Research On Quantum Key Agreement And Quantum Joint Remote Preparation

Quantum information is a new subject combined with quantum mechanics and information science, which has made a surprise progress both in theoretical and experimental field in the past three decades. Quantum communication is one of the most mature direction of quantum information. Quantum communication is a new means of communication. In quantum communication, there are two types of transmission information which is the quantum information and classical information. The most common way of classic information transmission is quantum key agreement. Quantum teleportation can be used for transmission of quantum information. This paper mainly discusses and solves some problems of quantum key agreement and joint remote preparation in quantum communication. To be specific, the work includes the following several aspects:(1) We reviewed C.Shukla et al.’s article in which they proposed the sufficient condition for unitary operator construction of quantum dialogue protocol and the solution for the unitary operation calculating. Through the further analysis and conclusion, we present a more perfect calculation method of unitary operator combinations. We use this method to find more operators suitable for arbitrary quantum states. In this way, we can achieve the biggest coding of arbitrary quantum state and improve the utilization rate of the quantum;(2) We analyze quantum key agreement protocol which C.Shukla et al.’s proposed and find they waste quantum resources, so we give the improved scheme. Besides, we expand two quantum key agreement protocol to multiparty quantum key agreement protocols based on n-qubit GHZ state. We use the appropriate unitary operation set according to the solution for the unitary operation we proposed to realize multiparty quantum key agreement protocols. Through the analyze internal collusion way Huang et al. proposed, we find we can use the way of "send at the same time" to avoid this kind of security vulnerabilities. In the way, we can ensure the safety of information.(3) Taking four EPR (Einstein-Podolsky-Rosen) pairs as quantum channel, a new protocol for deterministic joint remote preparation of four-particle Cluster-type states is presented. In the scheme, with some ingenious measure basis and four-step strategy for preparation, the receiver can get the target state. Compared with other protocols for deterministic remote preparation of arbitrary four-particle cluster-type states, our protocol is more efficient, and economic and feasible in the physical experiment. Besides, we extend three-To-one mode to N-To-one (N>2) mode for multiparty deterministic joint remote preparation of a four- particle Cluster-type state.