Enhanced Stationary Entanglement Induced By Optical Parametric Amplifier In Optomechanical System

Abstract

In this thesis, we theoretically studied the enhanced stationary entanglement in duced by optical parametric amplifiers in optomechanical system. To this aim, we constructed the model and Hamiltonian of system. While, the system consists of one fixed mirror and one movable mirror and a degenerate parametric amplifier placed between them. Thus, the cavity mode is driven by a laser field and degenerate para metric amplifier is pumped by another laser at a frequency of ωL. Accordingly, the dynamics of the system can be obtained by using the nonlinear quantum Langevin equations and linearization approximation. Under the linearization approximation, the bipartite entanglement is quantified through logarithmic negativity. Accordingly, our results show that the introduction of optical parametric amplifier makes the en tanglement more robust. Interestingly, we show that the effects gain, mass and tem perature have great contribution for the enhancement of the stationary continuous variable entanglement. Furthermore, under the resolved sideband regime, moderate optimal nonlinear gain and cryogenic temperatures the entanglement enhances as compared with system without optical parametric amplifier. Thus, when an optical parametric amplifier is added inside a cavity, the optomechanical coupling and the bipartite entanglement is improved. Such entanglements results may have spectac ular contribution for constructing long-distance quantum communication network and technologies.