Driven Dynamics and Rotary Echo of a Qubit Tunably Coupled to a Harmonic Oscillator

We have investigated the driven dynamics of a superconducting flux qubitthat is tunably coupled to a microwave resonator. We find that the qubitexperiences 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 parametercauses a reduction of the coherence timeduring driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.