Direct quantum simulation using cold bosonic atoms in an optical lattice

我们将发展利用光学晶格中的超冷玻色子原子对凝聚态系统进行直接量子模拟的实验技术，分为目标标题下列出的五个阶段。第一阶段已经在牛津实现，使用的是磁捕获器中的蒸发冷却，但通过改用光学偶极捕获器，我们将更快地获得BEC，并加快数据采集。我们计划在任何授权期开始之前在第二阶段取得实质性进展，特别是在冷原子位置上安装高数值孔径透镜(NA=0.8)，其光学分辨率优于1微米。为了确定地在光学晶格势的每个势垒中制备单个原子，我们将使用基于Feshbach共振的方案(我们以前在牛津大学研究过)；在特定磁场下原子之间相互作用的共振增强防止在同一个势垒中有不止一个原子。在第四阶段，我们将使用慕尼黑实验演示的方法实现邻近位置上原子之间的自旋相关相互作用(并继续与牛津的Dieter Jaksch博士和他的团队合作探索改进的方法)。利用拉曼跃迁对原子波函数施加相移，模拟了外加磁场对凝聚态系统的影响。光学晶格中每个原子的最终量子态将由荧光决定，就像在离子陷阱中一样。一旦用玻色子发展了直接量子模拟的方法，并证明给出了重要的结果，我们就可以将它们扩展到费米子原子(例如钾-40)，从而研究更广泛的凝聚态系统。

We shall develop the experimental techniques for direct quantum simulation of condensed matter systems using ultra-cold bosonic atoms in optical lattices, in the five stages listed under the Objectives heading. Stage 1 has already been achieved in Oxford using evaporative cooling in a magnetic trap but by changing to an optical dipole trap we shall obtain BEC more quickly and speed up data taking. We plan to have made substantial progress towards stage 2 by the start of any grant period, in particular to have a high numerical aperture lens (NA=0.8) in place that gives an optical resolution of better than 1 micron at the position of the cold atoms. To deterministically prepare a single atom in each well of the optical lattice potential we shall use a scheme based on Feshbach resonances (that we have previously studied in Oxford); resonant enhancement of the interaction between atoms at a certain magnetic field prevents there being more than one atom in the same well. In stage 4, we shall implement spin-dependent interactions between atoms in neighbouring sites using a method demonstrated experimentally in Munich (and continue to explore improved methods in collaboration with Dr Dieter Jaksch and his group in Oxford). The effect of an external magnetic field on a condensed matter system is simulated by imposing a phase shift on the atomic wave functions using Raman transitions. The final quantum state of each of the atoms in the optical lattice will be determined by fluorescence as in ion traps. Once methods for direct quantum simulation have been developed with bosons, and shown to give important results, we can extend them to fermionic atoms (e.g. potassium-40) and so study an even wider range of condensed matter systems.