Entanglement between two macroscopic fields by coherent atom-mediated   exchange of photons
  Using two different criteria for continuous variable systems we demonstrated that pump and probe beams became quantum correlated in a situation of Electromagnetically Induced Transparency in a sample of Rb atoms. Our result combines two important features for practical implementations in the field of quantum information processing. Namely, we proved the existence of entanglement between two macroscopic light beams, and this entanglement is intrinsically associated to a strong coherence in an atomic medium. 
C. L. Garrido Alzar (1), M. Franca Santos (2), and P. Nussenzveig (1)   ((1) Instituto de Fisica, Universidade de Sao Paulo,...