Classical entanglement: Oxymoron or resource?
  In this work we review and further develop the controversial concept of "classical entanglement" in optical beams. We present a unified theory for different kinds of light beams exhibiting classical entanglement and we indicate several possible extensions of the concept. Our results shed new light upon the physics at the debated border between the classical and the quantum representations of the world. 
Andrea Aiello, Falk T\"oppel, Christoph Marquardt, Elisabeth   Giacobino, Gerd Leuchs
quant-ph