Information-theoretic aspects of quantum channels

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.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Physics

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2019

Author dc:creator

• Zhu, Elton Yechao.

Advisor dc:contributor.advisor

• Edward H. Farhi and Peter W. Shor.

• Physics.

Statement dc:rights

• 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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/123242

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/123242