Event Details

Suppression of low-frequency charge noise in quantum devices by surface spin desorption

Abstract: Reducing noise and decoherence in solid state quantum devices will enable enhanced performance of a wide range of sensors and circuits, however, such efforts have so far been largely inhibited by the lack of knowledge about the origin of this noise and decoherence. We correlate measurements of frequency (dielectric) noise and loss in superconducting resonators made from NbN on sapphire with ultrasensitive in-situ electron spin resonance (ESR) measurements on the same devices. We find that after removing a large fraction of surface spins by a simple heat treatment, the magnitude of the dielectric noise is reduced by almost 10 times. Our data is in excellent agreement with a model for strongly interacting two-level systems, allowing us to attribute the origin of the dielectric noise to ESR-active slow two-level charge fluctuators on the surface of our devices. Here we show that surface spins directly affect the performance of high-Q superconducting resonators, but the chemical fingerprint of the ESR spectrum together with noise and loss data enables a whole new route to identifying the origin of noise in quantum circuits.