CAREER: Spin-Magnon based Hybrid Quantum Devices

量子系统显示出迷人的反直觉叠加特性，即同时处于多个状态的能力，以及纠缠，即发展远距离多体关联的能力。这些特性为构建量子技术提供了机会，例如传感、通信和信息处理，这些能力在经典领域是无法实现的。近年来，在这一前景的推动下，在设计和控制各种单个量子系统方面取得了巨大进展。其中，绝缘材料中的自旋缺陷，即微观自旋量子比特（qubit）尤其有前景。自旋通过磁偶极矩与环境相互作用：这一事实被用于磁场的量子传感，具有前所未有的空间分辨率和灵敏度。另一方面，承载自旋量子比特的典型材料中的环境产生弱磁场，因此自旋量子比特中编码的量子态可以存活很长时间，这一事实使自旋量子比特成为量子记忆和信息处理的有吸引力的候选者。下一个前沿领域旨在扩展基于自旋的量子硬件的功能，其中包括开发自旋量子比特的能力：(i)在磁场之外感知信号，以开发新型量子传感器，以及（ii）在保留单个寻址能力的同时，在少数近端放置的自旋量子比特之外可控地相互作用，以进行量子信息处理。然而，由于缺乏一种可以控制和强耦合自旋量子位以及广泛的外部信号的介质，这被证明是具有挑战性的。在这个项目中，主要研究者将利用磁振子（即磁铁中的集体激发）作为一种全新的介质来解决这一挑战。在与研究紧密结合的情况下，首席研究员还将开发一门量子工程课程，用于培训本科生、研究生和行业专业人员，以增强美国的量子智能劳动力。提出的研究旨在通过将理论与原理证明实验相结合来揭示新型的磁振子自旋-量子比特混合器件。特别是，首席研究员将追求以下设备类型。(a)传感型器件——这些器件的中心目标是增强自旋量子位对信号（如电场、温度）的传感能力。这将通过使用磁振子作为外部信号到磁信号的换能器来实现。(b)信息处理类型设备——这些设备的中心目标将是解决为自旋量子位设计可扩展信息处理架构的挑战，其中量子位可以在不同长度尺度上相干耦合，同时保持本地寻址能力。为此，理论方案和原理验证实验将展示相干耦合经典信号，通过设计的磁振子共振模式的电泵局部自旋量子位。此外，通过设计磁共振模式，将开发自旋量子位元和磁振子在量子态之间传递信息的方案。为了实现上述目标，首席研究员将把光子/声子-量子比特杂化（即腔和电路量子电动力学）的成熟设计原则转化为提出的磁non-spin-qubit系统。除了这些相似之处，磁振子还具有独特的能力，例如凝聚成类超流体模式，以及类孤子模式，以及固有的手性传播。因此，所提出的研究有望揭示磁系统独特的全新器件概念，例如单向手性自旋-自旋耦合。从理论上探索这些装置概念也将构成本提案的一个组成部分。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum systems show fascinating counterintuitive properties of superposition, i.e. the ability to be simultaneously in multiple states, and entanglement, i.e. the ability to develop long-distance many-body correlations. These properties present opportunities to build quantum technology, such as sensing, communication and information processing, with capabilities not achievable in the classical domain. In recent years motivated by this promise, tremendous progress has been achieved to engineer and control a variety of individual quantum systems. Among these, spin defects in insulating materials, i.e. microscopic spin quantum bits (qubits) are particularly promising. Spin interacts with the environment through their magnetic dipole moments: a fact utilized for quantum sensing of magnetic fields with unprecedented spatial resolution and sensitivity. On the other hand, the environment in typical materials hosting spin qubits produces weak magnetic fields, consequently the quantum states encoded in the spin qubits survive for long times, a fact that makes spin qubits attractive candidates for quantum memory and information processing. The next frontier aims at scaling the functionality of spin-based quantum hardware, which includes developing the ability of spin qubits to:(i) sense signals beyond magnetic fields for developing novel quantum sensors, and (ii) controllably interact beyond few proximally-placed spin qubits while retaining individual addressability, for quantum information processing. This has however proved challenging due to the lack of a mediator which can controllably and strongly couple to spin qubits as well as to a wide range of external signals. In this project, the principle investigator will exploit magnons (i.e. the collective excitations in magnets), as a fundamentally novel mediator to address this challenge. In tight integration with research, the principal investigator will also develop a quantum engineering course for training undergraduate, graduate and industry professionals for enhancing the United States quantum-smart workforce. The proposed research aims at unraveling novel magnon spin-qubit hybrid devices by integrating theory with proof-of-principle experiments. In particular, the principal investigator will pursue the following device types. (a) Sensing-type devices- the central aim of these devices will be to enhance sensing capability of spin qubits for signals, such as, electric fields, temperature. This will be achieved by using magnons as transducers of external signals to a magnetic signal. (b) Information processing-type devices- the central aim of these devices will be to address the challenge of designing a scalable information-processing architecture for spin qubits, where qubits can be coherently coupled across varied length scales while maintaining local addressability. For this purpose, theoretical schemes and proof-of-principle experiments will be demonstrated for coherently coupling classical signals to spin qubits locally via electrical pumping of designed magnon resonance modes. In addition, schemes will be developed for transferring information between spin-qubits and magnons in the quantum regime by designing the magnetic resonance modes. To achieve above goals, the principal investigator will translate the well-established design principles for photon/phonon-qubit hybrids (i.e. cavity and circuit quantum electrodynamics) to the proposed magnon-spin-qubit systems. Beyond these similarities, magnons also offer unique capabilities, such as condensation into superfluid-like, as well as, soliton-like modes, and inherent chiral propagation. The proposed research is thus expected to uncover fundamentally new device concepts unique to magnonic system, such as unidirectional chiral spin-spin coupling. Exploring such device concepts theoretically will also form an integral part of this proposal.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.