UCLA

Single photons are flying qubits which can carry quantum information over long distances with low decoherence. Integrated quantum photonics, which aims to generate, process, and detect single photons on tiny chips with minimum environment-induced decoherence essential for quantum information processing, has become the core of current quantum technology towards quantum computing, quantum communication, and quantum metrology. Such applications require material platforms which can support single photon emitters with suitable properties, such as high single-photon purity, lifetime-limited spectral linewidth. high indistinguishability, near-unitary state preparation efficiency, and near unitary quantum efficiency, etc. Decoherence induced by environmental charge fluctuation and phonon scattering are also important factors to be considered in semiconductor-based platforms. In addition, site controllability of single photon emitters to be placed at the designed location is required for reproducible fabrication of monolithic integrated quantum photonic devices in large scale with multiple single photon emitters. On the other hand, single photon emitters in the telecom band are beneficial for building metro scale quantum networks such that the computational power of induvial quantum processors can be scaled up using telecom fiber-based architecture. Site-controlled pyramidal InGaAs quantum dots system as single photon emitters enable placing many quantum dots at designed positions in photonic structures with nanometer scale precisions which provides great potential for large scale integrated quantum photonic devices. However, previous studies on such quantum dots embedded in photonic crystal cavities suffer from low cavity quality factor which limits its operation at the weak coupling regime. In this thesis, we improve the cavity quality factor up to 12,000 by red shifting the emission energy of the quantum dot to ~ 1.24 eV and optimizing the photonic crystal cavity design. We demonstrate the coexisting strong-weak (intermediate) coupling and onset of strong coupling regime. We reveal the role of phonon scattering and exciton dephasing during QD-cavity interactions and further demonstrate a Rabi-like oscillation of luminescence intensity and energy splitting between excitonic and photonic components which occurs only at small QD-cavity detuning and can be well reproduced by our cavity quantum electrodynamics modeling. It represents milestone for device optimization of such quantum dot systems to realize strong coupling regime with applications in coherent control of site-controlled quantum states for quantum information processing. We further explore multi-site-controlled quantum dots systems in a spatially extended cavity mode pattern such that the quantum dot emission exhibits novel spatial features linked to quantum mode interference which enables applications in optical switching for quantum information routing in monolithic integrated quantum photonic circuits. This thesis also explores using silicon color centers as single photon emitters considering its telecom emission wavelength and mature silicon-based integrated photonic and electronic platform. We explore T centers and transition-metal color centers for high-fidelity telecom spin-photon interfaces. We study the fabrication process of generating T centers and copper-related defects with reduced lattice distortion with their photophysics properties closer to ab initio calculations. The cryogenic photoluminescence and electron spin resonance studies on copper-related defects suggests its unpaired electrons as alternative candidates to T centers for high fidelity spin-photon interfaces.