Dynamics and phases of matter in open quantum many-body systems
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Date
2024-06-24
Authors
Sang, Shengqi
Advisor
Hsieh, Timothy
Melko, Roger
Melko, Roger
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
The thesis is divided into two parts, both focusing on the topic of open quantum many-body systems.
The first part explores the properties of quantum circuits interspersed with measurements. Tuned by the frequency of measurements, the circuit exhibits two stable dynamical phases: a weakly-monitored phase and a strongly-monitored one. For the former case, we analyze its non-equilibrium properties and unveil that it exhibits physical length scales that grow super-linearly with time. For the latter case, we demonstrate that it can maintain non-trivial quantum order when symmetries are present.
The second part addresses phases of matter for mixed many-body states. We propose a real-space renormalization group approach for mixed states and apply it to derive phase diagrams for various examples. For decohered topological codes, we establish a precise relationship between the decodability and the topological phase transitions. Lastly, we introduce the notion of 'Markov length', a length scale that measures the locality of correlation, as a diagnostic for the stability of mixed state phases.
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Keywords
physics