  We investigate the propagation of a single photon under conditions of
electromagnetically induced transparency in two parallel one-dimensional atomic
clouds which are coupled via Rydberg dipole-dipole interaction. Initially the
system is prepared with a single delocalized Rydberg excitation shared between
the two ensembles and the photon enters both of them in an arbitrary
path-superposition state. By properly aligning the transition dipoles of the
atoms of each cloud we show that the photon can be partially transferred from
one cloud to the other via the dipole-dipole interaction. This coupling leads
to the formation of dark and bright superpositions of the light which
experience different absorption and dispersion. We show that this feature can
be exploited to filter the incident photon in such a way that only a desired
path-superposition state is transmitted transparently. Finally, we generalize
the analysis to the case of N coupled one-dimensional clouds. We show that
within some approximations the dynamics of the propagating photon can be mapped
on that of a free particle with complex mass.
