Entanglement Dynamics Of Two Two-level Systems In Noisy Environment

Quantum entanglement is a very peculiar of the characteristics in quantum mechanics, it is also an important physical resource in the field of quantum information science and has been widely used. This paper mainly studies the entanglement dynamics of a two double-level atom system influenced by a noisy environment. A measure by concurrence, we investigate the change of entanglement for distributing, and entanglement sudden death in the noisy environment. The detailed content and structure is as follows:The first chapter is mainly arranged to review the emergence and development for the notion of quantum entanglement.The second chapter describes the basic theory of quantum entanglement. First we introduce the definition and its nature of quantum entanglement, then the entanglement dynamics approach:"super-operator theory and master equation method", and the derivation of master equation in the Markov approximation are described. In the third chapter, we investigate the entanglement dynamics of a two double-level atom system interacting with a collective noisy environment. In Markov approximation, we derive the master equation of the system and provide the exact solutions for a very general initial state. It is shown that for initially entangled states, the entanglement (measured by concurrence) may die either by monotonic or oscillating way. For initially product states, the entanglement enhancement and death can occur alternatively for finite time.In the forth chapter, we investigate the change of entanglement in the process of distributing an arbitrarily entangled two-qubit pure state via three typical kinds of noisy quantum channels-amplitude damping, phase damping and depolarizing quantum channels, where two kinds of transmission ways-one and two-qubit transmission are involved. We also study the optimal input states for entanglement distribution and the ESD phenomena via the three typical kinds of noisy quantum channels.In the last chapter, we make brief summary and prospects of the work in this paper.