Research On Nonlinear Optical Properties Of Quantum Coherent Media Based On Quantum Manipulation

In recent years,based on the research on the quantum optical response characteristics of traditional cavity optomechanical system,many scholars have gradually turned to study the hybrid cavity optomechanical systems with various nonlinear media.Various hybrid cavity optomechanical systems have been proposed to promote effective optical-mechanical coupling in the system,for example,the introduction of degenerate optical parametric amplifiers(OPA)and high-order excited atoms in the Fabry-Perot cavity(FP)to achieve system tunable fast and slow light,a levitated dielectric nanosphere in the FP cavity to control the optical response characteristics of the system,embedding optical films in FP cavity to study quantum nonlinear effects in hybrid cavity optomechanical systems,etc.With the help of optomechanical interactions,we can explore many quantum mechanical effects of macro-mechanical oscillators in the system,such as optomechanical entanglement,ground state cooling,state preparation of the oscillator,and so on.The interesting quantum coherence and optical response characteristics produced in these hybrid cavity optomechanical systems make people gradually realize the importance of the research of them.With the development of quantum coherent control technology,the research of atom localization has also developed rapidly through laser operation.The contents of this paper are as follows:(1)We investigate the steady-state entanglement in an optomechanical system with a levitated dielectric nanosphere and a higher order excited atomic ensemble.The single nanosphere is trapped by an external harmonic dipole trap and coupled to the single-mode cavity field by the effective optomechanical coupling,which depends on the steady-state position of the nanosphere.We show that the steady-state optomechanical entanglement can be generated via the effective optomechanical interaction between the mechanical motion and the cavity mode.Further,these exist an optimal effective cavity detuning that maximizes the optomechanical entanglement.We also analyze in detail the influences of the excitation number of atoms,the radius of the nanosphere and the thermal noise strength on the steady-state optomechanical entanglement.It is found that the steady-state entanglement can be enhanced by increasing the excitation number of atoms and the radius of the nanosphere.(2)We study the influence of cross-Kerr(CK)coupling and optical parametric amplifier(OPA)on the effective frequency,damping,normal mode splitting,ground state cooling,and steady state entanglement of an optomechanical system formed by one fixed mirror and one movable mirror.The CK coupling could increase the damping of the movable mirror.The normal mode splitting of the output field is observed due to the CK coupling.The combination of the CK coupling and OPA decreases the minimum attainable phonon number and the effective temperature of the movable mirror.The amount of stationary entanglement between the mechanical and cavity modes can be enhanced by the weak CK coupling.In particular,we find the stationary entanglement becomes more robust against thermal fluctuations of the movable mirror in the presence of the weak CK coupling.(3)For an atomic system with cascade four-level type,a useful scheme about threedimensional(3D)atom localization is proposed.In our scheme the atomic system is coherently controlled by using a radio-frequency field to couple with two-folded levels under the condition of the existence of probe absorption.Our results show that detecting precision of 3D atom localization may be obviously improved by properly adjusting the frequency detuning and strength of the radio-frequency driving field.So our scheme could be helpful to realize 3D atom localization with high-efficiency and high-precision.In the field of laser cooling or the atom nano-lithography,our studies provide potential applications.