Superconducting qubits with adjustable coupling, Part II: Fast two-qubit gates

The g-mon architecture combines high coherence Xmon qubits with fast tunable coupling. In this work, we demonstrate the advantages of tunable coupling to high fidelity single and two-qubit gates. By suppressing the qubit-qubit interaction, we are able to achieve high-fidelity simultaneous single qubit operations without the need for substantial detuning. Turning on the qubit-qubit interaction allows for a fast two-qubit controlled Z with gate times less than 30 ns. By eliminating the frequency crowding issues associated with static coupling and achieving two-qubit gate times approaching that of single qubit operations, the g-mon architecture is a promising system for scalable quantum computation.