  Single photons emerging from q-plates (or Pancharatnam-Berry phase optical
element) exhibit entanglement in the degrees of freedom of spin and orbital
angular momentum. We put forward an experimental scheme for probing the
spin-orbit correlations of single photons. It is found that the
Clauser-Horne-Shimony-Holt (CHSH) parameter S for the single-photon spin-orbit
entangled state could be up to 2.828, evidently violating the Bell-like
inequality and thus invalidating the noncontextual hidden variable (NCHV)
theories.
