Min Of Quantum States And Experimental Researches On Whispering-gallery-mode Microcavity

In my first year as a graduate student, I have studied the theory of quantum optics and quantum information, and have done some deep researches about measurement-induced nonlocality (MIN). From the beginning of my second year in the graduate school, I turn to do experimental researches on whispering-gallery-mode (WGM) microcavities instead of the theoretical researches on quantum information, because my advisor began to do experimental researches on WGM microcavities at that time. Therefore, this thesis contains two parts, one is the theoretical research about MIN and the other is experimental researcher about WGM microcavity.The first part of the thesis is about MIN. Quantum nonlocality has been a hot topic in physics since its beginning, and the study of quantum nonlocality is still in developing. As a quantum correlation, MIN is more general than the quantum nonlocality related to entanglement or the violation of Bell’s inequalities, so it is of importance to study the properties of MIN. In this thesis, we study the MIN in the states of the W and Greenberger-Horne-Zeilinger (GHZ) superposition. We first introduce the definitions of the MIN and the monogamy relation. Then we study the properties of the MIN in three or more qubits states of the W and GHZ superposition, and some interesting results have been obtained. Furthermore, we study the property of MIN in W and GHZ superposition when the particle number n goes to infinity. At last, we summarize the research content.The second part of the thesis is about WGM optical microcavity. WGM optical microcavity has ultrahigh quality factors and very small mode volumes, and due to these characteristics it has been applied in many fields, such as sensor, low threshold laser and quantum information processing. In the thesis, we first give a simple introduction to some background about WGM optical microcavity, including its developments and applications. Then we introduce the optical field theories about the spherical microcavity and the fiber taper, and the mode coupling theory in the system consisting of a spherical microcavity and a fiber taper. Next, we give some introduction to the experimental preparations of spherical microcavity and fiber taper from materials, methods, the construction of the experimental platform, the whole process of preparing and the influencing factors. At last, we describe some experiments done on our WGM microcavity platform, including the measurement of quality factors of our microspheres in air and aqueous solution, and the sensing experiment of the chromium nitrate.