Classical analogs for Rabi-oscillations, Ramsey-fringes, and spin-echo in Josephson junctions

TL;DR

This paper demonstrates that phenomena like Rabi-oscillations, Ramsey-fringes, and spin-echo in Josephson junctions can be explained by classical nonlinear dynamics, challenging their exclusive quantum interpretation.

Contribution

The study shows that classical models can replicate key quantum-like behaviors in Josephson circuits, providing alternative explanations for experimental observations.

Findings

Classical nonlinear dynamics reproduce Rabi-oscillations.

Ramsey-fringes and spin-echo explained classically.

Quantum phenomena may have classical analogs in Josephson circuits.

Abstract

We investigate the results of recently published experiments on the quantum behavior of Josephson circuits in terms of the classical modelling based on the resistively and capacitively-shunted (RCSJ) junction model. Our analysis shows evidence for a close analogy between the nonlinear behavior of a pulsed microwave-driven Josephson junction at low temperature and low dissipation and the experimental observations reported for the Josephson circuits. Specifically, we demonstrate that Rabi-oscillations, Ramsey-fringes, and spin-echo observations are not phenomena with a unique quantum interpretation. In fact, they are natural consequences of transients to phase-locking in classical nonlinear dynamics and can be observed in a purely classical model of a Josephson junction when the experimental recipe for the application of microwaves is followed and the experimental detection scheme followed. We therefore conclude that classical nonlinear dynamics can contribute to the understanding of relevant experimental observations of Josephson response to various microwave perturbations at very low temperature and low dissipation.