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Until recently, quantum photonic architecture comprised of large-scale (bulk) optical elements, leading to severe limitations in miniaturization, scalability and stability. The development of the first integrated quantum optical circuitry removes this bottleneck and allows realization of quantum optical schemes whose greatly increased capacity for circuit complexity is crucial to the progress of experimental quantum information science and the development of practical quantum technologies. Integrated quantum photonic circuits within Silica-on-Silicon waveguide chips were simulated, designed and tested. Hundreds of devices have been fabricated with the core components found to be robust and highly repeatable. Amongst these demonstrations, all the basic components required for quantum information applications are shown. The first integrated quantum metrology experiments are demonstrated by beating the standard quantum limit with two- and four-photon entangled states while providing the first re-configurable integrated quantum circuit capable of adaptively controlling levels of non-classical interference of photons. The tested integrated devices show no limitations to obtain high quality performances. It is reported near-unity visibility of two-photon non-classical interference and a Controlled-NOT gate that could in principle work in the fault tolerant regime. It is demonstrated the realization of a compiled version of Shors quantum factoring algorithm on an integrated waveguide chip. This demonstration serves as an illustration to the importance of using integrated optics for quantum optical experimentsThe first integrated optical circuits fabricated in the laser direct-write technology are reported in this Thesis. The quality quantum effects, together with a rapid turnaround process and the capability of writing complex 3D structures are promising for future quantum optical networks. The advent of integrated quantum photonics is necessary for the progression of quantum information science. The results reported in this Thesis provides fundamental building blocks from which future quantum devices will be constructed and presents high-fidelity quantum optics platforms for fundamental investigation

Since the discovery of peculiar phenomena in the nano-world, at the beginning of last century, our understanding of nature at this level has being constantly improving through the establishment of quantum theory. A plethora of benefits has already been exploited in semiconductors, paving the way for the age of electronics. Despite the new, groundbreaking developments, this wasn't but the first step on the spectrum of capabilities the quantum world could offer us. The second step that will follow is about quantum technologies exploiting the very nature of quantum physics and embracing these counter-intuitive phenomena to harness an advantage over the so far, classical operation of electronics. On this route, there are many challenges still remaining, with scalability being the toughest. Our approach to tackle this issue, is to have all components needed integrated on chip, on a fabrication friendly material. Moreover, this material has to host quantum emitters which should be easily and reliably being controlled. Such a material is silicon carbide since it's been used for decades by the high power electronics industry while at the same time, colour centres in silicon carbide have been shown to have a high level of familiarity with the NV− centre in diamond. We aim on developing fabrication techniques that will allow us to have a reliable platform for quantum technologies. We aim on fabricating high quality factor photonic crystal cavities with embedded colour centres which would deliver high Purcell factors. Purcell factor's importance would become prominent as we demonstrate its connection with two of the most important parameters for quantum technology applications, namely the indistinguishability and the emitter-photon coupling efficiency. Our high level of fabrication fidelity, allows us to fabricate complex cavity designs with high Q/V ratios. A simulated photonic crystal cavity design in SiC of Q/V ∼ 500, 000(n/λ) 3 will be presented and fabricated. The homebuilt confocal microscopy setup will be described in detail and its abilities will be manifested. Using this setup, we are able to measure photonic crystal cavities with Q factors as high as 7138, the highest reported in 3C-SiC. Such cavities could yield a Purcell factor of 443 and consequently indistinguishability could reach to 0.85 with coupling efficiencies of 0.97. Further efforts have to be made to characterise these parameters, as preliminary work has been made to implant colour centres in photonic crystal cavities.

The work presented in this thesis aims to integrate sources and detectors of nonclassical states of light into a single photonic chip. Correlated pairs of single photons are among the most used sources in many quantum optics and quantum information experiments but their integration with detectors still remains a challenging task. In the first part of the thesis we exploit the generation of correlated pairs of photons in the visible spectrum using an integrated Silicon Nitride microring resonator. As the fabrication process of our sources is fully compatible with back-end CMOS technology, we also discuss the unique possibility of integration with silicon avalanche photodectors to provide a platform for commercially available, fully integrated, analogue quantum simulator working at room temperature. The drawback of universal quantum computation with single photons is its probabilistic nature that increases the technological complexity to obtain complete on chip integration of all necessary components to prepare, manipulate and measure quantum states of light. On the other hand, quantum information processing with continuous variables is completely deterministic. Therefore, in the second part of this work we report design, fabrication and experimental verification of an integrated source of broadband squeezed state of light on a photonic chip. We numerically investigate the amount of obtained squeezing and spurious noise that prevents us to observe shot noise reduction at short sideband frequencies. Additionally, we propose a design to extend our work towards hybridization with discrete variables to obtain qubits that can be protected against errors.

Quantum information sciences offer novel capabilities in the fields of computation, data security and sensing. In order to deliver these improvements, information needs to be encoded in a physical quantum system the realization of which is technologically challenging. Even though several platforms have been proposed for computation, quantum information encoded in nonclassical states of light is going to play a central role since the classical fiber technology already provides an almost ideal transmitting medium. Furthermore, a hybrid approach formed together with solid state emitters could meet the non-trivial requirement needed for quantum computation. In the past ten years, efforts have been placed in integrating the bulky optical components required to manipulate nonclassical states of light, giving birth to the field of quantum photonics. Between all the different materials proposed, 3C silicon carbide (SiC) meets all the complex requirements needed for photonic quantum technologies and the development of essential components to this scope is the main subject of this thesis. The design, fabrication and characterization of small modal area waveguides, grating couplers and ring resonators made in SiC are reported. Four wave mixing was demonstrated thanks to the small modal volume achieved in the ring resonator and the Kerr coefficient of SiC was retrieved. The realization of photonic crystal cavities is also investigated with the aim to harness quantum emitters. Thanks to the demonstration of coupling between confined and propagating surface waves, SiC is a potential platform for quantum applications in the mid-infrared. Finally, the generation of photon pairs in the near-infrared by means of third order nonlinear process is reported using ring resonators fabricated in silicon nitride.