NSF-BSF: Rotating Ultracold Fermi Gases in a Box

长期以来，旋转容器中流体的行为一直是基础流体力学和应用流体力学的一个重要课题，包括湍流的研究。当日常-经典-流体缓慢地旋转时，它们显示出众所周知的渐进旋转运动。对量子流体旋转的反应则截然不同。低于一定的旋转频率，这些流体对容器的旋转没有反应；如果它们旋转得足够快，就会出现被称为漩涡的漩涡。这些漩涡具有明显的量子特性，是理解量子流体流体动力学的关键。特别是，量子流体的湍流是由涡旋之间的相互作用以及涡旋激励与声波之间的相互作用所主导的。研究量子流体中的湍流的主要动机之一是，由于量子漩涡的离散定义良好的性质，它比经典流体中更常见的湍流更基本，并且可以为后者的理解提供蓝图。这个项目将通过使用超冷原子气体作为量子流体来解决这个问题。这些气体将被困在由光制成的盒子里，用可编程的电光设备雕刻。利用这些装置的快速实时特性，将超冷气体置于旋转状态，研究量子化涡旋的成核及其激励。在量子物质上投射几乎任意的“电影”的能力将预示着量子控制的一个新阶段，并为可编程量子模拟提供了额外的一步。本项目将支持培训两名研究生掌握原子物理的现代技术和光对量子物质的通用控制。均匀量子气体最近被证明是一种令人兴奋的新型量子流体，具有明显的优势。这个项目将结合这些新颖的均匀气体和原子陷阱的实时控制来研究教科书设置中的超流体方面。本项目将使用光盒捕获气体来研究强相互作用量子流体中超流动性的开始和涡旋细丝的集体激发。尽管进行了大量的实验和理论研究，但关于超流体的几个基本问题仍然很突出。其中一个平衡问题是强相互作用超流体中超流体密度、序参量和凝聚分数之间的关系。第二个非平衡的例子是作用在涡流上的力的问题。这些力对量子流体的超流体和正常组分之间的相互摩擦以及涡旋的质量都有至关重要的影响。这种力量的计算是有争议的。这个项目将研究亚临界和超临界旋转的状态。将产生非平衡三维单涡状态，并用于研究涡旋的惯性质量问题和涡旋细丝的各种集体激励的性质。Gross-Pitaveskii和Bogoliubov-de Gennes方程的数值模拟将通过测试光学箱中的旋转协议以及激发和探测涡旋集体激发的机制来指导实验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The behavior of fluids in rotating containers has long been a crucial topic in both fundamental and applied hydrodynamics, including in the study of turbulence. When everyday – classical - fluids are slowly set in rotation, they display a well-known progressive rotation motion. The response to rotation of quantum fluids is strikingly different. Below a certain rotation frequency, these fluids do not respond to the rotation of their container; if they are rotated sufficiently fast, swirling eddies called vortices appear. Those vortices have distinctly quantum properties, and are key to understanding the hydrodynamics of quantum fluids. In particular, the turbulence of quantum fluids is dominated by the interactions between vortices, and by the interactions between excitations of vortices and sound waves. One of the main motivations in studying turbulence in quantum fluids is that, because of the discrete well-defined nature of quantum vortices, it is more fundamental than the more common turbulence of classical fluids and could provide a blueprint for the understanding of the latter. This project will tackle this topic by using gases of ultracold atoms as quantum fluids. These gases will be trapped using boxes made of light, carved using programmable electro-optic devices. Exploiting these devices’ fast real-time characteristics, the ultracold gases will be set in rotation and the nucleation of quantized vortices and the excitations of these vortices will be studied. The ability to project nearly arbitrary “movies” on quantum matter will herald a new stage in quantum control and provide an additional step towards programmable quantum simulation. This project will support the training of two graduate students to modern techniques in atomic physics and the versatile control of quantum matter with light.Uniform quantum gases have recently proven to be an exciting new class of quantum fluids, with distinct advantages. This project will combine these novel uniform gases and real-time control of the atom traps to study aspects of superfluidity in textbook settings. This project will use optical-box trapped gases to study the onset of superfluidity in strongly interacting quantum fluids and the collective excitations of vortex filaments. Despite extensive experimental and theoretical efforts, several fundamental issues about superfluidity remain outstanding. One such equilibrium problem is the relation between superfluid density, the order parameter and the condensed fraction in a strongly interacting superfluid. A second, out of equilibrium, example is the problem of the forces acting on a vortex. Those forces have crucial consequences on the mutual friction between the superfluid and normal components of quantum fluids and on the mass of a vortex. The calculation of such forces is notably controversial. This project will investigate both the regime of sub-critical and supercritical rotation. Off-equilibrium three-dimensional single-vortex states will be produced and used to investigate problems of the inertial mass of a vortex and the nature of various collective excitations of vortex filaments. Numerical simulations of the Gross-Pitaveskii and the Bogoliubov-de Gennes equations will guide the experiments by testing rotation protocols in optical boxes as well as mechanisms to excite and probe the collective excitations of the vortices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.