  Motivated by recent experimental research, we study the processes in an ac
driven superconducting constriction whereby one quasiparticle is promoted to
the delocalized states outside the superconducting gap. We demonstrate that
with these processes one can control the population of the Andreev bound states
in the constriction. We stress an interesting charge asymmetry of these
processes that may produce a charge imbalance of accumulated quasiparticles,
which depends on the phase.
