Quantum Emitters in Complex Environments

Abstract

This thesis develops and applies tensor network methods to study non-Markovian quantum dynamics in open quantum systems, with particular focus on quantum emitters in complex environments and systems coupled to non-stationary baths. We apply the process tensor time-evolving matrix product operator (PT-TEMPO) framework and use the uniform TEMPO (uniTEMPO) method, achieving significant computational improvements for calculating multi-time correlation functions. The transfer tensor method is applied to propagate dynamics beyond the initial memory window, enabling efficient simulation of long-time behaviour. We apply these methods to investigate single-photon emitters coupled to phonon environments, computing key figures of merit including indistinguishability, efficiency, and emission spectra. Our analysis reveals that bulk acoustic phonons dominate decoherence, whilst localised optical phonons can be effectively suppressed through coupling to an optical cavity. We study emitters in various material platforms, including self-assembled quantum dots, hexagonal boron nitride defect centres, and tungsten diselenide quantum dots, providing guidance for optimising quantum photonic devices. We extend the framework to study initially non-stationary environments by investigating systems coupled to uniformly squeezed thermal baths. This represents the first application of process tensor methods to non-thermal environments, revealing enhanced non-Markovian behaviour and novel dynamical features. Our work demonstrates tensor networks as powerful tools for understanding complex quantum dynamics in engineered environments, advancing both fundamental understanding and practical applications in quantum technologies.

Date of Award	1 Sept 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Richard Curry (Co Supervisor) & Thomas Elliott (Main Supervisor)