The Quantum Coherence Control Based On Cavity Optomechanical System

Many efforts have been made to explore quantum effects in macroscopic systems.Cavity optomechanical systems provide a platform,where the quantum states of mechanics can be controlled,quantum superposition and quantum decoherence of macroscopic systems can be observed.It can help us to reveal the physical nature of the transition from quantum physics to classical physics.Recently,with the advances of mechanical ground-state cooling,a number of exciting progresses have been made in cavity optomechanics,such as optomechanically-induced transprency,squeezing of mechanical motion,entanglement between light and mechanics,and high precision measurement of small displacement and force.The interaction between photons and phonons in cavity optomechanics is intrinsically nonlinear.However,the present experimental studies are based on the so-called linearized model and neglect the intrinsic nonlinearity due to the limit of the strong coupling condition of single photon.Therefore,in the case of weak coupling condition,how to realize the deterministic manipulation of quantum states of light field and mechanical oscillator by using the nonlinear coupling between photons and phonons has become a challenging and very meaningful topic.Moreover,one of the outstanding characteristics of the cavity optomechanical system is that the freedom degrees of optics and mechanics can easily be coupled to constitute a optomechanical hybrid system with other physical systems such as cold atoms,BEC,LC circuit,and so on.To explore synthetically utilizing the advantage of different physical system in cavity optomechanical hybird system has important theoretical significance and practical significance for quantum communication and quantum computation.In this thesis,we mainly study how to realize single-photon nonlinearities in the single-photon weak coupling regime,control mechanical motion on the quantum level,and correlate optical and microwave photons in a hybrid electro-optomechanical system on the basis of the nonlinear dynamic evolutions of optomechanical systems.The main work includes:1.Optical nonlinearities at the single-photon level is realized in a quadratically coupled optomechanical system,where the cavity is coupled to the square of the mechanical displacement.The effective nonlinear interaction between photons and phonons is enhanced by a strong driving field,which allows one to implement the single-photon nonlinearities even if the single-photon coupling strength go is much smaller than the cavity decay rate ?.The second-order correlation function of optical fields are calculated by theoretical analysis and numerical simulation,and the photon statistical properties are discussed.The results show that the single-photon nonlinearities are robust against the mechanical thermal noise in the strong coupling and sideband-resolved regime,and photon blockade and photon-induced tunneling can be realized with experimentally accessible parameters.2.The Kerr type nonlinear interaction is obtained in a quadratically coupled optomechanical system.Although the phonon blocking effect has been studied in the nano mechanical oscillator,it is realized by coupling the mechanical oscillator with a two level system.So far,it has not been reported to realize the phonon blocking effect by using the coupling of optics and mechanics in the cavity optomechanical system.Based on the quadratically coupled optomechanical system,the strong Kerr type nonlinear interaction between phonons is gained by a near resonant driving field.At the sometime,the second-order correlation functions of phonons are calculated by theoretical analysis and numerical simulation,the phonon statistical properties are discussed,and the phonon blocking effect is acquired.In addition,if the cavity field and the mechanical oscillator are initially in coherent states,the cavity field and the mechanical oscillator will be entangled under the nonlinear interaction between photons and phonons.When the system evolves to a certain moment,the entanglement of the cavity field and the mechanical oscillator will be relieved,and the mechanical oscillator will be prepared in the Schrodinger cat state.3.The nonclassical correlation between the optical and microwave photons is found in a hybrid electro-optomechanical system,where the indirect interaction of the optical and microwave photons is obtained by the mechanical oscillator as the medium coupling optical and microwave fields,respectively.Under the condition that the mechanical oscillator is cooled to the ground state,analytical and numerical simulation results show that the cross-correlation function between Stokes and anti-Stokes photons strongly violates the Cauchy-Schwarz inequality,which confirms the nonclassical correlation between the optical and microwave photons.The nonclassical photon pairs with vast different wavelength may have great potential applications in quantum information science.