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oai:figshare.com:article/32058150 2026-04-21T12:50:14Z portal_1132 item_type_8 month_year_04_2026

Geometry and Light in Quantum Optical Systems Oliver Fox (21041801) quantum quantum optics quantum mechanics nanophotonics This thesis looks at a range of quantum optical system with an emphasis on the geometrical structure. We first consider two coupled systems, a pair of 2-level systems and pair harmonic oscillators, with specific couplings to the environment through a Lindblad master equation. We look at observables such as optical spectrum to see the complex eigenvalues of the non-Hermitian systems. We compare the difference between how the linear oscillator and the non-linear truncated system behave at the steady state to find a dissipative phase transition. Next we consider a light-harvesting reaction-center model consisting of a ring of donor atoms coupled to a central acceptor. By introducing the Lindblad master equation, we model the effect of dissipation and dephasing, while also adding static disorder through site-specific randomness. We find high transfer efficiencies when coupled with a photon due to the geometry of the system transferring the excitation through a dark-state mechanism. Additionally, we find ways to mitigate the effect of negative the disorder of the photon-donor coupling has on the transfer efficiencies. We then consider the double excitation subspace of the same light-harvesting system, looking at a range of localised and delocalised conditions, as well as the system coupling to an incident photon pair. Singleand double-excitation transfer efficiencies were calculated, of up to 99% and 50%, respectively. Finally we consider a tight-binding lattice with an imbalanced geometry, consisting of two coupled layers: one with nearest-neighbour coupling and the other with nearest-neighbour and next nearest-neighbour coupling. We find localised states concentrated on the edge of a lattice in the finite sized model, with energies corresponding to the turning points in the bulk of the continuum bandstructure.<p></p> 2026-04-20T00:00:00Z Text Thesis 10779/exe.32058150.v1 https://figshare.com/articles/thesis/Geometry_and_Light_in_Quantum_Optical_Systems/32058150 All rights reserved