  We have observed the spatial interactions between two ultra-weak optical
beams that are initially collinear and non-overlapping. The weak beams are
steered towards each other by a spatially varying cross-Kerr refractive index
waveguide written by a strong laser beam in a three-level atomic medium
utilizing quantum coherence. After being brought together, the weak beams show
controllable phase-dependent outcomes. This is the first observation of
soliton-like interactions between weak beams and can be useful for
all-optically tunable beam-combining, switching and gates for weak photonic
signals.
