Decoherence from ensembles of two-level fluctuators

TL;DR

This paper investigates how ensembles of two-level fluctuators cause 1/f noise in Josephson qubits, focusing on the statistical properties and self-averaging behavior of the resulting dephasing noise.

Contribution

It analyzes the dephasing process for various distribution functions of fluctuators and explores the conditions under which the noise is Gaussian or non-Gaussian.

Findings

Non-Gaussian noise arises with power-law distributed coupling strengths.

Self-averaging properties depend on the distribution tail behavior.

Results inform understanding of qubit decoherence mechanisms.

Abstract

1/f noise, the major source of dephasing in Josephson qubits, may be produced by an ensemble of two-level systems. Depending on the statistical properties of their distribution, the noise distribution can be Gaussian or non-Gaussian. The latter situation is realized, for instance, when the distribution of coupling strengths has a slowly decaying power-law tail. In this regime questions of self-averaging and sample-to-sample fluctuations become crucial. We study the dephasing process for a class of distribution functions and analyze the self-averaging properties of the results.