Dephasing of solid-state qubits at optimal points

TL;DR

This paper investigates how different noise sources, especially nonlinear 1/f and Ohmic noise, affect the decoherence of solid-state qubits at optimal points where linear noise coupling is minimized.

Contribution

It provides a detailed analysis of nonlinear noise effects on qubit decoherence, extending understanding beyond linear coupling models.

Findings

Higher-order effects significantly influence qubit evolution under 1/f noise

Optimal points suppress linear noise coupling but nonlinear effects remain impactful

Nonlinear noise sources can dominate decoherence in certain regimes

Abstract

Motivated by recent experiments with Josephson-junction circuits, we analyze the influence of various noise sources on the dynamics of two-level systems at optimal operation points where the linear coupling to low-frequency fluctuations is suppressed. We study the decoherence due to nonlinear (quadratic) coupling, focusing on the experimentally relevant 1/f and Ohmic noise power spectra. For 1/f noise strong higher-order effects influence the evolution.