Quantum and Classical Chirps in an Anharmonic Oscillator
  We measure the state dynamics of a tunable anharmonic quantum system, the Josephson phase circuit, under the excitation of a frequency-chirped drive. At small anharmonicity, the state evolves like a wavepacket - a characteristic response in classical oscillators; in this regime we report exponentially enhanced lifetimes of highly excited states, held by the drive. At large anharmonicity, we observe sharp steps, corresponding to the excitation of discrete energy levels. The continuous transition between the two regimes is mapped by measuring the threshold of these two effects. 
Yoni Shalibo, Ya'ara Rofe, Ido Barth, Lazar Friedland, Radoslaw   Bialczack, John M. Martinis and Nadav Katz
quant-ph cond-mat.supr-con