Generation Of Multicolor Multipartite Entanglement On Nonlinear Processes

The study of quantum information is based on the basic principles of quantum mechanics.In the process of research,quantum coherence is used to explore new ways of quantum information computation,quantum coding and quantum information transmission.Quantum coherence and its quantum effects are the key to quantum information.Because of the principle of quantum parallel computing,quantum computing is superior to classical computing.The basis of quantum cryptography is the collapse of wave packet in quantum measurement.However,the basic of quantum communication is the representation of coherent superposition-quantum entanglement.As an elemental component of quantum communication,the preparation and application of quantum entanglement have attracted much attention.Since the founders of quantum mechanics put forward the EPR paradox and the Schr?dinger cat state in the 20 th century,quantum entanglement has become a fundamental research topic in the theory and application of quantum mechanics.Quantum entanglement has become a frontier problem in quantum theory and quantum technology.With the progress of entanglement sources,in order to meet the needs of quantum network and quantum communication development,entanglement between more than two particles is the research direction.Especially,multicolor multipartite entanglement has become a hot research topic in the field of quantum optics because of their advantages in network storage and transmission of information.This thesis is devoted to the theoretical study of the preparation of continuous variable multipartite entangled states.The main contents include:1,The concept and classification of quantum entanglement are introduced.And the background of applications and generation schemes of continuous variable multipartite entangled light is described in particular.2,A frequency up-conversion scheme for tripartite entangled light is studied.In this scheme,tripartite entangled light field is injected to a FP cavity through an input-output coupling mirror.Three optical modes interact with a non-linear crystal respectively and type I second harmonic generation(SHG)happens in each crystal.It is found that the output SHG light field retains the tripartite entanglement characteristics of the input light field.That is,frequency up-conversion was accomplished.3,Based on the reports of EPR generated by coupled waveguides,the feasibility of using coupled waveguide optical parametric oscillator to generate four-party entangled optical fields with continuous variables is studied.Coupled waveguide optical parametric oscillator consists of two parallel waveguides with second-order nonlinearity placed in an optical cavity.There is a linear coupling between them.Type I SHG and degenerate parametric down-conversion in waveguides are analyzed.The results show that both coupled waveguide optical parametric oscillators can generate quadripartite entanglement with the total amplitude quadratures of four modes and relative phase quadratures.4,Based on the quantum effects in the cavity optomechanical system,we study a ring cavity with two mechanical oscillators.After injecting light field(coherent laser or squeezed light),by analyzing the correlation spectrum between light field and two mechanical oscillators,it is found that the device can entangle the light field with two mechanical oscillators.And the entanglement degree of continuous variables tripartite entangement among photons and mechanical oscillators can be improved by injecting squeezed light.The three schemes have their own advantages.We analyze the relationship between the entangled states and the physical parameters(analysis frequency,pump intensity,coupling strength,temperature,etc.).We hope that the research will provide reference for the relevant experimental research.