Study On Quantum Entanglement And Mechanical Squeezing In Hybrid Atom-optomechanical System

Cavity optomechanics is a frontier of physics mainly focus on the study of the interaction between optical fields and micro-or macro-mechanical systems.Cavity optomechanics is not only of great significance in fundamental scientific research such as quantum correlation and quantum state generation,but also helps to solve practical problems faced by various fields today,such as achieving high-precision temperature measurement,highly sensitive sensors,and quantum computing.By studying the coupling of light and mechanical vibration in cavity optomechanical system,we can deeply understand quantum mechanical vibration,quantum measurement and quantum information.The hybrid atom-optomechanical system have broad application prospects,and can achieve photon coupling between atoms and cavity fields under current experimental conditions.This paper studies the entanglement and mechanical squeezing in the hybrid atom-optomechanical system from the following two aspects:Firstly,mechanical squeezing and steady-state entanglement in dispersive atomoptomechanical system were studied.Strong mechanical squeezing in traditional optomechanical systems generally requires the optical decay rate to be smaller than the mechanical oscillator frequency(the resolved-sideband condition),which is difficult to achieve in the laboratory.In order to generate strong mechanical squeezing and steadystate entanglement in optomechanical systems under high unresolved-sideband conditions(where the optical decay rate is much larger than the mechanical oscillator frequency),we propose a scheme to modulate the optomechanical system via two twolevel atomic ensembles.The constraints of the resolved-sideband condition can be relaxed significantly.The research results show that by introducing two atomic ensembles into the optomechanical system,strong mechanical squeezing exceeding 3dB can be achieved even under high unresolved-sideband conditions,and steady-state entanglement between the optical field and mechanical oscillators can also be generated.Next,entanglement and mechanical squeezing in a hybrid system formed by two two-level atomic ensembles and an dissipative optomechanical system were investigated.The system is driven by two lasers with different intensity.It was found that the entanglement between the two atomic ensembles can be controlled through the system’s dissipative and dispersive couplings.If the dispersive coupling is taken into account,the maximal entanglement between the atomic ensembles may be greater than in the case of pure dissipation.Stationary entanglement exists in the present optomechanical system,and entanglement increases with the decay rate of the mechanical oscillator and the power of the driving laser.Strong mechanical squeezing greater than 3dB can also be generated in the present atom-optomechanics hybrid system.