Grid-bus surface code architecture

We present a scalable hybrid architecture for the 2D surface code combining superconducting resonators and spin qubits in nanowires with tunable spin-orbit coupling. The back-bone of this architecture is a square lattice of capacitively coupled coplanar waveguide resonators each of which hosts a nanowire spin-orbit qubit. A simple circuit QED model is derived for the coupling between the spin degree of freedom and the quantized resonator modes on the lattice. The electrically tunable qubit frequency allows for fast single qubit phase gates. A two-qubit $\sqrt{i\rm SWAP}$ gate between neighboring qubits can be realized by a third order process, whereby a virtual photon in one cavity is created by a first qubit, coherently transferred to a neighboring cavity, and absorbed by a second qubit in that cavity. Numerical simulations with realistic parameters predict high gate fidelities.