Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator

TL;DR

This paper explores the driven behavior of a superconducting flux qubit coupled to a microwave resonator, revealing how off-resonant driving influences qubit dynamics and coherence, and demonstrating noise mitigation via rotary-echo sequences.

Contribution

It introduces a detailed analysis of driven qubit-resonator systems, highlighting the impact of off-resonant driving and noise mitigation techniques in superconducting qubits.

Findings

Off-resonant driving modifies the qubit Rabi frequency.

Low-frequency noise reduces coherence time during driven evolution.

Rotary-echo sequences effectively mitigate noise effects.

Abstract

We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.