{"title":"Communication","authors":"J. Rau","doi":"10.1093/oso/9780192896308.003.0005","DOIUrl":null,"url":null,"abstract":"This chapter introduces the notions of classical and quantum information and discusses simple protocols for their exchange. It defines the entropy as a quantitative measure of information, and investigates its mathematical properties and operational meaning. It discusses the extent to which classical information can be carried by a quantum system and derives a pertinent upper bound, the Holevo bound. One important application of quantum communication is the secure distribution of cryptographic keys; a pertinent protocol, the BB84 protocol, is discussed in detail. Moreover, the chapter explains two protocols where previously shared entanglement plays a key role, superdense coding and teleportation. These are employed to effectively double the classical information carrying capacity of a qubit, or to transmit a quantum state with classical bits, respectively. It is shown that both protocols are optimal.","PeriodicalId":445393,"journal":{"name":"Quantum Theory","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Quantum Theory","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1093/oso/9780192896308.003.0005","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
This chapter introduces the notions of classical and quantum information and discusses simple protocols for their exchange. It defines the entropy as a quantitative measure of information, and investigates its mathematical properties and operational meaning. It discusses the extent to which classical information can be carried by a quantum system and derives a pertinent upper bound, the Holevo bound. One important application of quantum communication is the secure distribution of cryptographic keys; a pertinent protocol, the BB84 protocol, is discussed in detail. Moreover, the chapter explains two protocols where previously shared entanglement plays a key role, superdense coding and teleportation. These are employed to effectively double the classical information carrying capacity of a qubit, or to transmit a quantum state with classical bits, respectively. It is shown that both protocols are optimal.