  The existence of robust chiral edge states in a finite topologically
nontrivial chern insulator is a consequence of the bulk-boundary
correspondence. In this paper, we present a theoretical framework based on
lattice Green's function to study the scattering of such chiral edge electrons
by a single localized impurity. To this end, in the first step, we consider the
standard topological Haldane model on a honeycomb lattice with strip geometry.
We obtain analytical expressions for the wave functions and their corresponding
energy dispersion of the low-energy chiral states localized at the edge of the
ribbon. Then, we employ the $T$-matrix Lippmann-Schwinger approach to
explicitly show the robustness of chiral edge states against the impurity
scattering. This backscattering-free process has an interesting property that
the transmitted wave function acquires an additional phase factor. Although
this additional phase factor does not affect quantum transport through the
chiral channel it can carry quantum information. As an example of such quantum
information transport, we investigate the entanglement of two magnetic
impurities in a chern insulator through the dissipation-less scattering of
chiral electrons.
