion traps, revealing multiple underlying mechanisms that change after ion milling, with implications for improving quantum information processing and precision measurements.

Contribution

It demonstrates that ion milling alters the temperature scaling of electric-field noise, indicating multiple noise mechanisms and material-dependent behaviors in ion trap electrodes.

Findings

Temperature scaling changes from power-law to Arrhenius after ion milling.

Noise mechanisms differ before and after ion milling.

Frequency and distance dependencies remain unchanged by ion milling.

Abstract

Electric-field noise from ion-trap electrode surfaces can limit the fidelity of multiqubit entangling operations in trapped-ion quantum information processors and can give rise to systematic errors in trapped-ion optical clocks. The underlying mechanism for this noise is unknown, but it has been shown that the noise amplitude can be reduced by energetic ion bombardment, or "ion milling," of the trap electrode surfaces. Using a single trapped $^{88}$Sr$^{+}$ ion as a sensor, we investigate the temperature dependence of this noise both before and after ex situ ion milling of the trap electrodes. Making measurements over a trap electrode temperature range of 4 K to 295 K in both sputtered niobium and electroplated gold traps, we see a marked change in the temperature scaling of the electric-field noise after ion milling: power-law behavior in untreated surfaces is transformed to Arrhenius behavior after treatment. The temperature scaling becomes material-dependent after treatment as well, strongly suggesting that different noise mechanisms are at work before and after ion milling. To constrain potential noise mechanisms, we measure the frequency dependence of the electric-field noise, as well as its dependence on ion-electrode distance, for niobium traps at room temperature both before and after ion milling. These scalings are unchanged by ion milling.