New light sources for quantum information processing

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Outstanding research in quantum information processing over the past two decades highlights its potential for practical applications and deeper insights into quantum mechanics. This thesis centers on the photon as a key resource for quantum information tasks, focusing on imprinting quantum bits onto its various degrees of freedom. The photon's weak coupling to the environment makes it ideal for secure information transmission via quantum cryptographic protocols. Efficient quantum computing implementations using linear optics have been established, but scalability remains a challenge due to the difficulty in generating indistinguishable single photons from multiple emitters. Proposed quantum networks incorporate single photons as carriers between atomic ensembles, which serve as storage and processing nodes. The thesis begins with the generation and characterization of single-photon states from a single optically pumped quantum dot, demonstrating their capability to implement a quantum algorithm through linear optics and single-photon interference. Error correction enhances the robustness of the interferometric setup against phase noise. The need for compact, low-cost single-photon sources for quantum key distribution is addressed, presenting an electrically pumped quantum dot source with exceptional spectral purity. Subsequent chapters detail the generation of narrow-band single photons that efficiently couple to atomic resona