Photons can carry spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used to realize a qubit system and a high-dimension system respectively. This spin-orbital system is very suitable for implementing one-dimensional discrete-time quantum random walks. We propose a simple scheme of quantum walks on the spin-orbital angular momentum space of photons, where photons walk on the infinity OAM space controlled by their SAM. By employing the recent invention of an optical device, the so-called 'q-plate', our scheme is more simple and efficient than others because there is no Mach-Zehnder interferometer in the scheme.
@article{arxiv.1002.0638,
title = {Implementation of one-dimensional quantum walks on spin-orbital angular momentum space of photons},
author = {Pei Zhang and Bi-Heng Liu and Rui-Feng Liu and Hong-Rong Li and Fu-Li Li and Guang-Can Guo},
journal= {arXiv preprint arXiv:1002.0638},
year = {2010}
}