Optical decoherence and coherent coupling of excitons in quantum dots embedded in photonic cavities

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This project in theoretical physics aims to study the coherent dynamics of optical excitations (excitons) in single and multiple semiconductor quantum dots (QDs) strongly coupled to photonic cavities. Your training and research will be in the areas of many-body theory of phonon-induced optical decoherence in QDs, quantum optics and QD-cavity quantum electrodynamics. In this project, coherent coupling and coherent control of remote QDs via optical resonators in optical circuits will be investigated. Such QDs play the role of isolated qubits, and their controlled coupling is of paramount importance for quantum technology applications. You will be calculating the excitonic absorption and photoluminescence in QDs coupled to optical cavities and waveguides, as well as the Purcell enhancement of their emission. You will be studying theoretically fundamental mechanisms of the acoustic-phonon induced dephasing and the Foerster transfer in electronically decoupled quantum dots with account for the acoustic-phonon environment. You will be using various methods of many-body theory including diagram techniques, density matrix approach with Lindblad dissipators, Trotter's decomposition, matrix cumulant expansion and so on. The project is embedded in a bigger EPSRC funded research activity at Cardiff School of Physics and Astronomy and will benefit from a close collaboration with an experimental research team working on the controlled long-range coherent coupling of quantum dots via cavities. Comparing theory with measured optical data, fundamental mechanisms of the coherent coupling will be understood and important parameters of the experimentally investigated systems will be extracted for predictive modelling of QDs embedded in complex quantum circuits. Our scientific excellence in this field is confirmed by research publications on this topic in Nature group journals: Nature Mater. 9, 304-308 (2010) and Nature Commun. 4:1747 (2013), as well as by the most recent theoretical work providing an exact solution of a long-standing fundamental problem of the phonon-induced decoherence of the QD-cavity system: arXiv:1807.10977 (2018).Feasibility: The work on the project will be a balanced combination of both analytical and numerical methods and will consist of the following stages: (i) Studying literature and theoretical methods, solving introductory training problems (yr 0-0.5); (ii) Calculating coherent coupling and control of remote QDs, drafting research papers (yr 0.5-2.5); Writing up thesis and presenting at conferences (yr 2.5-3.5).