Study Of Quantum Teleportation With Thermal Entangled Quantum Channel And Cavity QED

This thesis discusses the thermal entanglement and average fidelity in the two-qubit Ising model with a uniform and nonuniform magnetic field, respectively. We also discuss a feasible scheme to teleport two unknown atoms using non-maximally entangled states without Bell-state measurement by Cavity QED.The original quantum teleportation means that the sender Alice transits an unknown qubit state to the distant receiver Bob. Note that what the special procedure transit is only the information of Alice's qubit state, while the original qubit remains in Alice's site, one cannot make exact copy and directly extract full information from the original state. Due to the uncertain principal of quantum mechanics, one cannot extract all information of the original quantum state exactly. Therefore, one divides all information into two parts: general information and quantum information. A classical channel informs general information and quantum information is informed by quantum channel. So, one can reconstruct all information of the original quantum state in the other place.In this paper, we present a scheme to teleport two unknown quantum states with the Ising chain, we discuss the fidelity as well. Because of the environment's affection, we can hardly teleport information with pure entangled states. Therefore, a quantum channel is always represented by mix states. So in this paper, we teleport a two-particle entangled state through the channel of thermal mixed states in 1D Ising chain. We study the effect of the external magnetic field, temperature and coupling coefficient on the concurrence and fidelity.Quantum information is based on the quantum state, of all the quantum state's preparation and operation to realize the management of the quantum information, cavity is the most important and promising hardware. The main idea is that we restrict the atom in high-Q cavity. We store the quantum information in the atom's energy state. As the atom interacts with the cavity, which leads to the interaction of the atoms and then make the state changed, and at last we realize the operation and preparation of quantum state. We can also use the cavity to realize the teleportation of unknown quantum state.Of the quantum information's management, the quantum system interacts with the environment, so it destroys the quantum system and loses some of the information. Most schemes are put forward to separate the quantum system with the surroundings as possible as we can, but it cannot avoid the degradation. In previous schemes of using the cavity to deal with the quantum information, cavity only acts as the memorizer, and the obstacle of the information's management is the degradation. So it requires the high quality of the cavity, but it is difficult to realize. Now, with the detuned interaction, which can overcome the shortcomings of the cavity decay. It is not sensitive to the thermal field and the cavity decay, so it does not require very high quality of the cavity, we can teleport unknown quantum qubit by QED successfully. In this paper, we use the detuned interaction between atoms and atoms in cavity, with GHZ non-maximally entangled state as the quantum channel to teleport two unknown quantum states.The paper is organized as follows: In the first chapter, we introduce the basic knowledge about the quantum teleportation and the quantum channel. The second and the third chapters are the main work we do. In the second chapter, we investigate the thermal entanglement and average fidelity in the two-qubit Ising model with a uniform and nonuniform magnetic field. In the third chapter, we propose a protocol for teleportation of two unknown atomic states using non-maximally entangled states on channel QED. And in the last chapter, we make some conclusion and foreground.