Quantum Enhanced Superfluid Technologies for Dark Matter and Cosmology

QUEST-DMC计划试图回答现代物理学面临的一些最基本的问题：早期宇宙的物理学是什么？暗物质的本质是什么？物质-反物质不对称的起源是什么？我们将重点研究早期宇宙宇宙学的两个核心组成部分，它们可能从根本上联系在一起：暗物质的身份和性质以及相变的物理。通过将宏观量子系统--超流氦-3(3He)与最先进的量子技术相结合，我们将开创一项具有前所未有的发现潜力的新的暗物质搜索实验。同时，我们将利用超流3He的独特性质作为早期宇宙相变的量子模拟器。暗物质在宇宙的演化中扮演着至关重要的角色，例如，它在早期宇宙结构的形成中发挥了核心作用，今天在阻止星系分裂方面发挥了关键作用。到目前为止，暗物质研究和搜索的重点一直是弱相互作用大质量粒子(WIMP)，其预测的质量范围大致在质子的10-1000倍之间。到目前为止，对这一暗物质候选者的直接、间接和对撞机搜索一直很广泛，但最终都没有成功。有一个扩大研究范围的强烈动机。宇宙只由没有反物质的物质组成这一事实需要解释，因为假设物质和反物质在大爆炸中产生的数量相等是合理的。这意味着在宇宙演化过程中，发生了一个动态地产生物质和反物质之间的不对称性的过程。将暗物质的动力学与物质/反物质不对称性的产生联系起来的模型自然预测出暗物质的质量尺度接近质子的质量，约为1GeV/c2，这意味着标准WIMP的另一个目标质量范围。该项目将创建和操作一个探测器，使用具有世界领先灵敏度的超流氦-3作为目标，直接搜索亚GeV质量的暗物质。这个项目的第二个主要组成部分是对相变物理学的详细研究。相变是在极端条件下，例如早期宇宙或中子星内部的极端条件下，粒子物理标准模型对称破缺范式的关键预测。一阶相变产生了一个特有的引力波信号，并形成了引力波搜索的主要动机。根据我们目前对相变机制的理解，即成核理论，在标准模型中没有预测到引力波。如果探测到引力波，并且它们的起源可以与早期宇宙中的相变联系在一起，那么这将是粒子物理标准模型之外的物理学的证据，对我们对基础物理的理解有很大影响。至关重要的是，测试相变的物理学，以便充分利用欧洲航天局批准的定于2034年发射的LISA任务等实验。这个项目将利用超流3He中不同量子真空之间的相变来实现这一点，在受控条件下，作为量子模拟。这个项目集合了宇宙学、超低温和量子技术的前沿。这两个实验都利用了超流氦-3的独特性质，它被冷却到绝对零度以上100微开尔文。它将依赖于一系列最先进的超导量子传感器，以及纳米级结构，如纳米束谐振器，以及结构化纳米尺度限制。从长远来看，量子技术的未来发展将在亚GeV暗物质搜索的灵敏度和范围方面产生进一步的改进。

The QUEST-DMC programme seeks to answer some of the most fundamental questions facing modern physics: What is the physics of the early universe? What is the nature of dark matter? What is the origin of the matter-antimatter asymmetry? We will focus on the investigation of two core building blocks of early universe cosmology, which may be fundamentally linked; the identity and nature of dark matter and the physics of phase transitions. By combining a macroscopic quantum system, superfluid helium-3 (3He), with state-of-the-art quantum technologies we will pioneer a new dark matter search experiment with unprecedented discovery potential. In parallel we will use the unique properties of superfluid 3He as a quantum simulator of phase transitions in the early universe.Dark Matter plays a vital role in the evolution of the universe, for example, it played a central role in the formation of structure in early universe and today plays a key role in stopping galaxies flying apart. The focus of dark matter studies and searches to date has been on Weakly Interacting Massive Particles (WIMPs) whose predicted mass range is broadly speaking between 10-1000 times that of the proton. The direct, indirect and collider searches for this dark matter candidate to date have been extensive but ultimately unsuccessful. There is a strong motivation to widen the search.The fact that the universe only consists of matter with no anti-matter requires explanation, since it is reasonable to assume that matter and anti-matter were produced in equal quantities in the Big Bang. This implies that during the evolution of the universe a process took place that dynamically generated the asymmetry between matter and anti-matter. Models linking the dynamics of dark matter with the generation of the matter/anti-matter asymmetry naturally predict a mass scale of dark matter that is close to the mass of the proton, of order 1 GeV/c2, suggesting an alternative target mass range to the standard WIMP. This project will create and operate a detector for the direct search of dark matter with sub-GeV masses using superfluid helium-3 as a target with world-leading sensitivity. The second major component of this project is a detailed investigation of the physics of phase transitions. Phase transitions are a key prediction of the symmetry-breaking paradigm of the Standard Model of particle physics in extreme conditions, such as those of the early universe or inside neutron stars. A first-order phase transition produces a characteristic gravitational wave signature and forms a leading motivation for gravitational wave searches. According to our current understanding of the mechanism of phase transitions, called nucleation theory, no gravitational waves are predicted in Standard Model. If gravitational waves are detected and their origins can be linked to a phase transition in the early universe then this would be evidence of Physics beyond the Standard Model of particle physics, with high impact on our understanding of fundamental physics. It is critical that the physics of phase transitions is tested so that experiments such as the approved European Space Agency mission LISA due for launch in 2034 are fully exploited. This project will do this using phase transitions between different quantum vacua in superfluid 3He, under controlled conditions, as a quantum analogue. This programme brings together the frontiers of cosmology, ultralow temperatures and quantum technology.Both experiments exploit the unique properties of superfluid helium-3, cooled to 100 microkelvin above absolute zero. It will rely on a range of state-of-the-art superconducting quantum sensors, and nanofabricated structures such as nanobeam resonators, and structured nanoscale confinement. Future developments in quantum technologies will generate further improvements in sensitivity and range of the sub-GeV dark matter search in the longer term.