Research On Quantum Dialogue And Two-way Quantum Teleportation

Communication, from transmitting message through flame in ancient times tochatting with each other on phones or on the Internet in modern times, has beengreatly changing people’s daily life. Even people across the ocean can clearly see orhear each other through modern ways of communication. People have been givengreat hope by the revolution of technology. The demands of people on communicationhave been largely improved after basic requirements had been met. Nowadays, thesecurity and efficiency of communication have been the priority. The classicalcommunication could not meet people’s requirement gradually because thetechnology has been greatly developed by Technological Revolution. Therefore,quantum communication appears at the historic moment. When it comes to quantumcommunication, the concept of quantum teleportation, which is an important step inthe process of quantum theory applied in communication research, must be involved.It is worth mentioning that the quantum teleportation is a one-way transmitting, and itis not communication in its true sense. Therefore, we do a further study and proposethe schemes of two-way quantum teleportation and quantum dialogue along with thesecurity analysis, in order to provide new ideas to achieve quantum communication inreal life.This thesis has been divided into four chapters. In the first chapter, we brieflyintroduce the current research of quantum communication and the research results athome and abroad. In the second chapter, we analysis the controlled quantumteleportation based on cluster states. In the last two chapters, we propose two schemesof controlled two-way quantum teleportation and controlled quantum secure dialogue.Due to the join of a third party, security of quantum communication is greatlyenhanced, which makes the schemes more applicable.The main points and innovation of this paper are listed as follows:(1) A scheme of two-way quantum teleportation controlled by a third party isproposed. Two sides of communication (Alice and Bob) and the controller Charlieshare a six-qubit cluster state in advance to construct quantum channel. Takingadvantage of better correlation and high entanglement degree of the cluster state,two-way communication could be achieved more secure and efficient. Firstly, twosides of communication perform Bell-state measurements on parts of their qubit pairs, respectively. If Charlie agrees them to communication, he should measure his qubitsand announce the states. According to Charlie’s measured results, Alice and Bobperform some appropriately unitary transformations on their qubits respectively. Thenthey are able to reconstruct each other’s unknown state on their own qubits. In thisscheme, we achieve the goal of two-way communication by fulfilling quantumtwo-way teleportation based on one-way quantum teleportation. The security oftwo-way communication has been largely improved because of the control of a thirdparty. Through further analysis and comparison, we know that the security ofcommunication system could be improved by increasing controller’s qubits. Butfurther increasing will not help to improve the security of quantum channel when itcomes to a certain level.(2) A scheme of two-way quantum communication controlled by a third party isproposed. Firstly, both sides of communication need accomplish informationencoding through some unitary transformations. Then they should perform Bell-statemeasurements on their own qubits respectively, and announce the measured results. Ifthe controller agrees them to communicating with each other, he performs a singlequbit state measurement on his own qubit and announces the result. Then the two-waycommunication can be achieved and the goal of quantum secure dialogue can berealized successfully. The encoded information transmitted in this system is classic,which makes the scheme better than two-way quantum teleportation and closer to realcommunication. Because of the third party’s control, the security of quantum dialoguecan be guaranteed, which makes the scheme more reliable and applicable.