Implementing Quantum Walks Using Orbital Angular Momentum of Classical   Light
  We present an implementation scheme for a quantum walk in the orbital angular momentum space of a laser beam. The scheme makes use of a ring interferometer, containing a quarter-wave plate and a q plate. This setup enables one to perform an arbitrary number of quantum walk steps. In addition, the classical nature of the implementation scheme makes it possible to observe the quantum walk evolution in real time. We use nonquantum entanglement of the laser beam's polarization with its orbital angular momentum to implement the quantum walk. 
Sandeep K Goyal, Filippus S Roux, Andrew Forbes and Thomas Konrad
quant-ph