Improved quantum correlations in second harmonic generation with a squeezed pump

We investigate the effects of a squeezed pump on the quantum properties and conversion efficiency of the light produced in single-pass second harmonic generation. Using stochastic integration of the two-mode equations of motion in the positive-P representation, we find that larger violations of continuous-variable harmonic entanglement criteria are available for lesser effective interaction strengths than with a coherent pump. This enhancement of the quantum properties also applies to violations of the Reid-Drummond inequalities used to demonstrate a harmonic version of the Einstein-Podolsky-Rosen paradox. This could offer a real practical advantage over increasing the laser intensity, which will eventually damage the crystal, or using a larger crystal, in which case dispersion problems can be accentuated. We find that the conversion efficiency is largely unchanged except for very low pump intensities and high levels of squeezing.