Coherent control of a transmon qubit with a nanowire-based Josephson junction

Transmon qubits\footnote{Koch, J. et al. \textit{Phys. Rev. A} \textbf{76}, 042319 (2007)} have taken great leaps towards realizing a quantum processor\footnote{Barends, R. et al. \textit{Nature} \textbf{508}, 500 (2014)}. Here we present measurements on a novel, gateable transmon. By tuning the electron density in a semiconducting nanowire\footnote{Krogstrup, P. et al. \textit{Nature Materials}, In press} Josephson junction\footnote{Doh, Y. J. et al. \textit{Science} \textbf{309}, 272 (2005)} we can control the qubit frequency from $\sim$3~GHz to $\sim$8~GHz. The transmon was embedded into an aluminum coplanar waveguide cavity for readout and qubit control. In the resonant regime we observe strong cavity-qubit coupling. In the dispersive regime we demonstrate coherent control on the Bloch sphere. The life- and coherence times were measured to $T_2^{*}\! \sim \!2T_1 \!\sim \!1~\mu$s. The coherence time was measured to almost 1$\mu$s. Fast gate operations facilitate z-rotations as well as promising fast two-qubit operations in future multiple-qubit devices. These measurements open new possibilities for gateable superconducting qubits and promise a plausible system for Majorana hybrid devices.