  A scheme for generating an entangled state in a two spin-1/2 system by means
of a spin-dependent potential scattering of another qubit is presented and
analyzed in three dimensions. The entanglement is evaluated in terms of the
concurrence both at the lowest and in full order in perturbation with an
appropriate renormalization for the latter, and its characteristics are
discussed in the context of (in)distinguishability of alternative paths for a
quantum particle.
