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.
@article{arxiv.cond-mat/0412668,
title = {Low- and high-frequency noise from coherent two-level systems},
author = {Alexander Shnirman and Gerd Schön and Ivar Martin and Yuriy Makhlin},
journal= {arXiv preprint arXiv:cond-mat/0412668},
year = {2007}
}