Figure 1: Sketch of the system.
From: Enhanced nonlinear interactions in quantum optomechanics via mechanical amplification
Tunnelling between two optical cavities (blue circles) is mediated by a mechanical mode (red ellipse) on which a large-amplitude, strongly detuned parametric drive is applied to amplify its 
quadrature. This scheme results in an exponential enhancement of the single-photon coupling constant g, thereby amplifying the resulting effective photon–photon interaction.
