Cheng Shang, H. Z. Shen
ABSTRACT Observing few‐photon optomechanical effects remains a significant challenge in optomechanical systems. To investigate intrinsic radiation‐pressure‐induced nonlinear effects in the few‐photon regime, it is essential to strengthen the interaction between a few photons and a finite number of phonons. In this work, we enhance the radiation‐pressure nonlinearity by introducing a two‐laser coherent driving scheme together with an enhanced cross‐Kerr nonlinearity, resulting in a setup that can be effectively described within a circuit QED platform. By properly tuning the two driving laser fields and the cross‐Kerr interaction so that the effective optomechanical coupling becomes real, we theoretically establish a symmetric optomechanical model in which the photon and phonon modes exhibit analogous fluctuation dynamics. Within this framework, we analyze the optimal reciprocal transport of the input laser field and identify the critical boundary associated with the onset of different coupling regimes. We also compare the optical signal scattering behavior in both dissipative equilibrium and nonequilibrium symmetric optomechanical systems, with and without non‐rotating‐wave contributions. Our work provides a controllable route to enhance optomechanical coupling, extending into the ultrastrong‐coupling regime, and opens opportunities for exploring few‐photon optomechanical effects.