Theory and Modelling of Pulse-Driven Quantum Dots in Nanophotonic Structures

Abstract

Quantum dots (QDs) integrated in nanophotonic environments provide an excellent platform for quantum information technologies and engineerable light-matter interactions. One application is a solid-state single photon source (SPS), where a QD in an optical cavity can be used to emit antibunched photons. This setup can provide photons on-demand if excited with a pulse, which renders the problem of modelling the QD SPS a genuinely time-dependent problem in quantum optics. Furthermore, the QD-cavity system interacts with its environment via electron-phonon scattering with the surrounding lattice as well as coupling to the photonic background, which causes decoherence and necessitates an open quantum system framework. In this thesis, we study pulse-driven QDs coupled to photonic environments and phonon reservoirs using an open system quantum optics approach, with a focus on elements unique to the time-dependent dynamics. After introducing the necessary theoretical background, first we present an analysis of the impact of electron-phonon scattering on a proposal for a QD-cavity system which uses adiabatic passage to generate triggered single photons of orthogonal polarization to the excitation fields. Next, we provide an analysis of the resonance fluorescence spectrum of two-level systems (including QDs) driven by a pulse, with particular emphasis on where spectral asymmetries can arise. Last, we study resonantly excited QD-cavity SPSs with attention given to how the excitation pulse can affect the quantum dynamics and SPS figures-of-merit. We show that the excitation process can degrade the figures-of-merit to a degree comparable to the electron-phonon interaction. We also find that a dynamical decoupling effect between the QD and its environment plays a large role in suppressing multi-photon emission, and we demonstrate how this effect can be modelled by using a time-dependent and time-convolutionless quantum master equation which incorporates non-Markovian effects associated with the pulse. These findings have implications on both the theoretical understanding of pulsed QD light-matter interactions, as well as on how SPSs can be optimized.