Co-design of quantum devices with optimal control*

The practical application of quantum computing and the research into qubit and device designs are often separate fields. When exploring operating regimes for quantum devices, often specific properties like noise resistance are selected based on previous experience or intuition, resulting in designs like the Transmon and the Fluxonium. In the current NISQ era, there is a demand for functional quantum devices to solve relevant computational problems, which motivates a more utilitarian perspective on device design: The goal is to have a device that is employed to run a given algorithm with state-of-the-art performance.

    In this work, we assume this perspective and use optimal control tools to derive the gates required by an algorithm and, in tandem, explore the model space of superconducting quantum computer design to maximize gate fidelity. We investigate candidate designs for two-qubit devices: a tunable coupler setup, tunable qubits with static coupling and fixed qubits with fixed couplings. For each design, we optimize properties like qubit frequencies, anharmonicities and coupling strengths for the best performance of both local and entangling gates and investigate applications where one of the designs outperforms the others.