Identifying the orbital angular momentum of light based on atomic   ensembles
  We propose a scheme to distinguish the orbital angular momentum state of the Laguerre-Gaussian (LG) beam based on the electromagnetically induced transparency modulated by a microwave field in atomic ensembles. We show that the transverse phase variation of a probe beam with the LG mode can be mapped into the spatial intensity distribution due to the change of atomic coherence caused by the microwave. The proposal may provide a useful tool for studying higher-dimensional quantum information based on atomic ensembles. 
Liang Han, Mingtao Cao, Ruifeng Liu, Hao Liu, Wenge Guo, Dong Wei,   Shaoyan Gao, Pei Zhang, and Hong Gao
physics.atom-ph physics.optics quant-ph