Quantum chaos in the mesoscopic device for the Josephson flux qubit

TL;DR

This paper demonstrates that a three-junction SQUID device used as a Josephson flux qubit can exhibit quantum chaos at high energies, with spectral statistics aligning with classical chaos measures.

Contribution

It introduces the use of a Josephson flux qubit device to study quantum chaos through spectral analysis and phase space representations.

Findings

Spectral statistics fit Berry Robnik theory

Wave functions localize on classical structures

System exhibits quantum chaos at high energies

Abstract

We show that the three-junction SQUID device designed for the Josephson flux qubit can be used to study quantum chaos when operated at high energies. In the parameter region where the system is classically chaotic we analyze the spectral statistics. The nearest neighbor distributions $P(s)$ are well fitted by the Berry Robnik theory employing as free parameters the pure classical measures of the chaotic and regular regions of phase space in the different energy regions. The phase space representation of the wave functions is obtained via the Husimi distributions and the localization of the states on classical structures is analyzed.