Probing the quantum fluctuations of a non linear resonator with a superconducting qubit

Denis Vion 

co-authors: F.R. Ong (1), M. Boissonneault (2), F. Mallet(1), A. Palacios-Laloy (1), A. Dewes (1), P. Bertet (1), D. Vion (1), D. Esteve (2), A. Blais (2), and A. Doherty (3) 

(1) CEA-Saclay, Gif-sur-Yvette, France
(2) Departement de Physique, Universite de Sherbrooke, Sherbrooke, Quebec, Canada
(3) School of Physics, The University of Sydney, Sydney, Australia

We experimentally investigate the quantum fluctuations of a pumped nonlinear resonator, using a superconducting articial atom (transmon) to which it is coupled as a probe. In that purpose we excite sideband transitions in which the qubit effectively heats up or cools down the nonlinear resonator dressed by the pump photons. The frequency of these transitions gives access to the dressed resonator
frequency. The relative height of the two peaks yields an absolute measurement of the effective field temperature, which is found to be in agreement with theoretical predictions thus bringing an experimental support to the phenomenon of quantum heating.