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Abstract
This thesis deals with quantum dot (QD) based single-photon sources (SPSs) for applications in quantum information processing (QIP). While primarily theoretical, the thesis also features some experimental results. To account for optical effects, we employed the Fourier modal method (FMM) with open boundary conditions combined with a standard scattering matrix formalism, enabling us to compute the collection efficiency of rotationally symmetric configurations. For mechanical effects, we used a finite element method (FEM) software to determine the eigenmodes of geometries under given boundary conditions. Here, we investigate the mechanisms influencing the performance of SPSs in the presence of lattice vibrations, focusing on phonon-induced decoherence and its impact on the photon indistinguishability. First, we address phonon-induced dephasing in semiconductor QDs in a one-dimensional homogeneous cylindrical nanowire. From a polaron approach, we derive an analytical expression for the 1D pure dephasing rate, resulting in a reduction compared with 3D bulk media. Our findings emphasize the necessity of multimode coupling in accurately predicting the indistinguishability within 1D systems, as well as the potential of harnessing non-Markovianity to enhance coherence properties. Following, we assess the impact of thermal vibrations on the photonic “hourglass” structure, revisiting the previous design for near-unity efficiency and indistinguishability while now providing a more suitable treatment of phonons. Our detailed incorporation of vibrational modes demonstrates the structure’s robustness, attributed to significant Purcell enhancement, which mitigates phonon decoherence effects and preserves close-to-unity indistinguishability. We then analyze an optimized nanopost nanocavity SPS design, achieving photon indistinguishability of I = 0.977 for a QD in the center at the second antinode of the geometry at 4 K, underscoring the potential of this design for scalable quantum photonic applications. Finally, we investigate phonon signatures revealed by the excitonic emission from nanowire QDs and atomically thin 2D semiconductors, i.e., WSe2 quantum emitters (QEs). Our results highlight the impact of residual dephasing mechanisms, such as charge and spin fluctuations, on the photon indistinguishability, demonstrating the importance of countering such effects to improve the performance of solid-state QEs. Overall, this thesis provides critical insights into the interplay between phonon dynamics and SPS performance, offering pathways to optimize the indistinguishability and efficiency of quantum photonic devices.
Original language | English |
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Publisher | Technical University of Denmark |
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Number of pages | 166 |
Publication status | Published - 2024 |
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Dive into the research topics of 'Quantum Light Sources in Phononic Environments'. Together they form a unique fingerprint.Projects
- 1 Finished
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Optomechanics with Quantum Emitters
Ferreira Neto, J. (PhD Student), Gregersen, N. (Main Supervisor), Vannucci, L. (Supervisor), Iles-Smith, J. (Examiner) & Sørensen, A. S. (Examiner)
15/01/2021 → 02/12/2024
Project: PhD