Coupling Two Spin Qubits with a High-Impedance Resonator

Fast, high-fidelity single and two-qubit gates are essential to building a viable quantum information processor, but achieving both in the same system has proved challenging for spin qubits. In this talk, I will propose an approach to perform a two-qubit controlled phase gate between two singlet-triplet qubits using an electromagnetic resonator. We use the longitudinal coupling of the qubits to the resonator to devise a gate relying on a single tone applied to the qubits near the resonator's frequency that is independent of the qubits' splitting. By using high impedance resonators, we predict an increase in two-qubit gate speed of up to two orders of magnitude. Simulations show average gate fidelities of over 96% using currently achievable experimental parameters and over 99.5% using state-of-the-art resonator technology. By optimizing the gate fidelity in terms of parameters tuneable in-situ, we find that it takes a simple power-law form in terms of the resonator's impedance and quality and the qubits' noise bath. I will also discuss our experimental progress towards implementing this gate.