Quantum Correlation Dynamics Evolution And Its Optimal Regulation

The emergence of optical quantum theory initiates a deeply effect in the development of physics. The important concepts of describing microscopic particles non-locality-quantum correlations, which is called quantum correlation, lies at the heart of quantum mechanics and plays an extremely important roles in quantum physics. As a fundamental resource in quantum communication and quantum computation, quantum correlations have been widely investigated and have been applied in quantum teleportation, quantum computers, quantum cryptography and other fields. Since quantum systems can not avoid coupling with the environment, which leads to generate quantum decoherence. This made quantum systems emerge the phenomenon of the correlation intensity decay, entanglement sudden death and quantum correlation transfer in the process of quantum dynamics. This limits them to apply in dealing with quantum information and quantum computation. Exploring anti-fading environment of quantum correlation dynamical evolution process and looking for the approach of increasing the quantum correlation evolution intensity under different environmental conditions, are the very important and valuable research works to the development of quantum information theories and experiments. Using nonlinear media and weak measurement operation to optimize and control dynamics evolution in this article. The main work of our investigation are as follows:1. Research work of the characteristics of entanglement dynamical evolution of two two-level atoms in a closed system. We analyzed the dynamical evolution process under vacuum cavity field, particle number field, the nonlinear medium cavity field environment. Firstly, using the method of negative eigenvalue of partially transposed matrix, we investigated the evolution of initial entangled two-atom in a field of number state and Kerr-media environment. It is found that entanglement sudden death phenomenon can be eliminated and can make the value of entanglement degree of quantum state oscillates around a high-value under Kerr-media environment. Secondly, we researched the interaction between entanglement atoms and the optical cavity with an additional Kerr medium. Using the way of detecting entanglement, which is concurrence, we found that non-linearity and detuning can also eliminate the happening time of entanglement sudden death. Thirdly, we studied that initially entangled atoms interact with Jaynes-Cummings(J-C) model and Nonlinear Jaynes-Cummings(N-J-C) model respectively. The meaningful result is that entanglement sudden death vanishes in N-J-C model by using the effect of non-linearity and detuning in a certain condition. And to some extend, it can almost back to the original values of entanglement degree in the evolution process.2. Using the techniques of weak measurement, we studied the dynamics evolution and transfer of quantum correlation of two entangled quantum qubits in open system. Operating by weak measurement to the initial non-maximally entangled particles with entanglement sudden death happening, will not only improve the quantum correlations, but also can reduce or even eliminate the happening time of entanglement sudden death. When there is no entanglement sudden death happening in the evolution of non-maximally entangled initial state, it can reduce the intensity of qubits’ quantum correlation by weak measurement operation. The operation of weak measurement can not enhance entanglement between particles but can optimize quantum discord when particles are initially in maximally entangled state. Weak measurement has little effect in the quantum correlation transfer procession and can postpone the decay of entanglement, and even can make entanglement transfer happen earlier. In addition, the coupling strength between the cavity field and qubit and system dissipation rate can also affects its dynamical evolution, showing Markovian and non-Markovian process.3. We investigated the optimization and control of quantum correlation states in the process of dynamics evolution in open system environment based on weak measurements. By means of concurrence and quantum discord, it is found that weak measurement operation can decrease the occurrence time of entanglement sudden death in the process of time evolution. In Markovian environment, the quantum entanglement of quantum states decay rapidly and weak measurement can only optimize the time of quantum entanglement sudden death. In the case of maximum entanglement state, the operation of weak measurement cannot optimize the intensity of quantum correlation during the evolution process.