A simple scheme for quantum networks based on orbital angular momentum   states of photons
  We propose a new quantum network scheme using orbital angular momentum states of photons to route the network and spin angular momentum states to encode the information. A four-user experimental scheme based on this efficient quantum network is analyzed in detail, which is particularly appealing for the free space quantum key distribution. Users can freely exchange quantum keys with each other. 
Zhi-Kun Su, Fa-Qiang Wang, Rui-Bo Jin, Rui-Sheng Liang, Song-Hao Liu
quant-ph