Fidelity and quantum chaos in the mesoscopic device for the Josephson flux qubit

TL;DR

This paper investigates how a three-junction SQUID device, used as a Josephson flux qubit, can be employed to explore quantum chaos at high energies, analyzing fidelity decay and experimental observability.

Contribution

It demonstrates the potential of a mesoscopic Josephson device to study quantum chaos and calculates fidelity decay regimes under various perturbations.

Findings

Identification of parameter regions for classical chaos

Numerical calculation of fidelity decay regimes

Discussion of experimental observation methods

Abstract

We show that the three-junction SQUID device designed for the Josephson flux qubit can be used to study the dynamics of quantum chaos when operated at high energies. We determine the parameter region where the system is classically chaotic. We calculate numerically the fidelity or Loschmidt echo (LE) in the quantum dynamics under perturbations in the magnetic field and in the critical currents, and study different regimes of the LE. We discuss how the LE could be observed experimentally considering both the preparation of the initial state and the measurement procedure.