Remote Preparation Of Arbitrary Two-and Three-Qubit States In Noisy Environment

Quantum communication is one of the core contents of quantum information and provides a new method for the secure transmission of information.As an important quantum commu-nication method,quantum remote state preparation(RSP)has achieved fruitful results both in theory and experiment.Because quantum system cannot exist independently in the real envi-ronment,it inevitably suffers from the influence of noise.The quantum entanglement is damped and the transmission of information is subject to errors.Therefore,it is significant to study RSP schemes under noisy environment.In this thesis,we study the deterministic remote state preparation(DRSP)protocols of arbitrary two-and three-qubit states using the ? state and Brown state as the entangled channel respectively.And we analyze the effects of seven types of noise(the amplitude-damping noise,phase-damping noise,Pauli noises and collective dephasing noise).The main results are as follows:1?Using the four-particle ? state,we put forward two DRSP schemes of arbitrary two-and three-qubit states.Compared to the previous RSP protocols,the local unitary operations adopted in this thesis are only single-particle Pauli operations without using the complex multi-particle unitary operations.It is worth mentioning that the success probabilities of the schemes have been greatly improved and reach 100%.Moreover,it has no restrictions on the complex coefficients of the prepared state.It means that the schemes have the wide range of application.In addition,the effects of seven noises are analyzed on the schemes.For each noise,we not only calculate the output state and fidelity,but also the average fidelity and the state-independent average fidelity.The results show that the fidelities are related to the amplitude parameter,phase parameter and noise parameter.Except for the amplitude-damping and collective dephasing noise,the fidelities are independent of the measurement results in other noises.The degree of information distortion is the largest in the Pauli noises and is the smallest in the phase-damping noise.2?We research the influence of the above seven noises on the DRSP via the Brown state.Similar to the analysis of noise effects on the RSP via the ? state,similar results are obtained.In addition,by comparing the protocols via the ? state and Brown state,it can be seen that when the prepared state is the maximally entangled three-qubit state,the fidelities are identical in the same noise.When the prepared state is an arbitrary two-qubit state,the state-independent average fidelities are identical in the same noise.In other words,there is the same degree of information distortion caused by noise.It means that the effects of noise is independent with not only what kind of channel is used,but also how to distribute the particles used in the quantum channel.These conclusions may contribute to improve the efficiency and safety of quantum communication in noisy environment.