Figure 3: Nonclassical photon intensity correlations.

Intensity correlation function , for a mechanical parametric drive yielding the optomechanical interaction (cf. equation (2)), and for a weak coherent probe tone applied to the cavities. In a, is plotted as a function of g for different values of the amplification factor e^2r; in b it is plotted as a function of e^2r for a fixed value of g. For each value of g and r, the probe frequency and the parametric-drive detuning Δ are optimized to minimize (Δ is plotted in insets). The amplitude of the weak probe is kept fixed. (a) The violation of the classical bound is enhanced in our scheme: the presence of the mechanical parametric drive leads to significant suppression of for experimentally accessible couplings . (b) Mechanical parametric driving brings the optical field deep into the nonclassical region even for g=0.05κ, leading to non-Gaussian optical fields (Supplementary Fig. 2). For these results, dissipative squeezing is used, with a damping rate γ_β=0.001κ.