Generation and characterization of entangled states of light in a silicon nitride microresonator

Developing quantum devices with high generation rates, small sizes, and robust operation is a mandatory requirement in the research toward a fully working quantum network and quantum internet. The integration of light sources into photonic integrated circuits is a novel and promising approach to such a problem. In this thesis, we detail the generation and characterization of entangled states of light in an integrated Si3N4 microresonator. The goal is to develop on-chip single- and entangled-photon sources compatible with the telecom band, utilizing third-order nonlinearity. To provide a clearer characterization of the light generated by the microresonator, we first present a metrological study of the detection efficiency of SNSPDs. We also performed an innovative measurement that quantifies the dependence of the detection efficiency on the light polarization. The central device is a silicon nitride microring with a nominal quality factor of about one million. Photon pairs are generated via Spontaneous Four-Wave Mixing (SFWM) below the OPO threshold. Semiclassical results include a photon-pair generation rate of 316(3) kHz/mW^2 and a maximum CAR of 3.6(3) for modes. The intrinsic heralding efficiency reached 0.862(5), demonstrating a strong correlation. Quantum metrics include confirming individual modes exhibit super-Poissonian statistics, and demonstrating non-classical temporal correlations by violating the Cauchy-Schwarz inequality for multiple modes. The latter is the first hint of quantum entanglement, but it is not enough to demonstrate it. Time-energy entanglement was proven via Franson interference, yielding an average visibility of V = 84(3)%, above the 70.7% quantum threshold. The microring was also validated as a heralded single-photon source with heralded second-order correlation of 0.113(10), compatible with a single photon state. Lastly, we present experimental results displaying the dependence of the emitted photons' bandwidth as a function of the operational regime. Tuning the circulating power effectively tunes the detuning with the pumped resonance. It is possible to modify the photon's bandwidth over three orders of magnitude (from about 100 MHz to 30 kHz). The latter results are innovative and not present in literature as of the writer's knowledge, and can be important, allowing the device to integrate with different quantum devices that exhibit diverse photon bandwidth requirements.