Phd Defense: Patrik Isene Sund

Photonic quantum information processing with quantum dot single-photon sources

The fundamentally quantum mechanical properties of single photons present an exciting opportunity for the development of new technology. The fragile nature of quantum states makes this a challenging prospect, pressing stringent demands on the hardware used to generate and process the light. In this context, semiconductor quantum dots are emerging as a promising platform, enabling the realization of highly-efficient sources of near-identical single photons. In this work, we aim to expand the capabilities offered by these sources and state-of-the-art photonic technology. We present novel specialized interferometer architectures developed for the time-bin encoding naturally produced by quantum-dot single-photon sources (SPSs), that allow for significant reductions in loss. We proceed to leverage the advantageous properties of the time-bin encoding by constructing a resource-efficient interferometer used in an experimental demonstration of bosonic suppression laws and postselected entanglement using photons emitted from a quantum-dot SPS. Shifting the focus to photonic integrated circuits, we design a lithium-niobate-on-insulator (LNOI) chip tailored to the emission wavelength of our quantum dots. We perform two-photon interference experiments on two-mode and four-mode interferometers, carrying out the first demonstration of the Hong--Ou--Mandel effect on LNOI. Furthermore, we leverage the fast electro-optic modulators on LNOI to realize an on-chip demultiplexer, which is used to demonstrate active demultiplexing of the single-photon source. Finally, we extend the scope to larger scales by analyzing the hardware requirements for a quantum advantage demonstrations using the boson sampling algorithm with photons emitted from a quantum-dot SPS, determining it to be within reach for current state-of-the-art hardware.