Silencing the noise in quantum circuits by a Quantum fluid Bath - SQuBa

通过量子流体浴消除量子电路中的噪声 - SQuBa

• 批准号: EP/Y022637/1
• 负责人: John Saunders
• 金额: $ 171.95万
• 依托单位: Royal Holloway University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FY022637%2F1
• 关键词: Silencing; noise; quantum; circuits; Quantum

Quantum computers will have a transformative impact by solving hitherto intractable problems in science and enable multiple innovations across society and the economy, derived from the exponential increase in computing power. Ultimately performance and ease of implementation are primarily limited by the quality of the basic building block; the qubit. Furthermore quantum sensors will lead to a new era of discovery in fundamental science, due to step changes in detector sensitivity. Superconducting qubits provide a scalable technology, strongly favoured by industry. However, quantum states are very fragile, making the qubit highly sensitive to its environment. This includes spurious sources of energy (heat) and the quantum bath of material defects. These notoriously ubiquitous defects can broadly be categorised as two types: surface spins and two-level system defects (TLS). Both are a source of noise and decoherence in circuits and constitute a significant roadblock to technological applications. The ability to both adequately cool circuits and eliminate the deleterious effects of defects, the nature of which remains poorly understood after decades of study, are the two major obstacles towards improved coherence and large-scale quantum computing. The central research hypothesis behind this proposal is that immersion of the quantum circuit in a quantum fluid bath (for example liquid helium-three) presents an elegant, scalable, solution to both these problems. It is motivated by striking results we obtained on a simple quantum circuit (superconducting resonator) immersed in liquid helium-three.The overarching objective of this project is a systematic investigation of the suppression of decoherence in superconducting quantum circuits (qubits and resonators) cooled through immersion in a quantum fluid bath, and to achieve a fundamental understanding of its origin via the interaction of the circuit and its environment to the quantum fluids. This will be combined with strain and electric field tuning to pin-point TLS, enabling new circuit designs to optimally draw upon immersion cooling for enhanced coherence. The coupling between qubit and the quantum fluid bath provides a new pathway to mitigate decoherence. In contrast over the last decades, mitigation of decoherence by TLS through device design has yielded most of the improvements in coherence times. The materials science of eliminating TLS is a major future challenge, now receiving much attention, here with a completely new tool at our disposal. Thus far the relative stagnation in coherence times has driven an approach to quantum computing with error correction in which many physical qubits are required to realise a single logical qubit. Furthermore, we aim to identify the optimal quantum bath conditions at which to operate circuits for enhanced performance. Through engagement with the theoretical physics community, we aim to develop testable hypotheses for the quantum fluid-quantum circuit interaction, to help guide the experimental programme towards most efficiently achieving the main objective: a step-change in qubit performance. We aim to significantly advance the understanding of properties of amorphous dielectrics in quantum circuits (nature of TLS and their interactions), in particular on surfaces. Finally, we will investigate the feasibility of quantum fluid immersion scalability for quantum computers, with a view to accelerate the impact of our fundamental research.In this work quantum circuits meet quantum fluids, and much fundamental work remains to unpick the underlying mechanisms at play. The promise of performance optimisation lies in the tunability of the quantum fluid and its interface with the quantum circuit. We therefore believe that the success of this project will trigger a step-change in the progress towards fault-tolerant quantum computing.

量子计算机将通过解决迄今为止棘手的科学问题来产生变革性的影响，并通过计算能力的指数级增长实现整个社会和经济的多项创新。最终，性能和易于实施主要受到基本构建块质量的限制；量子位。此外，由于探测器灵敏度的阶跃变化，量子传感器将引领基础科学发现的新时代。超导量子位提供了一种可扩展的技术，受到业界的大力青睐。然而，量子态非常脆弱，使得量子位对其环境高度敏感。这包括虚假能源（热）和材料缺陷的量子浴。这些众所周知的普遍存在的缺陷大致可分为两种类型：表面自旋和两级系统缺陷（TLS）。两者都是电路中的噪声和退相干源，并构成技术应用的重大障碍。充分冷却电路和消除缺陷有害影响的能力是提高相干性和大规模量子计算的两个主要障碍，经过数十年的研究，缺陷的本质仍然知之甚少。该提案背后的中心研究假设是将量子电路浸入量子流体浴（例如液氦三）中，为这两个问题提供了一种优雅的、可扩展的解决方案。它的动机是我们在浸入液氦三的简单量子电路（超导谐振器）上获得的惊人结果。该项目的总体目标是系统研究超导量子电路（量子位和谐振器）中退相干的抑制沉浸在量子流体浴中，并通过电路及其环境与量子流体的相互作用来基本了解其起源。这将与应变和电场调谐相结合以精确定位 TLS，使新的电路设计能够最佳地利用浸没式冷却来增强相干性。量子位和量子流体浴之间的耦合提供了减轻退相干的新途径。相比之下，在过去的几十年里，通过设备设计通过 TLS 缓解退相干已经在相干时间方面取得了大部分改进。消除 TLS 的材料科学是未来的一项重大挑战，现在受到了广泛关注，这里有一个全新的工具可供我们使用。迄今为止，相干时间的相对停滞推动了一种具有纠错功能的量子计算方法，其中需要许多物理量子位来实现单个逻辑量子位。此外，我们的目标是确定运行电路以增强性能的最佳量子浴条件。通过与理论物理界的合作，我们的目标是为量子流体-量子电路相互作用开发可测试的假设，以帮助指导实验计划最有效地实现主要目标：量子位性能的阶跃变化。我们的目标是显着增进对量子电路中非晶电介质特性（TLS 的性质及其相互作用）的理解，特别是在表面上。最后，我们将研究量子计算机的量子流体浸入式可扩展性的可行性，以期加速我们基础研究的影响。在这项工作中，量子电路遇到了量子流体，还有许多基础工作需要解开起作用的潜在机制。性能优化的希望在于量子流体及其与量子电路的接口的可调谐性。因此，我们相信该项目的成功将引发容错量子计算进展的阶跃变化。