Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic   oscillator
  We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence. 
Simon Gustavsson, Jonas Bylander, Fei Yan, Pol Forn-D\'iaz, Vlad   Bolkhovsky, Danielle Braje, George Fitch, Khalil Harrabi,...
cond-mat.supr-con quant-ph