Quantum Light with Quantum Dots in III-V Photonic Integrated Circuits: Towards Scalable Quantum Computing Architectures

The work in this thesis is motivated by the goal of creating scalable quantum computers, and equally by the physical understanding that develops alongside and follows from this. The fields of physics and technology are symbiotic, and quantum information processing is a prime example. The field has the potential to test quantum mechanics in new and profound ways. Here we approach the technological problem by building upon the foundations laid by the semiconductor chip manufacturing industry. This architecture is based on the III-V semiconductors Gallium Arsenide and Indium Arsenide. Combining the two we can create chip-embedded atom-like light sources -- quantum dots -- that can produce quantum photonic states in lithographically etched nanoscale waveguides and cavities. We demonstrate the integration of quantum light sources and single-mode beam splitters in the same on-chip device. These are the two primary ingredients that are needed to produce the entangled states that are the basis of this type of quantum computing. Next we look at the quantum light source in more detail, showing that with cavity-enhancement we can significantly mitigate the detrimental dephasing associated with nanostructures. The source can be used as a means to produce coherently scattered photons in the waveguides. More importantly, the on-demand photons obtained from pulsed excitation are more indistinguishable and thus more suitable for quantum information carrying and processing. Through experiments and simulations, we investigate some aspects of single-photon sources under pulsed excitation, including emission rate, emission number probabilities, and indistinguishability. A new technique to measure very short lifetimes is demonstrated and examined theoretically. Finally we look at preliminary steps to extend the platform further. The inclusion of photonic crystals and superconducting nanowires provides on-chip filters and detectors, and etched diode structures enable electrical excitation and tunability of the circuit components. These show some clear paths that the work can continue to evolve along.