Dephasing due to nonstationary 1/f noise

TL;DR

This paper introduces a phenomenological model for nonstationary 1/f noise caused by interacting defects, highlighting its impact on qubit dephasing and predicting time-dependent effects in various regimes.

Contribution

It presents a new model capturing non-Gaussian, nonstationary 1/f noise from collective defect excitations affecting Josephson qubits.

Findings

Nonstationary 1/f noise exhibits non-Gaussian features at low temperatures.

Dephasing shows absolute time dependence in strong coupling regimes.

Critical coupling varies with time, affecting qubit coherence.

Abstract

Motivated by recent experiments with Josephson qubits we propose a new phenomenological model for 1/f noise due to collective excitations of interacting defects in the qubit's environment. At very low temperatures the effective dynamics of these collective modes are very slow leading to pronounced non-Gaussian features and nonstationarity of the noise. We analyze the influence of this noise on the dynamics of a qubit in various regimes and at different operation points. Remarkable predictions are absolute time dependences of a critical coupling and of dephasing in the strong coupling regime.