Noise Properties of Superconducting Coplanar Waveguide Microwave Resonators

TL;DR

This paper investigates phase noise in superconducting coplanar waveguide resonators, finding it dominates amplitude noise and is likely caused by two-level systems in dielectric materials, impacting device readouts.

Contribution

It provides the first detailed measurement of phase noise in these resonators and links it to two-level systems, offering insights for improving quantum device performance.

Findings

Phase noise dominates over amplitude noise by over 30 dB.

Noise manifests as resonance frequency jitter, not amplitude fluctuations.

Two-level systems in dielectrics are likely responsible for phase noise.

Abstract

We have measured noise in thin-film superconducting coplanar waveguide resonators. This noise appears entirely as phase noise, equivalent to a jitter of the resonance frequency. In contrast, amplitude fluctuations are not observed at the sensitivity of our measurement. The ratio between the noise power in the phase and amplitude directions is large, in excess of 30 dB. These results have important implications for resonant readouts of various devices such as detectors, amplifiers, and qubits. We suggest that the phase noise is due to two-level systems in dielectric materials.