A Classical Analysis of Capacitively Coupled Superconducting Qubits

TL;DR

This paper demonstrates that the phenomena observed in capacitively coupled superconducting qubits, previously attributed to quantum entanglement, can be explained entirely through classical circuit analysis using the RSCJ model.

Contribution

It provides a classical analysis of a superconducting qubit system, challenging the assumption that observed correlations necessarily imply quantum entanglement.

Findings

Classical RSCJ model reproduces experimental observations

Transient dynamics explain correlated states

Quantum entanglement is not the only explanation

Abstract

An electrical circuit consisting of two capacitively coupled inductive loops, each interrupted by a Josephson junction, is analyzed through the classical RSCJ model. The same circuit has recently been studied experimentally and the results were used to demonstrate quantum mechanical entanglement in the system by observing the correlated states of the two inductive loops after initial microwave perturbations. Our classical analysis shows that the observed phenomenon exists entirely within the classical RSCJ model, and we provide a detailed intuitive description of the transient dynamics responsible for the observations.