Bright tripartite entanglement in triply concurrent parametric   oscillation
  We show that a novel optical parametric oscillator, based on concurrent $\chi^{(2)}$ nonlinearities, can produce, above threshold, bright output beams of macroscopic intensities which exhibit strong tripartite continuous-variable entanglement. We also show that there are {\em two} ways that the system can exhibit a new three-mode form of the Einstein-Podolsky-Rosen paradox, and calculate the extra-cavity fluctuation spectra that may be measured to verify our predictions. 
A. S. Bradley, M. K. Olsen, O. Pfister, R. C. Pooser