  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.
