  The ability to engineer high-fidelity gates on quantum processors in the
presence of systematic errors remains the primary barrier to achieving quantum
advantage. Quantum optimal control methods have proven effective in
experimentally realizing high-fidelity gates, but they require exquisite
calibration to be performant. We apply robust trajectory optimization
techniques to suppress gate errors arising from system parameter uncertainty.
We propose a derivative-based approach that maintains computational efficiency
by using forward-mode differentiation. Additionally, the effect of
depolarization on a gate is typically modeled by integrating the Lindblad
master equation, which is computationally expensive. We employ a
computationally efficient model and utilize time-optimal control to achieve
high-fidelity gates in the presence of depolarization. We apply these
techniques to a fluxonium qubit and suppress simulated gate errors due to
parameter uncertainty below $10^{-7}$ for static parameter deviations on the
order of $1\%$.
