Entanglement and the Einstein-Podolsky-Rosen paradox with coupled   intracavity optical downconverters
  We show that two evanescently coupled $\chi^{(2)}$ parametric downconverters inside a Fabry-Perot cavity provide a tunable source of quadrature squeezed light, Einstein-Podolsky-Rosen correlations and quantum entanglement. Analysing the operation in the below threshold regime, we show how these properties can be controlled by adjusting the coupling strengths and the cavity detunings. As this can be implemented with integrated optics, it provides a possible route to rugged and stable EPR sources. 
M.K. Olsen and P.D. Drummond