Research On The Capacity Of A Teleportation-based Wireless Quantum Communication Network

Quantum communication is an interdisciplinary project consisting of quantum mechanics,information theory,and communication theory.The quantum communication network which is based on quantum information science uses the quantum bit(qubit)as the carrier of information transmission and takes advantage of the superposition and entanglement characteristics of a quantum state,which endow the quantum communication process with security and high efficiency.Besides,quantum communication creates a novel way for information processing and communication which is different from the traditional model.In recent years,the quantum networking industry has made continuous breakthroughs both theoretically and practically,and the quantum communication network has gradually become an important part of the future communication network.The network capacity is an important indicator and plays an important role in the deployment of quantum communication networks,hence,the research on quantum network capacity is of great importance.The capacity of a quantum communication network indicates,given a specify transmission model and resource limitation,the capability that quantum information is transmitted in the network.In this paper,the capacity of a quantum communication network is studied in three aspects,i.e.,the transmission of quantum information,the modeling and the simulation of a quantum network,respectively.Our research provides a unique insight on the internal mechanism of a quantum network,and can be concluded as follows:1.The multi-hop information transmission in a wireless quantum network is studied and multi-hop teleportation protocols are proposed and verified via simulation.The source codes are all publicly available.Quantum teleportation plays an important role in quantum communication networks.Most teleportation research focuses on the transmission of quantum states in single-hop situations.However,in the realistic quantum communication network,quantum state often needs to be transmitted between two non-adjacent ones.As a result,the intermediate nodes are used as repeaters to construct the transmission link,and Bell states and W states are used as the shared entanglement resources between nodes.Then,two multi-hop teleportation protocols are proposed.One is the hop-by-hop protocol,and the other is the improved multi-hop protocol.In the hop-by-hop teleportation protocol,we need to recover the transmitted quantum state on each intermediate node.In the improved multi-hop teleportation protocol,those intermediate nodes do not need to recover the transmitted quantum state.Besides,only those classic channels between each intermediate and the target nodes pair are needed,which significantly increases the confidentiality of the communication process.In addition,the improved multi-hop teleportation protocol can be executed in parallel,which can effectively reduce the communication delay.2.The capacity of a continuously distributed quantum network is studied.First,inspired by the classic networking theory,a distributed quantum network is defined,and this definition is able to effectively reflect the properties of a large wireless quantum communication network.Secondly,the modeling and analysis of the multi-hop transmission process in the quantum network is also carried out.It consists of three major parts,the routing process which aims at establish a route between source and destination nodes,the entanglement distribution technique to establish elementary links between adjacent nodes and the entanglement swapping protocol to create the end-to-end link between source and destination nodes.In addition,the definition of the capacity of a distributed quantum network is discussed,and capacity upper and lower bounds for,respectively,arbitrarily and randomly distributed quantum networks are also derived.3.Inspired by the classical wireless cellular communication system,the quantum cellular network is defined,and its structure and main components are also discussed.Further more,the network capacity in the case of a single cell is defined,analyzed and verified by simulation,and the relationship between block probability and number of terminal nodes in a cell is discussed.The derived results regarding to the network capacity is able to evaluate the performance of a quantum cellular network in the future and has both theoretical and practical values.4.A simulation system for the capacity of a wireless quantum communication network is designed and implemented with all relevant codes being open source.The system adopts a highly modular design and has a high degree of scalability.By replacing and updating the corresponding modules,the simulation and analysis for quantum networks with different typologies and protocols can be easily realized.Besides,the simulation performance of the system is analyzed.In addition,the simulation system is also used to analyze the influence of different parameters and communication protocols on the network capacity,based on which some suggestions are made for the optimization of a quantum communication network.5.The possibility of utilizing a quantum computer to simulate the capacity of a wireless quantum communication network is discussed,and an algorithm,called SAHS,is proposed as a crucial part in the quantum compilation process to tackle the quantum circuit transformation problem.SAHS has polynomial complexity and is able to significantly improve the quality of output solutions compared with the state-of-the-art algorithms,which may help increase the reliability of running a quantum program in a real quantum computer.The SAHS algorithm also provides a technological foundation for conducting the simulation on the capacity of a wireless quantum communication network in a real quantum computer in the future.