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Edward H. Farhi and Peter W. Shor. Zhu, Elton Yechao. Massachusetts Institute of Technology. Department of Physics. Massachusetts Institute of Technology. Department of Physics 2019-12-13T18:53:51Z 2019-12-13T18:53:51Z 2019 2019 https://hdl.handle.net/1721.1/123242 1130059390 Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2019 Cataloged from PDF version of thesis. Includes bibliographical references (pages 165-172). Quantum information theory is an important element of quantum computing and quantum communication systems. Whenever a quantum computer needs to send an output state to another party, or two parties need to establish quantum entanglement or secure keys via quantum communication, a quantum channel is inevitably involved. Hence it is absolutely important to understand the properties of quantum channels for the purpose of communication. Here, quantum entanglement plays a huge role. Pre-shared entanglement could enhance the capacity, whereas entanglement across inputs could render the capacity formulae impossible to compute. The first part of this thesis seeks to address this issue, by studying the additivity properties in the communication of classical and quantum information, with or without entanglement assistance. I also study the reverse problem that, given a channel capacity, what can be said about the quantum channel itself. Quantum information theory also serves as an important tool in understanding other systems, for example, black holes. In this thesis, I model a closed random system by a unitary channel, and study how typical unitary channels process information. This provides huge insight into the strength of generalized entanglement measures, and the hierarchies in the complexity of information scrambling. by Elton Yechao Zhu. Ph.D. Ph.D. Massachusetts Institute of Technology, Department of Physics 172 pages eng Massachusetts Institute of Technology MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission. http://dspace.mit.edu/handle/1721.1/7582 Physics. Information-theoretic aspects of quantum channels Thesis application/pdf 2019-12-13T18:53:50Z Publication Doctoral Phys unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="5fb41940-4a45-4c15-8f50-b63fbc8b448b"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Information-theoretic aspects of quantum channels</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2019</PublicationDate> <Authors> <Author> <DisplayName>Zhu, Elton Yechao.</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Physics.</Keyword> <Abstract>Quantum information theory is an important element of quantum computing and quantum communication systems. Whenever a quantum computer needs to send an output state to another party, or two parties need to establish quantum entanglement or secure keys via quantum communication, a quantum channel is inevitably involved. Hence it is absolutely important to understand the properties of quantum channels for the purpose of communication. Here, quantum entanglement plays a huge role. Pre-shared entanglement could enhance the capacity, whereas entanglement across inputs could render the capacity formulae impossible to compute. The first part of this thesis seeks to address this issue, by studying the additivity properties in the communication of classical and quantum information, with or without entanglement assistance. I also study the reverse problem that, given a channel capacity, what can be said about the quantum channel itself. Quantum information theory also serves as an important tool in understanding other systems, for example, black holes. In this thesis, I model a closed random system by a unitary channel, and study how typical unitary channels process information. This provides huge insight into the strength of generalized entanglement measures, and the hierarchies in the complexity of information scrambling.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>