Quantum-criticality-induced strong Kerr nonlinearities in optomechanical   systems
  We investigate a hybrid electro-optomechanical system that allows us to obtain controllable strong Kerr nonlinearities in the weak-coupling regime. We show that when the controllable electromechanical subsystem is close to its quantum critical point, strong photon-photon interactions can be generated by adjusting the intensity (or frequency) of the microwave driving field. Nonlinear optical phenomena, such as the appearance of the photon blockade and the generation of nonclassical states (e.g., Schr\"{o}dinger cat states), are predicted in the weak-coupling regime, which is feasible for most current optomechanical experiments. 
Xin-You L\"u, Wei-Min Zhang, Sahel Ashhab, Ying Wu, and Franco Nori
quant-ph cond-mat.mes-hall