Improving Atom-Mirror Entanglement and Mechanical Squeezing in a Modulated Optomechanical System

In this paper, the macroscopic quantum entanglement and squeezing in an unresolved-sideband atom-optomechanical system with a modulated optical parametric amplifier (OPA) inside the cavity are studied. Increasing the parametric gain of the OPA, the quantum-classical correspondence between the atom-mirror entanglement and classical nonlinear dynamics can be found. The critical point where the system experiences the transition from periodic oscillation to period-doubling motion can be characterized by the singularity of the atom-mirror entanglement. Furthermore, the dependence of the atom-mirror entanglement and mechanical squeezing on the detuning and the parametric gain of the OPA as well as the environment temperature are investigated in detail. It is found that the atom-mirror entanglement can be enhanced and the mechanical squeezing can be generated by modulating the OPA.