Pseudo-Rabi oscillations in superconducting flux qubits in the classical regime

TL;DR

This paper demonstrates that classical nonlinear effects in a three-Josephson-junction flux qubit can produce low-frequency oscillations resembling quantum Rabi oscillations, distinguishable by their response to external fields.

Contribution

It reveals that pseudo-Rabi oscillations can occur in classical regimes of flux qubits, expanding understanding of nonlinear effects beyond quantum phenomena.

Findings

Classical flux qubits exhibit low-frequency oscillations under external resonance.

Pseudo-Rabi oscillation frequency scales linearly with external field amplitude.

Oscillations can be induced at multiple harmonics and overtones, not just the resonance frequency.

Abstract

Nonlinear effects in mesoscopic devices can have both quantum and classical origins. We show that a three-Josephson-junction (3JJ) flux qubit in the _classical_ regime can produce low-frequency oscillations in the presence of an external field in resonance with the (high-frequency) harmonic mode of the system, $\omega$. Like in the case of_quantum_ Rabi oscillations, the frequency of these pseudo-Rabi oscillations is much smaller than $\omega$ and scales approximately linearly with the amplitude of the external field. This classical effect can be reliably distinguished from its quantum counterpart because it can be produced by the external perturbation not only at the resonance frequency $\omega$ and its subharmonics ($\omega/n$), but also at its overtones, $n\omega$.