Electric-field noise from thermally-activated fluctuators in a surface ion trap

Electric-field noise originating from surfaces is a major source of motional decoherence in ion trap chips. A better understanding of this noise is important for the fabrication of low-noise quantum devices. We probe electric-field noise near the aluminum-copper surface of an ion trap chip in a previously unexplored high-temperature regime. A saturation of the noise amplitude occurs around 500 K, which, together with a small change in the frequency scaling, points to thermally activated two-state fluctuators as the origin of the noise. We find intriguing similarities in the distribution of activation energies extracted from our data and corresponding data from resistance fluctuation measurements for polycrystalline aluminum films. These similarities suggest atomic motion as a relevant microscopic mechanism, likely taking place at the metal trap surface.