Studies On Optical Transmission And Quantum Blockade Effect In Hybrid Cavity Magnonical System

In recent years,as a rapidly developing sub-field of quantum engineering,the development of hybrid quantum systems has received great attention.Hybrid quantum systems provide an important way to integrate different quantum modules and make use of their complementary advantages.Among various hybrid quantum systems,the hybrid cavity magnonical system has become the focus for recent researchers.Theoretical and experimental studies have proved that the collectively excited magnon by yttrium iron garnet(YIG)in the hybrid cavity magnonical system can interact with various quantum modules,such as microwave photon,optical photon,phonon and superconducting qubit.The study of quantum effects of light and matter in the hybrid cavity magnonical system has promoted the development of quantum communication,quantum information processing and other quantum frontier technologies.Based on the existing research progresses of cavity magnonical system,three different hybrid cavity magnonical systems are proposed in this dissertation.By selecting appropriate system parameters,the optical transmission and the quantum blockade effect of magnon in the systems are mainly studied.The specific research contents are as follows:(1)In a hybrid cavity magnomechanical system consisting of a YIG sphere and a microwave cavity,we focus on study of optical transmission properties in the hybrid system by solving the transmission spectrum of the system using Heisenberg-Langevin equation of the quantum optics.In this hybrid system,the microwave cavity is driven by a strong pump field and a weak probe field,and the YIG sphere is driven by a weak microwave source while being uniformly magnetized by an external bias magnetic field.Due to the excellent performance of ferrimagnet material,YIG sphere excite magnon while causing geometric deformation,resulting in mechanical phonon mode in the system.It is found that with the interaction of magnon-photon coupling and magnon-phonon coupling,there are two transparency windows and three absorption dips in the system.By changing the magnetic field amplitude of magnon driving field and the relative phase of external driving fields,the absorption caused by magnonphoton coupling can be modulated into asymmetric amplification and absorption.In addition,changing the magnetic field amplitude of magnon driving field and the relative phase of external driving fields also has a significant impact on the group delay of the system,which can realize the mutual modulation between fast light and slow light effects.The results we obtained provide a theoretical scheme for controlling the transmission of microwave optical signal in the cavity magnonical system.(2)In a hybrid cavity ferromagnet-superconductor quantum system consisting of two mutually perpendicular microwave cavities,two two-level superconducting qubits and a YIG sphere,we focus on study of magnon blockade effect of the hybrid system by solving the equal-time second-order correlation function of the system using the quantum master equation and Schr(?)dinger equation of the quantum optics.In the hybrid system,two superconducting qubits are mounted in the different microwave cavities.The magnon excited in the YIG sphere is coherently coupled with two superconducting qubits through virtual-photon of microwave cavities.In two cases with and without magnon-qubits detuning,it is found that in the strong coupling regime,the conventional magnon blockade effect(CMB)and the unconventional magnon blockade effect(UMB)can coexist in the system,which can be adjusted simultaneously by changing the magnon-qubits coupling strength ratio and the qubits detuning strength ratio.In the weak coupling regime,only UMB exists in the system.Without magnon-qubits detuning condition,the UMB of the system shows a nonmonotonic dependence on the magnon-qubits coupling strength ratio.With magnon-qubits detuning condition,for the optimal positions of the UMB,antibunching and bunching effects of the magnon can be realized the mutual conversion.In addition,it is found that the influence of thermal magnon excitation on the blockade effect of magnon can be also adjusted by changing magnon-qubits coupling strength ratio and the qubits detuning strength ratio.The results we obtained provide a theoretical scheme for controlling the blockade effect of magnon in the cavity magnonical system,and can be used for the preparation of the single magnon source.(3)In a hybrid cavity ferromagnet-superconductor quantum system consisting of two mutually perpendicular microwave cavities,two YIG spheres and a three-level superconducting qubit,we focus on study of the unconventional magnon blockade effect in YIG2 sphere by solving the equal-time second-order correlation function of the system using the quantum master equation and Schr(?)dinger equation of the quantum optics.In the hybrid system,superconducting qubit is arranged at the center of two microwave cavities.The magnons excited in two YIG spheres are coupled with different energy levels of three-level superconducting qubit through virtual-photon of the microwave cavities.With the help of the three-level system,it is found that in the weak coupling region,the unconventional blockade effect of the magnon in YIG2 sphere can be well realized through degenerate three-wave mixing process.In addition,it is found that the blockade effect of the magnon in YIG2 sphere can be flexibly adjusted by manipulating the coupling strength of YIG1 sphere and the three-level superconducting qubit,or the driving strengths of the system.The results we obtained provide an alternative scheme for constructing the single magnon source in the cavity magnonical system.