CAREER: Spin-Magnon based Hybrid Quantum Devices

量子系统显示出令人着迷的反直觉的叠加特性，即同时处于多个态的能力，以及纠缠，即发展远距离多体关联的能力。这些特性提供了建立量子技术的机会，例如传感、通信和信息处理，具有经典领域无法实现的能力。近年来，在这一承诺的推动下，在设计和控制各种单独的量子系统方面取得了巨大的进展。其中，绝缘材料中的自旋缺陷，即微观自旋量子比特(量子比特)尤其有希望。自旋通过其磁偶极矩与环境相互作用：这一事实被用来以前所未有的空间分辨率和灵敏度对磁场进行量子传感。另一方面，存在自旋量子比特的典型材料中的环境会产生微弱的磁场，因此编码在自旋量子比特中的量子态可以长时间存活，这一事实使自旋量子比特成为量子存储和信息处理的候选对象。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，以：(I)感测磁场以外的信号，用于开发新型量子传感器；以及(Ii)可控制地相互作用，超越少数近邻放置的自旋量子比特，同时保持个人寻址能力，用于量子信息处理。然而，这已经被证明是具有挑战性的，因为缺乏一个可以控制并强烈耦合到自旋量子比特以及广泛的外部信号的介体。在这个项目中，首席研究员将利用磁子(即磁体中的集体激发)作为一种全新的媒介来应对这一挑战。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，培训本科生、研究生和行业专业人员，以加强美国的量子智能劳动力。提出的研究旨在通过理论和原理验证实验相结合的方法来解开新型的磁振子自旋-量子比特混合器件。特别是，首席调查员将追求以下设备类型。(A)传感类装置--这些装置的中心目标将是增强自旋量子比特对电场、温度等信号的传感能力。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)信息处理类设备--这些设备的中心目标将是解决为自旋量子比特设计可扩展的信息处理结构的挑战，在这种结构中，量子比特可以跨不同的长度尺度相干耦合，同时保持局部可寻址能力。为此，我们将展示通过电泵浦设计的磁振子模式，将经典信号相干耦合到局部自旋量子比特的理论方案和原理验证实验。此外，还将通过设计磁共振模式来开发在量子区域中自旋量子比特和磁子之间传输信息的方案。为了实现上述目标，首席研究人员将把光子/声子-量子比特混合体(即腔和电路量子电动力学)的成熟设计原理转化为所提出的磁振子-自旋-量子比特系统。除了这些相似之处，磁子还提供了独特的能力，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，这项拟议的研究有望从根本上揭示磁子系统独有的新装置概念，如单向手性自旋-自旋耦合。从理论上探索这样的设备概念也将成为这项提议的组成部分。该奖项反映了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。

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.