Quantum optics and sensing with diamond defects

嵌入固态材料中的单自旋代表了一种典型的量子系统，在低温下表现出几秒钟、几分钟甚至几个小时的量子力学行为。这种非凡的相干性为新一代技术提供了资源，这些技术利用量子力学的特性，如叠加和纠缠，来解决计算和信息安全方面的重要问题。与超导量子比特或俘获离子不同，这些固态系统坚固耐用，严格保持在晶体主体内，在室温下运行，并且可以很容易地与纳米制造的电路集成。虽然在控制单个自旋方面取得了显著进展，但一个突出的挑战是开发自旋之间可扩展的量子相干连接，使人们能够将它们连接到一个更大的网络中。拟议中的研究计划将追求一个关键的组成部分来应对这一挑战：在自旋和光子之间建立高效而连贯的量子界面，这将使遥远的自旋之间能够进行快速的光子中介相互作用。我们的方法使用与钻石中光学活性缺陷中心相关的自旋，并通过在光纤尖端形成的微腔来增强它们与光的相互作用。这种自旋-光子接口可以促进所谓的“量子中继器”的创建，以确保全球范围内的通信安全，甚至是最终的量子版本的互联网。 除了未来在量子信息科学中的应用外，自旋的量子态在计量学中也有应用：它们对局部磁场非常敏感。因此，每个自转都代表着一个原子尺度的传感器。我们研究的第二个重点将利用与钻石中的氮空位缺陷相关的自旋来研究纳米级磁性设备的动力学。我们将研究如何用自旋极化的电子电流来控制这些设备，感知产生的自旋波激发，并最终探索这些磁激发的量子化版本(“磁子”)是否可以为自旋之间的量子相干连接提供一种新的范式。除了磁子在量子技术中的潜在应用外，我们开发的技术将提供对纳米级磁现象的新见解，并直接应用于现代(经典)计算和通信硬件。因此，这一研究计划的结果可能会对长期和近期应用的信息技术产生影响。

Single spins embedded in solid-state materials represent a quintessential quantum system, exhibiting quantum mechanical behaviour over seconds, minutes, or even hours at cryogenic temperatures. This remarkable coherence is a resource for a new generation of technologies that exploit the features of quantum mechanics, such as superposition and entanglement, to solve important problems in computing and information security. In contrast to superconducting qubits or trapped ions, these solid-state systems are robust, rigidly held within their crystal host, operate at room temperature, and can be easily integrated with nano-fabricated circuitry. While remarkable advances have been made in controlling individual spins, an outstanding challenge is to develop quantum-coherent connections between spins that are scalable, enabling one to link them into a larger network. The proposed research program will pursue a key building block to meet this challenge: an efficient and coherent quantum interface between spins and photons, which will enable fast, photon-mediated interactions between distant spins. Our approach uses spins associated with optically-active defect centres in diamond, and enhances their interactions with light using microscopic cavities formed on the tip of optical fibres. This spin-photon interface could facilitate creation of so-called “quantum repeaters” to secure communication over global distances, or, ultimately, even a quantum version of the internet. In addition to their future applications in quantum information science, the quantum states of spins have applications in metrology: they are exquisitely sensitive to local magnetic fields. Each spin thus represents an atomic-scale sensor. The second focus of our research will use spins associated with the nitrogen-vacancy defect in diamond to study the dynamics of nanoscale magnetic devices. We will examine how these devices can be controlled with currents of spin-polarized electrons, sense the spin-wave excitations produced, and ultimately explore whether the quantized version of these magnetic excitations (“magnons”) could offer a new paradigm for quantum-coherent connections between spins. Beyond the potential applications for magnons in quantum technologies, the techniques we develop will offer new insight into nanoscale magnetic phenomena, with direct application to modern (classical) computation and communication hardware. The outcomes of this research program could thereby impact information technologies for both long- and near-term applications.