Taking Light to the Next Level: Harnessing High-Dimensional Entanglement for Quantum Photonic Technologies

This seminar will be followed by coffee and biscuits in the DB crush area.

Abstract
The spatial and temporal structure of photons allows us to study complex quantum systems such as high-dimensional and multipartite entangled states of light. These serve as test beds for quantum foundations and are simultaneously powerful platforms for overcoming current limitations of quantum technologies based on binary (qubit) encoding. This thesis presents practical demonstrations of the generation, characterisation, measurement, and transport of high-dimensional photonic entanglement. We develop techniques for the precise measurement and efficient certification of entangled states in the Laguerre-Gaussian and the discrete position-momentum (pixel) bases, demonstrating high-dimensional entanglement with record quality, measurement speed, and entanglement dimensionality. Additionally, we tackle the challenge of transporting high-dimensional entangled states by unscrambling pixel entanglement after transmission through a complex scattering channel consisting of a commercial multi-mode fibre. Finally, we program optical circuits inside a multi-mode fibre to observe quantum interference between two independent photons inside a complex medium, demonstrating the potential of this platform in the control of high-dimensional multipartite entanglement. These results bring us closer to realising high-capacity quantum networks that operate under realistic and noisy environments, and open a new pathway towards the control of complex scattering processes for technologies based on multimode entanglement