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

该项目将利用已经建造的实验装置，在数十纳开尔文的温度下产生铷原子的量子气体。牛津大学研究小组开发的具体实验技术包括将原子限制在由静态和射频磁场组合形成的电势中。这允许高度可控的系统操作，以产生双阱势，并在三到二之间改变量子气体的维数。铷原子的特殊性质使它们适合于在多个势威尔斯中进行内部态（在不同的超精细能级上）的叠加以及外部量子态的混合。当这个装置被充分表征后，它独特的能力将被用来研究多体量子系统中的各种现象。具体的目标将是调查这些多体系统中产生的量子反馈方案，其中弱（非破坏性）量子测量的结果被用来控制系统的状态的非经典状态。这种状态使精确测量超过标准量子极限，但在这个项目的重点将是量子反馈对集体性质的影响，在这个新的制度。铷的工作（有可能使用不同状态的混合物）将为博士学位提供足够的结果，但这项工作可以扩展到多个原子物种，如铷和锶，取决于进一步的资金。有一个很大的范围，理论工作与新的可能性，从这项工作中产生的，我们将继续与理论家谁是发展新的想法在这一领域的合作。

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.