Observation of Autler-Townes effect in a dispersively dressed Jaynes-Cummings system

TL;DR

This paper reports the observation of the Autler-Townes effect in a dispersively dressed Jaynes-Cummings system, demonstrating photon number splitting and spectral splitting due to thermal photons in a superconducting qubit-resonator setup.

Contribution

It provides the first experimental observation of Autler-Townes splitting in a dispersively dressed Jaynes-Cummings system with thermal photons.

Findings

Photon number splitting observed in the qubit spectrum.

Autler-Townes splitting detected in thermal photon peaks.

Theoretical model accurately explains the observed spectral features.

Abstract

Photon number splitting is observed in a transmon coupled to a superconducting quasi-lumped-element resonator in the strong dispersive limit. A thermal population of 5.474 GHz photons at an effective resonator temperature of T = 120mK results in a weak n = 1 photon peak along with the n = 0 photon peak in the qubit spectrum in the absence of a coherent drive on the resonator. Two-tone spectroscopy using independent coupler and probe tones reveals an Autler-Townes splitting in the thermal n = 1 photon peak. The observed effect is explained accurately using the four lowest levels of the dispersively dressed qubit-resonator system and compared to results from numerical simulations of the steady-state master equation for the coupled system.