Robustness of quantum gates with hybrid spin-photon qubits in superconducting resonators

We discuss a scalable scheme for the implementation of quantum-information processing in qubits formed by superconducting resonators and spin ensembles. The scheme is based on a hybrid dual-rail encoding, which allows one to perform both single- and two-qubit gates by shifting the resonator frequency. We estimate the quantum-gate fidelity by simulating the driven dynamics through a master-equation approach. High values of the fidelity can be achieved also in the presence of the main decoherence sources, namely, cavity-photon loss, and pure dephasing of the superconductive elements that are involved in the two-qubit gates. This result allows envisioning the scalability of such elements to a quantum-computing architecture made of an array of hybrid spin-photon qubits. Analogous results are obtained for a simpler, nonscalable setup, which we propose here in order to simplify the realization of the first proof-of-principle experiments.