Quantum Entanglement Dynamics Via Two-field Driving In Cavity Optomechanical Systems

The realization of quantum entanglement manipulation promotes the rapid development of quantum information technology.Whether in the field of quantum communication or quantum computing,quantum entangled states are widely used,and their potential applications have been proved in various applications.The current research shows that the entanglement between the optical mode and the mechanical vibration mode can be realized by using the optomechanical interaction in the cavity optomechanical system,and the entanglement between different optical modes or mechanical modes can also be realized.This makes the research of cavity optomechanical system attracting more and more attention.Because variety of entangled states can be realized in such system,cavity optomechanical system is expected to be used in the field of practical quantum information and quantum communication.Based on the cavity optomechanical system,many people have proposed how to prepare the steady-state mechanical entanglement and optomechanical entanglement.The entanglement can be divided into two kinds: one is that the entanglement does not change with time when the system reaches its steady state;the other is that the entanglement still changes periodically with time when the system reaches its steady state.The preparation of periodic stable entanglement makes it possible for people to manipulate entangled states in time domain.At the same time,some methods have been proposed to prepare periodic stable entanglement.For example,using periodically modulated laser to drive the optomechanical cavity can achieve periodic optomechanical entanglement and mechanical entanglement;periodically modulating the frequency of mechanical oscillator can also achieve periodic optomechanical entanglement.These results provide useful guidance for us to further control the entanglement dynamics in the cavity optomechanical system.In this thesis,we first study the evolution of optomechanical entanglement with time by using a laser driven cavity with two modulation amplitudes.We find that by changing the relative value of the two modulation phases,the optomechanical entanglement can appear similar to the phenomenon of constructive interference or destructive interference in classical physics.Interestingly,when the two modulation frequencies are slightly different,the beat frequency phenomenon appears,and the beat frequency period satisfies the beat frequency law of classical physics.In this way,we can control the period of entanglement arbitrarily in time domain.Then,in the three mode optomechanical system containing two mechanical modes and one optical mode,we can get that the periodic mechanical entanglement can be achieved by three ways,which include periodic modulation driving laser,mechanical coupling strength and introducing controllable optical parametric amplifier(OPA).In addition,the mechanical entanglement with beat frequency can be achieved by the combination of any two of the three schemes.Our research shows that we can control the period of optomechanical entanglement and mechanical entanglement arbitrarily in the time domain.This study provides a meaningful reference for the application of cavity optomechanical system in the field of quantum communication and quantum information storage.