Study On Mechanical Squeezing And Quantum Correlation Based On Magnon-optomechanical Hybrid Systems

For a long time,quantum entanglement,quantum steering,and quantum squeezing have been important research objects in the field of quantum information,which have been used in the processing and communication of quantum information and ultrahigh precision measurement.With the gradual development of nano processing technology,optical radiation pressure-force,electrostatic force,and magnetostrictive effects have been widely utilized to couple phonons and optical photons,microwave photons,or magnons.These interaction mechanisms have contributed to the rapid development of magnon-optomechanical hybrid systems.In addition,the coupling between different particles makes it possible covert to the information encoded on different carriers,and therefore will contribute to the development of frontier technologies such as quantum networks,quantum computing,and quantum information processing.The realization of mechanical squeezing,quantum entanglement,and quantum steering in magnonoptomechanical hybrid system has attracted the interests of researchers in recent years.In this thesis,we mainly study how to utilize the auxiliary cavity mode to generate strong mechanical squeezing,use a two-mode squeezed microwave field to generate long-distance entanglement and asymmetric steering,and use of Coulomb coupling interaction and auxiliary cavity mode joint effects to generate and enhance quantum entanglement and steering.The main work includes:1.We propose a scheme for generating mechanical squeezing in a hybrid cavity magnomechanical system.It is found that the strong mechanical squeezing can be generated by optimizing the ratio of blue-detuned to red-detuned laser amplitude.However,the mechanical squeezing can not be generated when the blue-detuned laser is not applied.Furthermore,it is found that the two auxiliary cavities suppress the effect of the counter-rotating terms,leading to that the mechanical squeezing can break the 3 dB limit even when the dissipation rate of the magnon mode is much larger than the mechanical frequency.By contrast,if only one auxiliary cavity or no auxiliary cavity is coupled to magnon mode,the mechanical squeezing beyond 3 dB can not be achieved in a high dissipation of the magnon mode.This scheme provides an alternative way toward the practical implementation of mechanical squeezing in a hybrid cavity magnomechanical system.2.A scheme is proposed to generate long-distance entanglement and asymmetric steering between mechanical oscillator and magnon mode across the frequency difference of about 10 GHz in an optomagnonics-mechanical system composed of a magnon,a mechanical oscillator,and two cavities.The calculated results reveal that the longdistance magnon-phonon entanglement can be achieved due to the fact that the quantum correlation of the two-mode squeezed vacuum microwave field is successively transferred to the magnon mode and the phonon mode.Moreover,the entanglement is strong enough such that the quantum steering between magnon mode and phonon mode can be achieved in an asymmetric manner.Furthermore,the direction of quantum steering can be flexibly adjusted via changing the magnon damping rate,coupling strength,squeezing parameter,and bath temperature.The proposed scheme provides the possibility for the generation of macroscopic quantum entanglement and steering and has potential applications in quantum information processing.3.We theoretically explore the steady-state entanglement and steering between two charged nanomechanical oscillators in a hybrid four-mode cavity optomechanical system.We have shown that the Coulomb interaction between the mechanical resonators is the essential reason for the existence of entanglement between the two mechanical resonators that are separated in space.Our results show that by increasing the tunneling interaction strength,not only can entanglement be enhanced,but also two-way quantum steering can be generated.In addition,the enhanced entanglement becomes more robust against thermal noise.