We have created a quantum three-level ladder system with the cavity dispersive energy level in a superconducting circuit quantum electrodynamics system consisting of a transmon qubit and a cavity, and have directly observed the Autler-Townes splitting effect instead of representing it by the probability of the qubit being at each level. A coupler tone is applied on the transition between the second excited state of transmon and cavity dispersive level, while the cavity spectrum is probed. A doublet transmission and anormalous dispersion spectrum of the cavity level is clearly shown. The inverse Fourier transform of cavity spectrum indicates that there is a quantum coherence Rabi oscillation of the populations between cavity and qubit.
@article{arxiv.1604.03663,
title = {Quantum coherence between cavity and artificial atom in a superconducting circuit QED ladder system},
author = {Qichun Liu and Han Cai and Yingshan Zhang and Jianshe Liu and Wei Chen},
journal= {arXiv preprint arXiv:1604.03663},
year = {2016}
}