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.
@article{arxiv.1107.4394,
title = {Quasideterministic realization of a universal quantum gate in a single scattering process},
author = {F. Ciccarello and D. E. Browne and L. C. Kwek and H. Schomerus and M. Zarcone and S. Bose},
journal= {arXiv preprint arXiv:1107.4394},
year = {2012}
}