Theoretical Study Of Nonclassical Effect And Its Application In Optomechanical System

Cavity optomechanical sy stem,composed of microwave cavity and mesoscopic or macro-scopic mechanical oscillator,can be used to study micro-macro entanglement,ultra-sensitive measurement,quantum information storage,and hence is an important device.The dissertation focuses on cavity optomechanical system and investigates the mechanical squeezing,entangled cat state generation,quantum transistor and quantum illumination,which plays an important role in quantum information storage and ultra-sensitive detection.Firstly,the development history of quantum physics is introduced,and the recent progress of cavity optomechanical system is analyzed.Based on the background of cavity optomechani-cal sy stem,the research motivation of the dissertation,research content and the arrangement of each chapter are followed.Then the basic knowledge of quantum optics,open quantum system and cavity optomechanical system that related to the research content of this dissertation are given.Then,several research works are presented.With the assistance of non-Markovian environment,a scheme is proposed to enhance the mechanical squeezing(see Chapter 3).It is found that both the cavity mode and non-Markovian reservoir can induce the effective parametric amplification term of the oscillator,thus realizing the mechanical squeezing.By using Lyapunov control,a scheme is proposed to realize mechan-ical squeezing beyond 3 dB(see Chapter 4),where by designing the time-dependent modulation of the oscillator,it is derived that the momentum variance of the oscillator can be monotoni-cally decreased without divergence in the parameter region of weak coupling,thus realizing the mechanical squeezing over 3 dB.Furthermore,the method that induces the time-dependent frequency by auxiliary cavity mode is given.A scheme is proposed to realize strong mechan-ical squeezing in the unresolved-sideband regime(see Chapter 5).By introducing a nonlinear medium,it is found that the quantum backaction heating can be completely removed.Then the quantum backaction cooling limit is not affected by the cavity decay,so that even in the unresolved-sideband parameter region,the ground state cooling of the dressed mode can still be realized.Accordingly,the strong mechanical squeezing can be realized by the joint effect of the dressed mode cooling and parametric amplification.A scheme to realize the entangled cat state of two mechanical oscillators is proposed(see Chapter 6).By introducing the modulated coupling between the two optomechanical cavities,the entangled cat state with large average phonon number and high degree of entanglement can be realized.The results show that in the open system,although the dissipation of the system and the thermal excitation of the environment will destroy the scheme to produce the entangled cat state,under the optimized parameters,the scheme can still produce the entangled cat state with high fidelity.A scheme for constructing quantum transistor is proposed based on cavity optomechanical system(see Chapter 7).The behavior of the three ports are analyzed by considering the quantum signal and the classical signal input at the base port.In the case of quantum signal input from the base,it is proved that the signal of collector and base can be transmitted to emitter through trimer interaction,and the transmission is greater than the reflection.In the case of classical signal input from the base,based on different parameters,we can get the beam splitter type interaction and parametric down-conversion type interaction between the collector and emitter,respectively.By analyzing the relationship between the input and output,we prove that both of the two cases can realize the function of quantum transistor.In order to improve the microwave quantum illumination,an OPA crystal is introduced into the optomechanical cavity of the electro-optomechanical system(See Chapter 8).The results show that the OPA crystal can enhance the entanglement between the output light field and the microwave field,thus can enhance the microwave quantum illumination and reduce the error probability of detection.Even though the reflectivity of the target object is very low,the scheme still has high SNR and low detection-error probability.Compared with the conventional microwave radar,the scheme has obvious advantages.All of these researches should be valuable for the future potential application of cavity optomechanical system.