Quantum Heating of a nonlinear resonator probed by a superconducting   qubit
  We measure the quantum fluctuations of a pumped nonlinear resonator, using a superconducting artificial atom as an in-situ probe. The qubit excitation spectrum gives access to the frequency and temperature of the intracavity field fluctuations. These are found to be in agreement with theoretical predictions; in particular we experimentally observe the phenomenon of quantum heating. 
F. R. Ong, M. Boissonneault, F. Mallet, A. C. Doherty, A. Blais, D.   Vion, D. Esteve, and P. Bertet
quant-ph cond-mat.mes-hall cond-mat.supr-con