INTERACTIVE DYNAMICS OF MANY-BODY QUANTUM SYSTEMS

多体量子系统的交互动力学

• 批准号: EP/X030881/1
• 负责人: Fabian Essler
• 金额: $ 172.58万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX030881%2F1
• 关键词: INTERACTIVE; DYNAMICS; MANY; BODY; QUANTUM

In our everyday life we rarely think about the effects of quantum mechanics, and yet they are constantly around us, determining the properties of every material object in our world. The laws of quantum physics define every property of matter, from the behaviour of individual atoms, to how the atoms bind together to form materials, to the characteristics of these resultant materials. They also determine if and how systems of many interacting particles establish an equilibrium or steady state governed by a handful of statistical laws.Physicists are now able to engineer large, tunable collections of interacting quantum particles, both in quantum computing devices and in ultracold atomic gases and solid-state materials. Often, such systems cannot be described by standard techniques that focus on quantum states that have simple structures. In many cases, the routes by which such systems come to equilibrium involve subtle and surprising features of quantum mechanics, necessitating entirely new ways of thinking, or require substantial extensions of older approaches such as hydrodynamics. Another striking new idea that has emerged recently is that quantum mechanical coherence can be preserved even when many-body systems are far from their lowest-energy state. The word "coherence" here implies that many microscopic objects are acting together in concert. Such behaviour, when it occurs, allows for the effects of quantum physics to be greatly enhanced, but it is usually washed out as systems achieve equilibrium, which can often be described well using classical physics. Finding routes to evade this equilibrium allows for new and unusual physical phenomena with significant potential utility for quantum technology.Yet a third set of new concepts is motivated by the capabilities of the present-day "noisy, intermediate-scale quantum" (NISQ) devices. In contrast to conventional platforms, these offer the possibility of punctuating the time evolution of a many-body system by measurements, and using the results to shape future evolution - a new form of "quantum interactive dynamics", where the scientist is an active participant rather than a passive spectator. Understanding the new states of matter enabled in this setting and the protocols needed to implement them on NISQ processors is an exciting new frontier.We have organised our research into three themes:(1) What are the mechanisms by which quantum systems approach an equilibrium state?We will develop a better understanding of universal aspects of the equilibrium state in quantum many-body systems. We will also seek to understand certain experimental systems, such as cold atomic gases or solid-state materials, that can be studied using hydrodynamic principles and their generalizations.(2) How can quantum many-body systems evade thermalization to access novel non-equilibrium regimes?We will seek to understand how frozen-in randomness and special symmetries can arrest the approach to equilibrium and allow quantum coherence to persist even in highly excited states.(3) What new possibilities are enabled by "quantum interactive dynamics"?We will clarify how the evolution of quantum systems towards or away from equilibrium can be shaped by measurement and feedback.The answers to these questions are likely to be central in harnessing the full power of quantum mechanics to accomplish complex tasks. Understanding the far-from-equilibrium and interactive dynamics of quantum many-particle systems is likely to play a similar role in the development of future quantum computing devices as the quantum theory of solids did in the technological revolutions of the past century. Thus, while our research is mainly academic in nature, we hope that our discoveries will enable technologies needed to address the challenges of the next century.

在我们的日常生活中，我们很少考虑量子力学的影响，但它们总是围绕着我们，决定着我们世界中每一个物质对象的属性。量子物理学定律定义了物质的每一种性质，从单个原子的行为，到原子如何结合在一起形成材料，再到这些合成材料的特性。它们还决定了许多相互作用粒子的系统是否以及如何建立一个由少数统计定律支配的平衡或稳定状态。物理学家现在能够在量子计算设备和超冷原子气体和固态材料中设计大量可调的相互作用量子粒子集合。通常，这样的系统不能用专注于具有简单结构的量子态的标准技术来描述。在许多情况下，这些系统达到平衡的途径涉及量子力学的微妙和令人惊讶的特征，需要全新的思维方式，或者需要对流体力学等旧方法进行实质性的扩展。最近出现的另一个引人注目的新想法是，即使多体系统远离其最低能量状态，量子力学相干性也可以保持。这里的“一致性”一词意味着许多微观物体在一致地共同作用。这种行为，当它发生时，允许量子物理学的效果被大大增强，但它通常会随着系统达到平衡而被淘汰，这通常可以用经典物理学很好地描述。找到避开这种平衡的途径，就能产生对量子技术具有重大潜在效用的新的、不寻常的物理现象，而第三组新概念则是由当今“噪声、中间尺度量子”（NISQ）设备的能力所激发的。与传统平台相比，这些平台提供了通过测量来打断多体系统的时间演化的可能性，并使用结果来塑造未来的演化-一种新形式的“量子交互动力学”，其中科学家是积极的参与者而不是被动的旁观者。理解在这种情况下启用的新物质状态以及在NISQ处理器上实现它们所需的协议是一个令人兴奋的新前沿。我们将我们的研究分为三个主题：（1）量子系统接近平衡态的机制是什么？我们将更好地理解量子多体系统中平衡态的普遍性。我们还将试图了解某些实验系统，如冷原子气体或固态材料，可以使用流体动力学原理及其推广进行研究。(2)量子多体系统如何避免热化以进入新的非平衡态？我们将试图理解冻结的随机性和特殊对称性如何阻止平衡的接近，并允许量子相干即使在高度激发态下也能持续存在。(3)“量子相互作用动力学”带来了哪些新的可能性？我们将阐明如何通过测量和反馈来塑造量子系统朝向或远离平衡的演化。这些问题的答案可能是利用量子力学的全部力量来完成复杂任务的核心。理解量子多粒子系统的远离平衡态和相互作用动力学，很可能在未来量子计算设备的发展中发挥类似的作用，就像固体的量子理论在过去世纪的技术革命中所发挥的作用一样。因此，虽然我们的研究主要是学术性质的，但我们希望我们的发现将使技术能够应对下一个世纪的挑战。