Coherence times of dressed states of a superconducting qubit under extreme driving

TL;DR

This paper investigates the coherence properties of dressed states in a superconducting qubit under intense microwave driving, providing experimental measurements of their energy gaps and decoherence rates.

Contribution

It introduces direct measurement of dressed states in a superconducting qubit with high microwave amplitudes, and compares the results with theoretical predictions.

Findings

Dressed state energy gaps match theoretical models.

Relaxation and dephasing rates of dressed states are quantified.

Dressed states exhibit specific coherence times under extreme driving.

Abstract

In this work, we measure longitudinal dressed states of a superconducting qubit, the single Cooper-pair box, and an intense microwave field. The dressed states represent the hybridization of the qubit and photon degrees of freedom, and appear as avoided level crossings in the combined energy diagram. By embedding the circuit in an rf oscillator, we directly probe the dressed states. We measure their dressed gap as a function of photon number and microwave amplitude, finding good agreement with theory. In addition, we extract the relaxation and dephasing rates of these states.