The Effects Of Intrinsic Decoherence On The Entanglement And Teleportation In A Three-qubit Heisenberg Spin Chain

The quantum entanglement existing in the multiple subsystems of a quantum system is the most fascinating feature of quantum mechanics that the measurement on a subsystem can't be independent of the measurement parameters in other subsystems. In recent years, though, with the fantastic development of quantum information, quantum entanglement has gradually become hot topic, yet it is not a concept newly born. Occurrence of"Entanglement"begins with the time when quantum mechanics first came into being. The Heisenberg spin chains, as the natural candidates for the realization of the entanglement, showed some substantial advantages compared with the other physical systems in quantum information processing. Quantum teleportation teleportation is a fascinating phenomenon based on the nonlocal properties of quantum entanglements and plays an important role in quantum information. During teleportation, the unknown teleported state in the sender's qubit is destroyed and then reconstructed in the target qubit, the whole process relies on local unitary transformations and some assistance of classical communication. Unfortunately, decoherence destroys the quantumness of the system and hense will decrease useful entanglement between the parts of the system. There are several approches to consider the decoherence and solve the quantum to classic transition problem. One of these approaches is based on modifying the Schrodinger equation in a such way that the quantum coherence is automatically destroyed as the system evolves. This mechanism is called"intrinsic decoherence"and has been studied widely by scientists.This dissertation is composed of four chpaters and organized as follows. The first two chapters introduce the general development of quantum information theory and some fundamental knowledge relevant to quantum entanglement. Chapter 3 mainly investigates the influence of the intrinsic decoherence on entanglement and three-body teleportation in a three-qubit Heisenberg XX spin chain model in the presence of inhomogeneous magnetic field and Dzyaloshinskii-Moriya (DM) interaction. The inhomgeneous magnetic field is found to have a more significant role than the others in icreasing the pair wise entanglement and the teleportation. Chapter 4 investigates the effects of intrinsic decoherence on the pairwise entaglement and the three-body teleportation in the three-qubit Heisenberg spin chain XXX and XXZ, respectively. The results show that the external magnetic field plyas constructive role in the increase of entanglement and the teleportation.