  Minimizing phase and other errors in experimental quantum gates allows higher
fidelity quantum processing. To quantify and correct for phase errors in
particular, we have developed a new experimental metrology --- amplified phase
error (APE) pulses --- that amplifies and helps identify phase errors in
general multi-level qubit architectures. In order to correct for both phase and
amplitude errors specific to virtual transitions and leakage outside of the
qubit manifold, we implement "half derivative" an experimental simplification
of derivative reduction by adiabatic gate (DRAG) control theory. The phase
errors are lowered by about a factor of five using this method to $\sim
1.6^{\circ}$ per gate, and can be tuned to zero. Leakage outside the qubit
manifold, to the qubit $|2\rangle$ state, is also reduced to $\sim 10^{-4}$ for
$20\%$ faster gates.
