Research On Ground State Cooling Of The Mechanical Resonator In Cavity Optomechanical Systems With Intracavity Squeezing

The development of cavity optomechanincs is accompanied by the progress of physics and informatics.As the important part of quantum mechanics,cavity optomechanics is the effective platform for studying the interaction between the light and mass.Cavity optomechanics has wide application prospects in both basic physics and quantum informatics,but those applications all have a crucial prerequisite that the mechanical resonators need to be cooled to its quantum ground state.With the rapid development of materials science and nanotechnology,high precision cavity optomehanical systems are constantly proposed.But there still exist some limitations.Such as the intrinsic dissipation,ambient thermal noise of the coupled heat reservoir and the heating caused by the quantum backaction force.In order to study the quantum properties of the macroscopic objects with large mass and low vibration frequency by means of optomechanics,the strict resolved sideband condition that could affect the application of cavity optomechanics should be satisfied.Based on the study of the ground state cooling of the mechanical resonator,this thesis proposed two cooling schemes to discuss how to utilize the intracavity squeezing to break through the limit of the resolved sideband and the influence of the thermal noise,then achieve the cooling beyond the standard quantum limit.A scheme based on the hybrid intracavity squeezing optomechanical system is proposed.The intracavity squeezing caused by placing the nonlinear medium in the cavity generates destructive interference in the dissipation channels,which coherence suppressed the quantum backaction heating.And at the same time,the cooling process of the system is manipulated by coupling with the optical cavity,which not only suppresses the heating,but also increases the cooling rate.The best squeezing parameter for cooling the mechanical resonator is studied,and the prefect suppression of the quantum backaction heating is realized.The cooling rate is greatly improved,and the cooling limit is reduced.We demonstrated that this scheme has the advantages that other schemes do not have.With the assistance of the intracavity squeezing and the auxiliary optical cavity,the high-quality requirement of the cavity for ground state cooling is greatly reduced and the thermal noise resistance of the system is improved.The cooling effect of the intracavity squeezing on the mechanical resonator in weakly quadratic coupled optomechanical system is also studied in this thesis.A nonlinear quadratic optomechanical coupling system that the membrane and nonlinear medium are placed in the cavity is proposed in this thesis.The cooling limit is studied and the best conditions of cooling are discussed with the advantage that the quantum heating can be controlled independently by the intracavity squeezing.By manipulating the system parameters,the cooling in the weakly quadratic optomechanical system can be achieved beyond the resolved sideband limit,and it also has better of thermal noise resistance.