Non-Gaussian low-frequency noise as a source of qubit decoherence

TL;DR

This paper investigates how non-Gaussian low-frequency noise from bistable fluctuators causes qubit decoherence, revealing distinct echo signal behaviors and deviations from Gaussian models, especially at strong coupling.

Contribution

It provides an exact analysis of qubit decoherence due to a single bistable fluctuator and explores the effects of multiple fluctuators on echo signals, highlighting non-Gaussian noise impacts.

Findings

Echo signal exhibits plateaus related to fluctuator parameters.

Decoherence behavior deviates from Gaussian models at strong coupling.

Multiple fluctuators lead to different decoherence dynamics than single fluctuator.

Abstract

We study decoherence in a qubit with the distance between the two levels affected by random flips of bistable fluctuators. For the case of a single fluctuator we evaluate explicitly an exact expression for the phase-memory decay in the echo experiment with a resonant ac excitation. The echo signal as a function of time shows a sequence of plateaus. The position and the height of the plateaus can be used to extract the fluctuator switching rate \gamma and its coupling strength v. At small times the logarithm of the echo signal is proportional to t^3. The plateaus disappear when the decoherence is induced by many fluctuators. In this case the echo signal depends on the distribution of the fluctuators parameters. According to our analysis, the results significantly deviate from those obtained in the Gaussian model as soon as v greater than \gamma.