Reducing TLS losses in superconducting circuits using solid neon

Electrons levitating above the surface of solid neon have emerged as a promising platform for high quality qubits [1]. The quality of the neon crystal in these systems is crucial for qubit performance and scalability. We report on the controlled growth and characterization of thin solid neon films using multiplexed superconducting CPW resonators by monitoring changes in the resonant frequency and internal quality factor (Qi). We find that annealing the sample at 12K improves the uniformity of neon growth. Surprisingly, we observe an increase in Qi of the resonators that persists even after the neon is removed. Through repeated neon depositions, we measured up to a 3 x increase in Qi at the single photon limit, and more than an order of magnitude increase in Qi at high power. Comparing resonators with different geometries as a function of microwave power and temperature, we attribute these improvements to desorption of two-level fluctuators from the superconductor surface.

References

[1] X. Zhou et al. (2022). Single electrons on solid neon as a solid-state qubit platform. Nature, 605(7908), 46–50.