Investigation of quantum measurement and feedback in multipartite quantum systems of ultracold atoms

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This project will utilise experimental apparatus that has been constructed to produce quantum gases of rubidium atoms at temperatures of tens of nanokelvin. Specific experimental techniques that have been developed by the research team in Oxford include the confinement of atoms in potentials formed by a combination of static and radiofrequency magnetic fields. These allow highly controllable manipulation of the system to make a double-well potential and also to change the dimensionality of quantum gas between three and two. Special properties of rubidium atoms make them amenable for work with superpositions of internal states (in different hyperfine levels) as well as mixtures of their external quantum states in multiple potential wells. When this apparatus has been fully characterised, its unique capabilities will be used to investigate a wide range of phenomena in many-body quantum systems. Specific goals will be to investigate non-classical states of these multipartite systems arising in quantum feedback schemes in which the results of a weak (non-destructive) quantum measurements are used to control the state of the system. Such states enable precision measurements going beyond the Standard Quantum Limit, however the emphasis in this project will be on the influence of quantum feedback on the collective properties in this new regime. Work with rubidium (with the possibility of using mixtures of different states) will be provide more than sufficient results for a doctorate but this work can be extended to multiple atomic species such as rubidium and strontium, contingent on further funding. There is a large scope for theoretical work associated with the new possibilities arising from this work and we will continue to collaborate with theoreticians who are developing novel ideas in this field.