Direct Wigner tomography of a superconducting anharmonic oscillator
  The analysis of wave-packet dynamics may be greatly simplified when viewed in phase-space. While harmonic oscillators are often used as a convenient platform to study wave-packets, arbitrary state preparation in these systems is more challenging. Here, we demonstrate a direct measurement of the Wigner distribution of complex photon states in an anharmonic oscillator - a superconducting phase circuit, biased in the small anharmonicity regime. We test our method on both non-classical states composed of two energy eigenstates and on the dynamics of a phase-locked wavepacket. This method requires a simple calibration, and is easily applicable in our system out to the fifth level. 
Yoni Shalibo, Roy Resh, Ofer Fogel, David Shwa, Radoslaw Bialczak,   John M. Martinis, Nadav Katz
quant-ph cond-mat.supr-con