Excitations, Rotational Dynamics, and Rotational Sensing in 2-Species Bose-Einstein Condensates

我们的研究涉及超冷原子系统中量子多体动力学的理论和实验研究，以开发下一代旋转传感器的观点，以及开发工具并提高我们对远离平衡的相互作用多体系统的一般理解。中心思想是基于使用具有玻色子自旋统计的超冷原子，与之相反，例如，电子绕原子核运行，其中两个具有相同自旋的电子不能完全占据相同的能级或轨道（费米子自旋统计）。这意味着在足够低的温度下，由这种玻色子原子组成的稀原子气体会经历一种特殊的相变。相变是一种突然的、质的状态变化，就像普通气体随着温度的降低而凝结成液态一样。非常稀的低温玻色子原子所达到的物质状态被称为玻色-爱因斯坦凝聚体。这可以看作是激光的原子/物质等效物；一种连贯的、强烈的原子源，对测量科学或计量学（在光的情况下，受光可见的最小波长的限制，并由传统光学控制）有相应的好处。不幸的是，原子间的相互作用通常是有问题的，而且往往会抵消相干原子源的优点。我们将以一个建议（一位研究者建议）为基础，在这个建议中，由于巧妙地选择了实验几何结构，与原子-原子相互作用有关的问题似乎在很大程度上被避免了。在研究这个系统以及一些密切相关的问题的过程中，我们将加深我们对非平衡动力学的理解（例如，由于在任何功能旋转传感器中避免诸如流动不稳定之类的事情至关重要），并开发广泛适用的理论工具来解释复杂的多体效应的影响和产生。因此，我们的研究属于EPSRC物理学大挑战“涌现和远离平衡的物理学”（动机是“戏剧性的集体行为可能在大型复杂系统中意外出现”和“这项基础工作将由涌现状态可能为未来技术提供基础的永远存在的可能性驱动”）和“新量子技术的量子物理学”（动机是“下一代量子技术将依赖于量子物理学”）我们对相干和纠缠的理解和利用”和“成功需要对量子物理学有更深入的理解，需要对使能工具和技术进行广泛的开发”)。超冷原子是研究远离平衡的动力学的理想配置，因为它们的实验配置具有非常高的灵活性（通过适当的磁场、激光和微波场组合，可以改变实验几何形状、相互作用的强度，甚至相互作用是吸引还是排斥），而且原子、分子和光学（AMO）物理系统在精确测量方面具有最高的记录。最引人注目的是原子钟，例如，它支撑着全球定位系统（GPS）的功能。

Our research involves the theoretical and experimental investigation of quantum many-body dynamics in systems of ultra-cold atoms, with the view of developing next-generation rotational sensors, and developing tools for and improving our general understanding of interacting many-body systems far from equilibrium. The central idea is based on using ultra-cold atoms with bosonic spin statistics, in contrast to e.g., electrons orbiting an atomic nucleus, where two electrons with the same spin cannot occupy exactly the same energy level or orbital (fermionic spin statistics). This means that at sufficiently low temperatures a dilute atomic gas composed of such bosonic atoms undergoes a particular kind of phase transition. A phase transition is a sudden, qualitative change of state, like and ordinary gas condensing to a liquid state as the temperature is lowered. The state of matter reached in the case of very dilute, low temperature bosonic atoms is called a Bose-Einstein condensate. This can be seen as the atomic/matter equivalent of a laser; a coherent, intense source of atoms, with consequent advantages to measurement science or metrology (which in the case of light are limited by the minimum wavelength for the light to be visible and controlled by conventional optics). Atom-atom interactions are, unfortunately, typically problematical, and tend to counteract the advantages of a coherent atomic source. We will build upon a proposal (suggested one of the investigators) where the issues associated with atom-atom interactions appear to be largely avoided due to an astutely chosen experimental geometry. In the process of investigating this proposed system as well as a number of closely related issues, we will deepen our understanding of nonequilibrium dynamics (due, for example, to the crucial importance of avoiding such things as flow instabilities in any functioning rotational senser), and develop broadly applicable theoretical tools accounting for the influence and production of complicated many-body effects. As such our research falls within the EPSRC Physics Grand Challenges "Emergence and Physics Far From Equilibrium" (motivated by the fact that "dramatic collective behaviour can emerge unexpectedly in large complicated systems" and "This fundamental work will be driven by the ever-present possibility that emergent states may provide the foundations for the technologies of the future") and "Quantum Physics for New Quantum Technologies" (motivated by "Next generation quantum technologies will rely on our understanding and exploitation of coherence and entanglement" and "Success requires a deeper understanding of quantum physics and a broad ranging development of the enabling tools and technologies").Ultracold atoms are an ideal configuration in which to investigate dynamics far from equilibrium, due to a very high degree of flexibility in their experimental configurations (varying the experimental geometry, strength of interaction, and even whether the interactions are attractive or repulsive, by appropriate combinations of magnetic, laser and microwave fields), and atomic, molecular and optical (AMO) physics systems have a superlative record in terms of precision measurement, most notably in the form of atomic clocks, which, for example, underpin the functioning of the global positioning system (GPS).