Charge qubit driven via the Josephson nonlinearity

TL;DR

This paper investigates nonlinear effects in a charge qubit driven by strong microwave flux, revealing limitations of traditional models and providing experimental insights into quasienergy levels using cavity probing.

Contribution

It introduces a detailed analysis of nonlinear phenomena in driven charge qubits, combining theoretical modeling with experimental validation using cavity spectroscopy.

Findings

Linear Landau-Zener-Stückelberg model is inadequate for periodic systems with multiple crossings.

Experimental probing of quasienergy levels aligns well with numerical simulations.

Nonlinear effects significantly influence the qubit dynamics under strong driving.

Abstract

We study the novel nonlinear phenomena that emerge in a charge qubit due to the interplay between a strong microwave flux drive and a periodic Josephson potential. We first analyze the system in terms of the linear Landau-Zener-St\"uckelberg model, and show its inadequacy in a periodic system with several Landau-Zener crossings within a drive period. Experimentally, we probe the quasienergy levels of the driven qubit with an LC-cavity, which requires the use of linear response theory. We also show that our numerical calculations are in good agreement with the experimental data.