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

We probe electric-field noise near the 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. The data can be explained by considering noise from fluctuators with a broad distribution of activation energies around 0.5 eV. These energies suggest defect motion as a relevant microscopic mechanism, likely taking place at the metal trap surface. Our results show that high-temperature studies of surface noise are a key to identifying the origin of "anomalous heating" - a major source of ion motional decoherence in surface traps that limits their performance as quantum devices.