Calibration methods for numerically optimized gates: Part II

Abstract

Applying the techniques of optimal control theory to the design of high-fidelity quantum gates typically requires that the Hamiltonian used to model the system be highly accurate. However, unavoidable inaccuracies in the Hamiltonians used to model superconducting qubits (and their environments) make the direct application of optimal control theory to superconducting qubits particularly challenging. As a result, achieving high-fidelity quantum operations requires that the resulting gate be further "tuned up" or tailored to a specific quantum device through closed-loop experimental calibration. The high-dimensional pulse representations typically used for numerical gate design then become an obstacle to fast calibration; in Ref. [1], for instance, calibrating all 55 pulse parameters required approximately 25 hours. With the goal of systematically addressing this problem, we explore a new method for calibrating numerically optimized pulses and demonstrate the application of this procedure to the calibration of single qubit gates. [1] M. Werninghaus et al., npj Quantum Information 7, 14 (2021).