A Research Of Preparation About Multi-Mode Continuous-Variable Entangled State

Since the concept of the quantum entanglement was proposed in the beginning of the last century, more and more scientists become familiar about this theory. But most of the research is on theoretical. In the 80’s of the last century, quantum communication has been put forward. It is based on the principle of quantum mechanics to ensure the safety in the process of communication. This makes the quantum entanglement applied more. As the basis for quantum communication, quantum entangled states are particularly important. This thesis is on the basis of previous studies. By means of cascaded cavity and vibrating membrance. we can get the entangled state as simple as possible. The main content about this thesis is as follows:1.We introduce the quantum entanglement and continuous variable quantum entanglement briefly. If we want to prepare the entangled state,we have to understand the quantum entanglement, including the classification and definition of quantum entanglement, and understand what conditions is better for the preparation of entangled states. We also should have a basically understanding about the quantum entanglement especially the continuous variable quantum entanglement. In addition, we also introduce the application status of entangled states in quantum information, especially the data obtained from the relevant scholars at home and abroad since twenty-first century.2. This part introduces the application of Electro Dynamics Quantum(QED). The development of QED is gradually mature, it can control the related particles in a sealed cavity, which can reduce the loss of the particle. Therefore, for the preparation of entangled state, the cavity of QED is a good carrier. Now a large number of preparation programs has been realized in this device.3. In this part, we introduce the preparation of entangled states specifically. Firstly, it’s about some previous preparation schemes and the development status. Then we draw the equipment in the preparation process.and have a specific description about the prepared process, including two cavity connected by optical fiber. And the two cavity basically is exactly same. We just place an atomic ensemble in the first cavity, and in the second cavity,we put on a vibrating membrance, then we drive the two cavity by the laser filed and mirrors. Finally, we can get the entangled state what we want through a series derivation about hamiltonian and density operator.4.In this part, we study the nonlocal entanglement and noise between spin qubits induced by Majorana bound states. We investigate the Majorana-modulated current noise cross correlations and dynamical spin entanglement between two electron spin qubits defined in quantum dots. As a good indicator of the entanglement of quantum spin, we can get the entanglement by observing the current noise cross correlations.