  We discover and characterize strong quantum scars, or eigenstates resembling
classical periodic orbits, in two-dimensional quantum wells perturbed by local
impurities. These scars are not explained by ordinary scar theory, which would
require the existence of short, moderately unstable periodic orbits in the
perturbed system. Instead, they are supported by classical resonances in the
unperturbed system and the resulting quantum near-degeneracy. Even in the case
of a large number of randomly scattered impurities, the scars prefer distinct
orientations that extremize the overlap with the impurities. We demonstrate
that these preferred orientations can be used for highly efficient transport of
quantum wave packets across the perturbed potential landscape. Assisted by the
scars, wave-packet recurrences are significantly stronger than in the
unperturbed system. Together with the controllability of the preferred
orientations, this property may be very useful for quantum transport
applications.
