Traditional analysis of light propagation in a medium is based on more than a century-old theories of electrodynamics of a continuous polarizable medium and its consequences such as standard optics. In cold and dense atomic gases such theories can qualitatively fail. This is because light mediates strong interactions between the atoms that establish correlations between the positions of individual atoms in the cloud. In this project we theoretically study light propagation in cold and dense atomic ensembles. The work will be done in a close collaboration with experimental groups who trap cold and dense atomic gases in laboratories. The goal is to utilize the strong light-mediated interactions in the design of better atomic systems for high-precision measurements. Improved detection techniques could, for instance, lead to more accurate time measurements, better satellite navigation and better lasers.

Light has been used for centuries to image the world around us, and continues to provide profound insights across physics, chemistry, biology, materials science and medicine. However, what are the limits of light as a measurement tool? For example, we can use light to image single bacteria, but can we also use light to trap a single bacterium, identify the bacterial strain and assess its susceptibility to antibiotics? How can we image over multiple length scales, from single cells to multiple cellular tissue, in order to comprehensively map all the neuronal connections in the brain? Can we use a combination of resonance with the wave nature and momentum of light to measure the forces associated with the natural and stimulated motion of a single neuronal cell, or even the extremely small forces associated with phenomena at the classical-quantum interface? This proposal aims to answer these questions by exploring new and innovative ways in which we can use light to measure the natural world. This research builds on our recent advances in photonics - the science of generating, controlling and detecting light - and in particular will exploit resonant structures and shaped light. These provide us with tools for controlling the interaction of light and matter with exquisite sensitivity and accuracy. We will run three research strands in parallel and by combining their outputs, we aim to address major Global Challenges in antimicrobial resistance, neurodegenerative disease, multimodal functional imaging and next generation force, torque and microrheology. Our work is supported by a suite of UK and International project partners (both academic and industry) who are enthused to work with us and have committed over £0.5M in kind to the programme.