Entanglement of the orbital angular momentum states of the photons   generated in a hot atomic ensemble
  Quantum protocols will be more efficient with high-dimensional entangled states. Photons carrying orbital angular momenta can be used to create a high-dimensional entangled state. In this paper we experimentally demonstrate the entanglement of the orbital angular momentum between the Stokes and anti-Stokes photons generated in a hot atomic ensemble using spontaneous four-wave-mixing. This experiment also suggests the existence of the entanglement concerned with spatial degrees of freedom between the hot atomic ensemble and the Stokes photon. 
Qun-Feng Chen, Bao-Sen Shi, Yong-Sheng Zhang, and Guang-Can Guo