Low- and high-frequency noise from coherent two-level systems

TL;DR

This paper investigates how a single ensemble of coherent two-level systems can produce both low- and high-frequency noise in superconducting quantum systems, explaining experimental observations through a specific TLS parameter distribution.

Contribution

It demonstrates that a natural distribution of tunneling TLS parameters can account for the observed correlation between low- and high-frequency noise.

Findings

A log-uniform distribution in tunnel splitting explains noise correlations.

The model reproduces experimental noise power across frequency domains.

TLS ensemble parameters influence noise behavior in quantum systems.

Abstract

Recent experiments indicate a connection between the low- and high-frequency noise affecting superconducting quantum systems. We explore the possibilities that both noises can be produced by one ensemble of microscopic modes, made up, e.g., by sufficiently coherent two-level systems (TLS). This implies a relation between the noise power in different frequency domains, which depends on the distribution of the parameters of the TLSs. We show that a distribution, natural for tunneling TLSs, with a log-uniform distribution in the tunnel splitting and linear distribution in the bias, accounts for experimental observations.