Quantum Vortex Laboratory: Generation, Manipulation, Imaging, and Dynamics of Vortices in Bose-Einstein Condensates

在高速下，流体流过一个物体或流过一个管道会导致湍流，这是一种以不可预测的涡流或涡流运动为特征的混乱流动状态。湍流无处不在，通常在飞机或船只上经历，在湍急的河流中观察到，也可能存在于血液流动中。然而，尽管对湍流进行了几个世纪的研究，但这种流体流动状态是物理学中最不为人所知的现象之一。发现它的物理起源，并充分表征它的动力学和平滑和湍流之间的过渡，仍然是物理学的重大挑战。克服其中一些问题对于深入了解宇宙的许多方面是如何演变的至关重要。这个由美国国家科学基金会资助的项目通过实验解决了一种特殊类型流体中与湍流有关的流体流动问题，理论和分析方法已经得到了发展。在这些被称为玻色-爱因斯坦凝聚体（BECs）的流体中，微小的气体液滴冷却到绝对零度以上几十亿分之一度的温度，激光可以精确地产生、操纵和观察湍流以及构成湍流的漩涡的动力学。通过测试理论预测，该项目推动了我们对流体动力学特征的理解，因为它们出现在bec中，推进了对湍流的理解，这些湍流建立在物理学家用来描述宇宙、其结构和动力学的最基本框架之上。该项目的主要科学目标是发展对超流体BECs（量子力学控制流体流动动力学的超流体）中量子化涡旋动力学的完整理解。为实现这一目标，采取了多方面的办法。首先，该项目建立在先前工作的基础上，建造了一个最先进的显微镜，专门用于直接观察和测量bec中的涡旋及其动力学。其次，通过研究激光搅拌二维BEC时产生的涡流，研究了BEC向湍流的过渡。结果验证了关键的理论结果，并有助于建立量子流体和经典流体之间的联系。第三，继续构建BEC中按需创建和操纵漩涡的工具包，以先前成功的方法为基础，使用移动激光束产生和操纵漩涡，以便在量子流体动力学实验中按需创建和使用漩涡的特定排列或流体流动类型。最后，为了更全面地了解涡旋和湍流流体流动如何在BECs中产生，研究了新观察到的涡旋成核方法。通过探索BEC涡旋的动力学，这项工作促进了对具有不同微观性质系统（如超流体、超导体和中子星核心）中量子多体现象的更广泛理解。该项目依托和促进学生的科学教育和技术培训，这是保持国家科学实力和社会广度和创造力的关键。

At high speeds, fluid flow past an object or through a tube results in turbulence, a chaotic state of flow characterized by unpredictable motion of the vortices or eddies of the flow. Turbulence is ubiquitous, commonly experienced in aircraft or watercraft, observed in rushing rivers, and may be present in blood flow. Yet despite centuries of research on turbulence, this state of fluid flow is one of the least understood phenomena in physics. Discovering its physical origins, and fully characterizing its dynamics and the transition between smooth and turbulent flows, remain significant challenges in physics. Overcoming some of these problems is essential for reaching a deeper understanding of how numerous aspects of our universe evolve. This NSF-funded project experimentally tackles aspects of fluid flows related to turbulence in a special type of fluid for which theoretical and analytical approaches have been developed. In these fluids, called Bose-Einstein condensates (BECs), microscopic droplets of gases cooled to temperatures of a few billionths of a degree above absolute zero, laser light can precisely generate, manipulate, and observe turbulence and the dynamics of the vortices that comprise turbulence. By testing theoretical predictions, this project pushes the boundaries of our understanding of these features of fluid dynamics as they appear in BECs, advancing an understanding of turbulence built up from the most fundamental framework that physicists use to describe the universe, its structure, and its dynamics.The primary scientific aim of this project is the development of a complete understanding of quantized vortex dynamics in BECs, superfluids for which quantum mechanics governs the dynamics of fluid flow. To achieve this aim, a multi-faceted approach is pursued. First, the project builds on previous work to construct a state-of-the-art microscope designed for and dedicated to observing and measuring vortices and their dynamics directly in BECs. Second, the transition to turbulence in a two-dimensional BEC is studied by examining vortex generation as BECs are stirred by laser light. Results test key theoretical results, and help establish links between quantum and classical fluids. Third, the construction of a toolkit for on-demand creation and manipulation of vortices in a BEC is continued, building on previous successful methods that use moving laser beams to generate and manipulate vortices so that specific arrangements of vortices or types of fluid flow can be created and used on-demand in quantum fluid dynamics experiments. Finally, newly observed methods of vortex nucleation are examined in order to more fully round out an understanding of how vortices and turbulent fluid flows can be generated in BECs. By exploring the dynamics of BEC vortices, this work advances a broader understanding of quantum many-body phenomena in systems with vastly different microscopic properties, such as superfluids, superconductors, and the cores of neutron stars. The project relies on and promotes the scientific education and technical training of students, keys to maintaining national scientific strength and societal breadth and creativity.