Entangling neutrons via successive scattering from a substrate
  This letter details a simple scheme to entangle two neutrons by successive scattering from a macroscopic sample. In zero magnetic field the entanglement falls as the sample size increases. However, by applying a field and tuning the momentum of the neutrons, one can achieve a substantial degree of entanglement irrespective of the size of the sample. 
M. Avellino, S. Bose, A. J. Fisher