Four-particle Entangled W State Teleportation, Dense Coding Scheme For Remote Preparation Of Two-particle State And The Promotion

Quantum information is based on the basic principle of quantum mechanics, realizing encoding,computation and information transmission with various characters. Quantum teleportation,remote state preparation,quantum dense coding are important research task of quantum information science.In this thesis we will discuss three aspects as follows:1. Quantum teleportationWe propose probabilistic teleportation of a four-particle entangled W state using two two-particle partially entangled states as the quantum channel. We show that teleportation can be successfully realized with certain probability if the sender (Alice) performs three unitary transformations using basic quantum logic gates (Control-Not gate and Toffoli gate) and performs two Bell-state measurements while the receiver (Bob) introduces auxiliary particles and performs appropriate unitary transformations. Because of the feature of the quantum channel, the total maximal probability of success equals 1.2. Remote state preparationWe propose preparing two-particle state of general formation remotely using two EPR pairs and two two-particle partially entangled states as the quantum channel respectively. In this theme, two-particle state of general formation can be prepared remotely if the sender (Alice) performs one measurement and tells the result to the receiver (Bob) via classical channel and Bob performs appropriate unitary transformation according to the result of Alice. Because of the feature of the quantum channel, the total maximal probability of success equals 50%. The capacity of classical information is calculated and our scheme economizes classical information comparing with quantum teleportation.3. Quantum dense codingWe present a scheme for probabilistic dense coding between three parties, using a three-particle maximally state and a non-maximally entangled state as quantum channel respectively, and transmission efficiency is calculated. This scheme is generalized to the condition of three-particle random energy level non-maximally entangled state.