Spin-based probes of magnetic dynamics in the few-magnon regime

孤立自旋基本粒子的量子化磁矩为磁场和磁性材料提供了一种独特的、敏感的纳米级探测器。特别是，与金刚石中的光学活性缺陷氮空位(NV)中心相关的长寿命自旋与磁场如此巧妙地调谐，以至于它应该能够探测到近端铁磁体中磁激发的量子零点涨落，并观察到绝对磁振子吸收和发射中的量子不对称。这种基于NV的传感器为磁性材料的热力学打开了一扇新的窗口，并将使我们能够探索目前尚不清楚的通过自旋电流注入进行磁振子冷却的极限。*同时，自旋和磁性材料之间的相互作用代表着量子信息科学的一种资源：磁子被提出用来调节自旋量子比特之间强烈的、可控的相互作用。仔细研究NV自旋与近基态磁振子相互作用的演化，应该会揭示自旋-磁振子纠缠的特征，这代表着实现量子信息的磁非介质门的第一步。这样的体系结构可以将固态自旋的长相干时间与比现代超导系统高出数量级的量子比特间隔结合在一起，潜在地为未来量子信息处理在优化、分子模拟和其他领域的应用开辟了一条道路，使加拿大的企业和政府受益。要进行这样的实验，需要将能够隔离和检测NV自旋的共焦显微镜与能够将样品温度保持在接近或低于磁激发~150mK量子的稀释冰箱相结合。我们的合作已经可以使用共焦显微镜和稀释冰箱；这项RTI提案将为将它们整合到单一实验中所需的部件提供资金。需要一种特殊的低温兼容显微镜物镜和低温纳米定位器来取代它们的室温定位器；必须在低温恒温器中小心地安装微波和直流电子线来控制样品和定位器；光学元件将激励和荧光传入和传出低温恒温器；定制安装件将支持样品和组件。因此，所要求的设备利用了相当多的现有资源，创建了一种高度专业化的设备，能够从事纳米磁学和量子磁振学方面的尖端研究。

Isolated spins the quantized magnetic moments of fundamental particles offer a uniquely sensitive and nanoscale probe of magnetic fields and magnetic materials. In particular, the long-lived spin associated with the nitrogen-vacancy (NV) centre, an optically active defect in diamond, is so exquisitely attuned to magnetic fields that it should be able to detect the quantum zero point fluctuations of magnetic excitations so-called magnons in a proximal ferromagnet, and observe the quantum asymmetry in magnon absorption and emission for absolute magnon thermometry. Such an NV-based sensor opens a new window into the thermodynamics of magnetic materials, and will permit us to explore the limits to magnon cooling via spin current injection, which currently remain unknown. ******At the same time, interactions between spins and magnetic materials represent a resource for quantum information science: magnons have been proposed to mediate strong, controllable interactions between spin qubits. Careful investigation of the evolution of an NV spin interacting with a near-ground state magnon bath should reveal signatures of spin-magnon entanglement, representing the first step towards realization of magnon-mediated gates for quantum information. Such an architecture could combine the long coherence times available in solid-state spins with a qubit spacing orders of magnitude denser than modern superconducting systems, potentially opening an avenue for future quantum information processing applications in optimization, molecular simulation and others, benefitting Canadian business and government.******To pursue such experiments requires combining a confocal microscope capable of isolating and detecting NV spins with a dilution refrigerator capable of maintaining a sample temperature near or below the quantum of magnetic excitation ~ 150 mK. Our collaboration already has access to a confocal microscope and a dilution refrigerator; this RTI proposal would fund the components needed to integrate them into a single experiment. A specialty cryogenically-compatible microscope objective and cryogenic nano-positioners are needed to replace their room-temperature counterparts; microwave and DC electronic lines must be carefully installed in the cryostat to control the sample and positioners; optical components will route excitation and fluorescence into and out of the cryostat; custom mounts will support the sample and components. The requested equipment thus leverages considerable existing resources to create a highly specialized apparatus capable of pursuing cutting edge research in nanomagnetism and quantum magnonics.