Interband transitions and interference effects in superconducting qubits

TL;DR

This paper explores phase-sensitive interference effects in a driven superconducting qubit system, revealing multiphoton transitions and interference phenomena analogous to molecular vibronic transitions, with implications for quantum control.

Contribution

It introduces a detailed analysis of multiphoton and vibronic-like interference effects in superconducting qubits driven by periodic signals, connecting quantum optics concepts with superconducting circuit physics.

Findings

Identification of two types of multiphoton transitions.

Observation of interference effects analogous to molecular vibronic transitions.

Application of Landau-Zener and Franck-Condon models to superconducting qubits.

Abstract

We investigate phase-sensitive interference effects in a periodically $\sin(2\pi f_{\rm rf} t)$-driven, artificial two-state system connected to a microwave resonator at $f_{LC} \simeq 800$ MHz. We observe two kinds of multiphoton transitions in the two-state system, accompanied by: 1) Several quanta from the drive at $f_{\rm rf}$ and 2) one quantum at $f_{\rm rf}$ and several at $f_{LC}$. The former are described using phase-sensitive Landau-Zener transitions, while the latter are discussed in terms of vibronic transitions in diatomic molecules. Interference effects in the vibronic transitions governed by Franck-Condon coefficients are also considered.