  We present an entanglement swapping process for unknown nonmaximally
entangled photonic states, where the standard Bell-state measurement is
replaced by a three-step quantum walk-like state discrimination process, i.e.,
the practically nontrivial coupling element of two photons is replaced by
manipulating their trajectories, which will greatly enrich the dynamics of the
coupling between photons in realizing quantum computation, and reduce the
integration complexity of optical quantum processing. In addition, the output
state can be maximally entangled, which allows for entanglement concentration
as well.
