Error budget of parametric-resonance gates using a tunable coupler

We study the parametric-resonance gate activated in a system of two transmons coupled via a tunable coupler. Entangling gates such as iSWAP, CZ and fsim can be enacted by modulating one of the qubits through a flux control and using the resulting central band. We employ numerical simulations based on multilevel systems to analyze the performance of the gates as a function of gate duration. We systematically study the error budget of the gate, which is mainly dominated by leakage, ZZ coupling and the decoherence time of the qubits. We explore the dependence of the gate fidelity on several other parameters, such as pulse shape, and coupler flux controls. Other optimal control techniques are also used to design pulses for both the coupler and the qubits, resulting in higher-fidelity gates.