  We study graphene quantum point contacts (QPC) and imaging of the
backscattering of the Fermi level wave function by potential introduced by a
scanning probe. We consider both etched single-layer QPCs as well as the ones
formed by bilayer patches deposited at the sides of the monolayer conducting
channel using an atomistic tight binding approach. A computational method is
developed to effectively simulate an infinite graphene plane outside the QPC
using a computational box of a finite size. We demonstrate that in spite of the
Klein phenomenon interference due to the backscattering at a circular n-p
junction induced by the probe potential is visible in spatial maps of
conductance as functions of the probe position.
