Pushing the boundaries of superfluid vacuum and coherence

宏观量子系统，如超流体、超导体和原子气体凝聚体，将量子物理学带到了肉眼可观察的尺度。这些量子相干现象起源于实验室，但现在要么已经用于商业应用（例如超导体），要么正在积极开发技术应用（例如玻色凝聚）。与此同时，我们对这些系统的知识不断扩展，揭示了前所未有的现象：一个很好的例子是最近发现的时间晶体，它弯曲了永动机的绝对不可能性。拟议的研究计划将探索超流体3 He中宏观量子秩序的边缘。超流3 He是一个宏观量子系统，具有极其丰富的现象学，触及高能物理和宇宙学等看似遥远的领域。最著名的例子是希格斯机制，它最初是在超导体（非流体）系统中发现的，后来成为粒子物理学标准模型的一部分。另一个例子是Kibble-Zurek机制，最初是一种宇宙学推测，在超流体3 He中发现，现在成为现代实验室物理学的基石。从力学角度理解低温超流3 He的正确方法是考虑真空，在真空中，棒可以四处移动，就好像超流一开始就不存在一样。只有当探测超过真空的固有阈值，例如由库珀对尺寸设定的最小尺寸或由超流能隙设定的最大速度，真空的量子性质才会被揭示。这意味着真空不再是背景，并开始与探针相互作用。例如，一个足够小的探针将揭示真空的内在结构，这是隐藏在大探针。一个意想不到的内在结构的推论是，超流体的表面形成了一个几乎与三维体相分离的二维系统：将一根棒移近表面，释放的任何能量都会粘在表面上。超流体的磁性在很大程度上取决于从大体积真空中出现的磁性粒子的动力学。这些粒子可以形成时间晶体，一种永久重复运动的物质动态相。其他“时间相”，如无序的时间液体，可以用类似的方法创造，并通过利用平衡物理工具箱来探索动态系统来解释。这个奖学金将探索量子真空机械和磁性：1。我将领导探索表面束缚费米子，在几百纳米厚的超流3 He表面层中进行一系列输运实验。在实践中，这意味着在一个点加热表面层，并通过测量表面上另一个点的温度来观察热量如何沿着表面流动。为该项目委托的技术还将允许通过在超流体中移动一个微小的棒来揭示超流体真空的内在结构，其中与真空的相互作用在小于库珀对半径的尺度上发生显着变化。1.我的团队将通过熔化一个量子时间晶体来创造一种新的玻色子相物质，这种物质会自发地变得不相干--一种时间液体。通过增加颗粒密度来启动熔化过程。绘制超流真空中“时间相”的相图将巩固这一新的研究领域。该项目得到了主办机构和国际上领先的技术，实验和理论合作者的支持。该奖学金提供的发现将引领新的研究领域，其学术和技术影响涵盖从束缚费米子的二维物理到基于磁振子的室温量子器件。

Macroscopic quantum systems such as superfluids, superconductors, and atomic gas condensates bring quantum physics to scales observable by the naked eye. These quantum-coherent phenomena originated in the laboratory but are now either already used for commercial applications (for example superconductors) or being actively developed with technological applications in mind (for example Bose condensates). At the same time the edges of our knowledge about these systems keep being extended, revealing unprecedented phenomena: a good example is the recent discovery of time crystals that bend the categorical impossibility of perpetual motion machines. The proposed research programme will explore the edges of macroscopic quantum order in superfluid 3He. Superfluid 3He is a macroscopic quantum system with extremely rich phenomenology, touching seemingly distant fields such as high-energy physics and cosmology. The most famous example is the Higgs mechanism, which was originally discovered in a superconductor (-fluid) system and later become a part of the Standard Model of particle physics. Another example is the Kibble-Zurek mechanism, originally a cosmological speculation, which was discovered in superfluid 3He and now forms a cornerstone of modern laboratory physics. The right way to understand low-temperature superfluid 3He from a mechanical perspective is to think about a vacuum where a rod can be moved around as if the superfluid is not there in the first place. Only if the probing exceeds an intrinsic threshold of the vacuum, such as a minimum size set by the Cooper pair size or a maximum velocity set by the superfluid energy gap, will the quantum nature of the vacuum be revealed. This means that the vacuum ceases to be a background and starts interacting with the probe. For example, a probe that is small enough will reveal the intrinsic structure of the vacuum which is hidden from large probes. An unexpected corollary of the intrinsic structure is that the surfaces of the superfluid form a two-dimensional system nearly detached from the three-dimensional bulk: move a rod near the surface and any energy released will be stuck to the surface. The magnetic properties of the superfluid are largely determined by the dynamics of magnetic particles emerging from the bulk vacuum. These particles can form a time crystal, a dynamic phase of matter in permanent repeating motion. Other "time phases" such as disordered time liquids can be created with a similar approach and explained by harnessing the toolbox of equilibrium physics to explore dynamic systems. This fellowship will explore the quantum vacuum mechanically and magnetically: 1. I will lead the exploration of the surface-bound fermions by carrying out a series of transport experiments in the few hundred nanometre thick surface layer of superfluid 3He. In practice this means heating the surface layer at one point and observing how the heat flows along the surface by measuring temperature at another point on the surface. The technology commissioned for this project will also allow revealing the superfluid vacuum's intrinsic structure by moving a tiny rod in the bulk of the superfluid where the interaction with the vacuum dramatically changes at scales smaller than Cooper pair radius. 1. My team will create a new bosonic phase of matter which spontaneously becomes incoherent - a time liquid - by melting a quantum time crystal. The melting process is initiated by increasing the particle density. Mapping the phase diagram of the "time phases" in the superfluid vacuum will cement this new field of study. This project is backed by leading technical, experimental and theoretical collaborators in the Host Institution and internationally. Discoveries delivered by this fellowship will lead new fields of research with academic and technological implications spanning from two-dimensional physics of bound fermions to magnon-based room temperature quantum devices.