Quantum Coherent Applications of Superfluid 3He

非技术描述：在物理学扮演重要角色的今天，有两个重要的挑战。首先是开发能够处理数字信息时代的复杂和浩瀚的新一代计算机。这些假定的量子计算机利用了物质的量子状态，这些状态包含的信息可以在足够低的温度下存储和操作，以至于热涨落和杂质都不会破坏它们的相干性。这类量子态的一种重要形式是一种健壮的超导电性，它不具有镜像对称性，被称为手性，类似于扭曲的DNA链。具有这种性质的量子材料的范例是超流3He。对3He量子相干项目的研究验证了一个基本预测，即反常热霍尔可以提供对任何超导体手性的明确识别，而超导体是量子计算的候选材料。还有第二个挑战。我们的宇宙似乎丢失了70%的质量，即所谓的暗物质。除了暗物质对星系中恒星分布的引力影响外，没有观测到暗物质。它不存在于所有其他观察之中，这是一个存在的问题。人们已经发起了许多尝试，以开发高分辨率的传感工具，以识别这种丢失的质量，因为它淹没了我们的环境。一种可能的探测器是基于超流3He中I核自旋进动态的高相干。其已知的连贯性使其成为这一目的的一个非常有吸引力的选择；但连贯性的局限性尚未得到充分探索。3He自旋进动用于质量传感的第二个独特优点是它的可调性，允许在大范围的暗质量范围内进行连续的现场测量。技术描述：超流氦-3是一个已知的拓扑量子凝聚系统，是理解复杂量子材料，特别是奇宇称手性超导体的模型；是新兴量子信息科学领域的研究人员感兴趣的课题。超流3He的量子相干应用项目是一个改善和展示包括超导量子材料在内的手性量子系统之间的量子相干的平台。此外，这些材料为基于量子传感的仪器发展提供了机会。其中一个重要的应用解决了存在的问题，即如何确定暗物质的性质。对于所选择的超流3He系统，量子自由度是它的核自旋和轨道角动量在宏观尺度上连贯地表现出来的。超流~3He吸附在非常高的孔隙率(98%)中，均匀各向异性的二氧化硅气凝胶控制着自旋和轨道角动量量子化轴。利用核磁共振，可以明确地确定这些轴的方向。最近的理论预测，在均匀各向异性二氧化硅气凝胶中观察到的超流体中的非零热霍尔效应定义了垂直于热梯度的手性轴。这一理论的证实提供了一种独特的工具，即横向热导的测量，可以用来确定手性。这一应用扩展到与量子信息科学相关的超导材料。量子传感是该项目的第二个应用。超流3He的长寿命量子自旋相干态为探测暗物质提供了一种很有前途的探测器。重要的是，在这种情况下，高传感灵敏度与对假定的暗质量进行连续调谐的优势相结合，从而至少建立了对银河系轴子产生的限制，这是现代物理学中存在的一个问题。这个项目的关键是它与超流3He和暗物质领域的理论物理学家的合作伙伴关系，以及西北大学的低温和核磁共振光谱专业知识。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Description:There are two important challenges today where physics plays an essential role. The first is to develop a new generation of computers that can handle the complexity and vastness of the digital information age. These putative quantum computers take advantage of quantum states of matter which contain information that can be stored and manipulated at sufficiently low temperature that neither thermal fluctuations nor impurities destroy their coherence. One important class of such quantum states is a robust form of superconductivity which does not have mirror symmetry and is called chirality, analogous to twisted strands of DNA. The paradigm quantum material having this property is superfluid 3He. Investigation in this project of quantum coherence in 3He tests a fundamental prediction that the anomalous thermal Hall can provide an unambiguous identification of chirality in any superconductor that is a candidate material for quantum computation. There is a second challenge. Our universe appears to be missing 70% of its mass, so-called dark matter. Dark matter is unobserved except for its gravitational impact on star distributions in galaxies. Its absence from all other observation is an existential problem. Many attempts have been launched to develop high resolution sensing tools to identify this missing mass as it floods throughout our environment. A possible detector is based on high coherence of i nuclear spin precession states in superfluid 3He. Its known coherence makes it a very attractive choice for this purpose; yet the limits of coherence have not yet been fully explored. A second unique benefit of 3He spin precession for mass sensing, is its tunability allowing continuous measurements in situ to be made over a wide range of dark mass.Technical Description:Superfluid helium-three is a known topological quantum condensed system, a model for understanding complex quantum materials and in particular, odd-parity chiral superconductors; a subject of interest to researchers in the burgeoning field of quantum information science. The project Quantum Coherent Applications of Superfluid 3He, is a platform to improve and demonstrate quantum coherence among chiral quantum systems including superconducting quantum materials. Additionally, these materials provide an opportunity for instrumentation development based on quantum sensing. One such important application addresses the existential problem, how to determine the nature of dark matter. For superfluid 3He, the paradigm system of choice, the quantum degrees of freedom are its nuclear spin and orbital angular momentum coherently manifest on a macroscopic scale. Superfluid 3He imbibed into very high porosity (98%) uniformly anisotropic silica aerogel controls both the spin and orbital angular momentum quantization axes. Using nuclear magnetic resonance, the directions of these axes can be unambiguously determined. Recent theory predicts that observation of a non-zero thermal Hall effect in the superfluid in uniformly anisotropic silica aerogel defines the chiral axis perpendicular to a thermal gradient. Confirmation of this theory provides a unique tool, measurement of the transverse thermal conductance, that can be used to determine chirality. The application extends to superconducting materials relevant to quantum information science. Quantum sensing is a second application in this project. The long-lived, quantum-spin coherent state of superfluid 3He provides a promising detector for light dark matter. Importantly, in this case high sensing sensitivity is combined with the advantage of continuous tuning for the putative dark mass, thereby at the very least establishing limits on galactic axion production, an existential problem in modern physics. Key to this project is its partnership with theoretical physicists in both the fields of superfluid 3He and dark matter, together with cryogenic and nuclear magnetic resonance spectroscopy expertise at Northwestern.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.