Transmission Of Information And Remote Operation Of Quantum State

The transmission of information has been a main subject in the field of quantum. The most remarkable schemes about transmission of information include quantum teleportation and remote state prepraration(RSP). Based on the two schemes, these processes of transmission of quantum information are discussed. Reestablishment of quantum state in teleportation and RSP under noisy channels are investigated by using entangled state as resources. Furthermore, by characteristic of state-operator, remote operations are realized in the process of information. The main results of this thesis are as follows:1. In the scheme of teleportation, the state to be teleportated(the initial state) can be transmitted to a remote observer. But teleportation obeys quantum no-cloning theorem, the sender does not hold the initial state. About teleportation of a qubit, we propose a scheme in which the sender can reestablish the initial state at his place. This scheme includes tow stages: In the first stage, teleportation of a qubit is realized by multiparticle nonmaximally entangled state; In the second stage of this scheme, a state preparer is introduced. With help of preparer, the sender can again obtain the initial state. Due to using multiparticle nonmaximally entangled as resources, sender can only get copies of the initial state with some probability. This scheme is fit for reestablishment of entangled state in teleportation.2. the effect of noise on RSP is discussed. The trace distance is used to describe how close the initial state is to the output state. In two different kind of cases, we analyze the influence of noise on RSP. In the first case, we consider quantum channels are a mixture of Bell states. Studies show the trace distance depends on mixture ratio and characteristic of initial state. In the second case, a maximally entangled state of the spin-1/2 particles is used as quantum channels. The spin-environment interaction is taken into account stochastic fluctuating mode. The density matrix of system is described by a suit of polarization vectors. By calculation, we obtain the expression of the trance distance, and analyze the effect of decoherence on the RSP.