Optical experiments beyond the quantum limit: Squeezing, entanglement and teleportation

We report results of experiments recently performed at the Australian National University. Two optical parametric amplifiers were set up to generate two independently quadrature squeezed continuous wave laser beams. We demonstrated the transformation of quadrature squeezed states into polarization squeezed states and into states with spatial quantum correlations. Utilizing two squeezed laser beams we were able to generate a polarization squeezed state which exhibited three simultaneously squeezed Stokes operator variances. We generated continuous variable polarization entanglement and observed the Einstein-Podolski-Rosen paradox. A pair of Stokes operators satisfied both the inseparability criterion and the conditional variance criterion. We observed values of 0.49 and 0.77, respectively, with entanglement requiring values below unity. The inseparability measure of our observed quadrature entanglement was 0.44. This value is sufficient for a demonstration of quantum teleportation which is our next experimental goal.