  Recent work on Ising-coupled double-quantum-dot spin qubits in GaAs with
voltage-controlled exchange interaction has shown improved two-qubit gate
fidelities from the application of oscillating exchange along with a strong
magnetic field gradient between adjacent dots. By examining how noise
propagates in the time-evolution operator of the system, we find an optimal set
of parameters that provide passive stroboscopic circumvention of errors in
two-qubit gates to first order. We predict over 99% two-qubit gate fidelities
in the presence of quasistatic and 1/$\textit{f}$ noise, which is an order of
magnitude improvement over the typical unoptimized implementation.
