Quasideterministic realization of a universal quantum gate in a single   scattering process
  We show that a flying particle, such as an electron or a photon, scattering along a one-dimensional waveguide from a pair of static spin-1/2 centers, such as quantum dots, can implement a CZ gate (universal for quantum computation) between them. This occurs quasi-deterministically in a single scattering event, hence with no need for any post-selection or iteration, {and} without demanding the flying particle to bear any internal spin. We show that an easily matched hard-wall boundary condition along with the elastic nature of the process are key to such performances. 
F. Ciccarello, D. E. Browne, L. C. Kwek, H. Schomerus, M. Zarcone and   S. Bose
quant-ph cond-mat.mes-hall