  We consider scanning gate microscopy imaging of the double slit interference
for a pair of quantum point contacts (QPCs) defined within the two-dimensional
electron gas. The interference is clearly present in the scattered electron
wave functions for each of the incident subbands. Nevertheless, we find that
the interference is generally missing in the experimentally accessible
conductance maps for many incident subbands. We explain this finding on the
basis of the Landauer approach.
  A setup geometry allowing for observation of the double slit interference by
the scanning gate microscopy is proposed.
