Optical Hybrid Architectures For Quantum Information Processing

The thesis focuses on the experimental investigation of the optical hybrid approach for quantum information processing. Specifically, two traditionally separated approaches, i.e. the discrete and the continuous-variable ones, are combined in the same experiment with two distinct quantum measurements based on photon counting (photon number) and homodyne detection (quadrature components).The optical hybrid approach is first applied to generate high-fidelity non-Gaussian states, e.g. Fock states and Schrodinger cat states, which correspond to two types of qubit encodings used in optical quantum information. The use of high-efficiency superconducting nanowire single-photon detectors leads to an unprecedented preparation rate, which facilitates the subsequent use of these states. For instance, the two types of states are combined to generate for the first time a hybrid entanglement between particle-like and wave-like optical qubits, as well as the extension to hybrid qutrit entanglement. These novel resources may pave the way to implement heterogeneous networks where discrete and continuous-variable operations and techniques can be efficiently combined. Additionally, we also experimentally demonstrate for the first time the so-called squeezing-induced micro-macro entangled states.During this PhD, efforts have also been dedicated to implement a high-efficiency and low-noise frequency up-conversion system based on two synchronized fiber lasers. Such quantum frequency converter not only permits to extend the spectra of quantum states to difficultly accessible wavelengths with current technology, but also constitutes a high-performance photon detector especially in the infrared regime. Based on the conversion system, several applications are demonstrated, such as infrared photon-number-resolving detection, and few-photon-level infrared imaging.