Continuous-variable hyperentanglement in a parametric oscillator with orbital angular momentum.

We describe continuous-variable hyperentanglement in polarization and orbital angular momentum modes of an optical parametric oscillator. The quantum stochastic equations for the multimode parametric interaction are derived and solved allowing for calculation of the quadrature noise spectra that characterize continuous-variable entanglement. As a main result, we predict simultaneous entanglement between different combinations of amplitude and phase quadratures of the interacting modes. We also propose experimental setups to access the different kinds of entanglement.