Quantum Teleportation In Different Channels

This dissertation discusses the quantum teleportation of canonical variables and a non-maximally-entangled quantum channel. The entanglement teleportation is realized via a channel of entangled thermal mixed states in 1D Heisenberg chains. The impacts of quantum noise of amplitude damping on every stage of teleportation is analyzed. In the theory of quantum communication, an unknown quantum state can be remotely teleportated by means of local unitary operations and classic channels (LOCC) if a quantum channel of entangled states is constructed by two parties of the teleportation. From the fundamental theory of the teleportation, an arbitrary two-partite state can be teleported via a quantum channel of common eigenstates of number sum operator and phase difference operator. It is found that the unitary operation of canonical teleportation is more general and can be used to simplify the process. In the experiments of quantum communication, maximally entangled pure states are difficult to prepare due to the effects of environment. Therefore, a quantum channel is always represented by mixed states. The thermal equilibrium state in solid state materials is one essential mixed entangled state. In this dissertation, a two-partite entangled state can be teleported through the channel of thermal mixed states in two independent 1D Heisenberg chains. The effects of temperature and external magnetic fields on the output entanglement and the fidelity of teleportation is analyzed. It is found that the entanglement will be decreased after the teleportation. If the entanglement provided in the channel is greater than a critical value, the entanglement teleportation will be realized. When the Heisenberg coupling is weak, the external magnetic field can improve the fidelity to some degree. To evaluate the capacity of transferring classic information by such quantum channels, the mutual information is also calculated. It is shown that the mutual information will decrease when the temperature and the magnetic field are increased. The entanglement quality of the input signal states cannot enhance the mutual information. Due to the measurements, the systems interact with the environment. The quantum noise will appear in the channels. This dissertation studies the influence of the quantum noise of the amplitude damping on the fidelity of the teleportation. The geometric figures are used to represent the loss of quantum information because of the quantum noise. It is shown that the teleportation is always superior to the classic communication even if the noise is strong in the channels.