  We study diffusive shock acceleration (DSA) of electrons in non-relativistic
quasi-perpendicular shocks using self-consistent one-dimensional
particle-in-cell (PIC) simulations. By exploring the parameter space of sonic
and Alfv\'{e}nic Mach numbers we find that high Mach number quasi-perpendicular
shocks can efficiently accelerate electrons to power-law downstream spectra
with slopes consistent with DSA prediction. Electrons are reflected by magnetic
mirroring at the shock and drive non-resonant waves in the upstream. Reflected
electrons are trapped between the shock front and upstream waves and undergo
multiple cycles of shock drift acceleration before the injection into DSA.
Strong current-driven waves also temporarily change the shock obliquity and
cause mild proton pre-acceleration even in quasi-perpendicular shocks, which
otherwise do not accelerate protons. These results can be used to understand
nonthermal emission in supernova remnants and intracluster medium in galaxy
clusters.
