Single-photon-driven high-order sideband transitions in an ultrastrongly coupled circuit-quantum-electrodynamics system
Zhen Chen, Yimin Wang, Tiefu Li, Lin Tian, Yueyin Qiu, K. Inomata, Fumiki Yoshihara, Siyuan Han, Franco Nori, J. S. Tsai, J. Q. You · Physical Review A · 2017
We report the experimental observation of high-order sideband transitions at the single-photon level in a quantum circuit system of a flux qubit ultrastrongly coupled to a coplanar waveguide resonator. With the coupling strength reaching 10% of the resonator's fundamental frequency, we obtain clear signatures of higher order red-sideband and first-order blue-sideband transitions, which are mainly due to the ultrastrong Rabi coupling. Our observation advances the understanding of ultrastrongly coupled systems and paves the way to study high-order processes in the quantum Rabi model at the single-photon level.