Non-linear dynamics, entanglement and the quantum-classical crossover of two coupled SQUID rings

TL;DR

This paper investigates the quantum-classical transition in two coupled SQUID rings, revealing that entanglement persists even in classical-like trajectories, similar to findings in coupled Duffing oscillators.

Contribution

It extends previous work on coupled Duffing oscillators to more realistic SQUID systems, showing shared entanglement features despite system differences.

Findings

Entanglement persists in classical-like trajectories of SQUID rings.

Differences observed between SQUID and Duffing oscillator behaviors.

Shared feature of entanglement in classical regimes across systems.

Abstract

We explore the quantum-classical crossover of two coupled, identical, superconducting quantum interference device (SQUID) rings. We note that the motivation for this work is based on a study of a similar system comprising two coupled Duffing oscillators. In that work we showed that the entanglement characteristics of chaotic and periodic (entrained) solutions differed significantly and that in the classical limit entanglement was preserved only in the chaotic-like solutions. However, Duffing oscillators are a highly idealised toy model. Motivated by a wish to explore more experimentally realisable systems we now extend our work to an analysis of two coupled SQUID rings. We observe some differences in behaviour between the system that is based on SQUID rings rather than on Duffing oscillators. However, we show that the two systems share a common feature. That is, even when the SQUID ring's trajectories appear to follow (semi) classical orbits entanglement persists.