A Fully Quantum Mechanical Model of a SQUID Ring Coupled to an Electromagnetic Field

TL;DR

This paper develops a fully quantum mechanical model of a SQUID ring coupled to an electromagnetic field, analyzing energy exchange, entanglement, and control via magnetic flux, and compares it with a semi-classical approximation.

Contribution

It introduces a comprehensive quantum model of a SQUID-electromagnetic system and compares quantum and semi-classical descriptions, highlighting conditions for strong coupling and entanglement.

Findings

Energy exchange occurs between modes.

System becomes entangled under certain flux conditions.

Quantum and semi-classical models show different dynamics.

Abstract

A quantum system comprising of a monochromatic electromagnetic field coupled to a SQUID ring with sinusoidal non-linearity, is studied. A magnetostatic flux $\Phi_{x}$ is also threading the SQUID ring, and is used to control the coupling between the two systems. It is shown that for special values of $\Phi_{x}$ the system is strongly coupled. The time evolution of the system is studied. It is shown that exchange of energy takes place between the two modes and that the system becomes entangled. A second quasi-classical model that treats the electromagnetic field classically is also studied. A comparison between the fully quantum mechanical model with the electromagnetic field initially in a coherent state and the quasi-classical model, is made.