  We theoretically study scanning gate microscopy (SGM) of electron and hole
trajectories in a quantum point contact (QPC) embedded in a
normal-superconductor (NS) junction. At zero voltage bias, the electrons and
holes transported through the QPC form angular lobes and are subject to
self-interference, which marks the SGM conductance maps with interference
fringes analogously as in normal systems. We predict that for an NS junction at
non-zero bias a beating pattern is to occur in the conductance probed with the
use of the SGM technique owing to a mismatch of the Fermi wavevectors of
electrons and holes. Moreover, the SGM technique exposes a pronounced
disturbance in the angular conductance pattern, as the retroreflected hole does
not retrace the electron path due to wavevector difference.
