Multi-Transmon circuit QED using local and fast flux biasing

We report local and fast flux tuning of Transmon qubits in circuit QED by means of proximal short-circuited coplanar waveguides. We characterize the effect of these additional microwave channels on qubit lifetime. We demonstrate one-qubit $Z$-gates and time-domain control of two-qubit interaction via virtual photon exchange. Gate performance is characterized by process tomography and compared to gating by AC Stark shift as previously investigated by the Yale cQED team [1]. Research supported by NSF, NSA and ARO. [1] Majer \textit{et al.,} \textit{Nature} \textbf{449}, 443 (2007).