EAGER: Enabling Quantum Leap: Electrically tunable, long-distance coherent coupling between room temperature qubits mediated by magnons in low-dimensional magnets

非技术描述：量子力学的反直觉定律（在经典世界中无法观察到）为构建下一代信息处理、通信和传感技术提供了可能性，这些技术的性能远远超过当今的设备。量子现象非常容易受到与环境相互作用的影响，并且通常限于相互作用最小的超低温。与之形成鲜明对比的是，钻石的原子级缺陷与环境完全隔离，即使在环境条件下也表现出量子特性。因此，这种系统是创建室温量子器件的理想构建模块。然而，为了实现可扩展的室温量子器件，必须增加单个缺陷之间相互作用的范围，同时还必须具有打开和关闭相互作用的控制。该项目通过开发一种新型的金刚石缺陷混合材料平台来解决这些突出的挑战，该平台与磁性薄膜相结合，其中单个缺陷之间所需的远距离和可控量子相互作用是磁性介导的。该项目还旨在通过向量子物理、工程和材料科学领域的本科生和研究生提供跨学科培训，增强美国的量子工程人才队伍。技术描述：金刚石中的氮空位中心已成为构建量子技术的主要室温量子比特。然而，在相隔几十纳米的氮空位中心之外扩展相干耦合被证明是具有挑战性的。该研究项目旨在通过展示室温下氮空位量子比特自旋之间的电可调相干耦合，为这种材料挑战提供解决方案，这些自旋之间的距离接近微米。为此，提出了一个新的平台，其中氮空位中心之间的相干耦合是由限制在电控制的低维磁体中的磁振子介导的。该平台利用了最近的两项实验进展，即：(a)磁子-氮空位自旋耦合的强共振增强，以及(b)低维磁体的电场可调性增强。共振增强与磁振子的长距离输运相结合，使得介导远程相干耦合成为可能；而这些共振的电可调性为打开和关闭相干耦合提供了令人兴奋的可能性。特别是，该项目利用了这些以前无法获得的机会，将相干耦合的范围扩展到室温量子比特的最先进演示之外，并展示了按需量子门功能。拟议的研究为技术应用提供了机会，同时也为培训下一代量子技术专家和科学家提供了独特的教育机会。具体来说，该项目的成功完成为在环境条件下工作的量子技术构建可扩展平台提供了缺失的环节。另一方面，量子信息处理与自旋电子学的交叉也为学生和博士后的跨学科培训、新课程的开发以及向公众推广提供了新的机会。为此，该团队建议利用普渡大学现有的本科生研究经验项目，同时在nanoHub（最大的纳米技术在线资源）上发布在线研讨会，以便向更广泛的社区传播。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。

Nontechnical description: The counterintuitive laws of quantum mechanics (not observable in a classical world) offer the possibility to build next generation of information processing, communication and sensing technologies capable of far outperforming present-day devices. Quantum phenomena are extremely susceptible to interactions with the environment and are generally limited to ultralow temperatures, where interactions are minimal. In stark contrast, atomic-scale defects in diamond, being sufficiently isolated from the environment, exhibit quantum properties even at ambient conditions. Consequently, such systems are ideal building blocks for creating room temperature quantum devices. However, in order to realize scalable room temperature quantum devices, it is imperative to increase the range of interaction between individual defects, while also having the control to turn the interaction on and off. This project addresses these outstanding challenges by developing a novel hybrid material platform of diamond defects interfaced with thin magnetic films, where the required long-distance and controllable quantum interaction between individual defects is mediated magnetically. The project also aims to enhance the United States' quantum engineering workforce by providing interdisciplinary training to undergraduate and graduate students at the interface of quantum physics, engineering and materials science. Technical description: Nitrogen vacancy centers in diamond have emerged as the dominant room temperature quantum bit for building quantum technologies. However, scaling coherent coupling beyond Nitrogen Vacancy centers separated by few tens of nanometers has proven challenging. This research project aims to provide a solution to this materials challenge by demonstrating electrically tunable coherent coupling between Nitrogen vacancy qubit spins at room temperature, which are separated by near micrometer distances. For this purpose, a novel platform is proposed, where the coherent coupling between Nitrogen vacancy centers is mediated by magnons confined in electrically controlled low-dimensional magnets. The proposed platform takes advantage of two recent experimental advances, namely: (a) strong resonant enhancement of magnon-Nitrogen vacancy spin coupling, and (b) enhanced electric-field tunability of low-dimensional magnets. The resonant enhancement, in combination with the long-distance transport of magnons, allows for the possibility of mediating long range coherent coupling; while the electrical tunability of these resonances offers exciting possibility to turn the coherent coupling on and off. In particular, the project takes advantage of these previously unavailable opportunities to extend the range of coherent coupling beyond the state-of-the-art demonstrations for room temperature quantum bits, as well as, demonstrate an on-demand quantum gate functionality. The proposed research provides opportunities for technological applications, while it also offers unique educational opportunities for training the next generation of quantum technologists and scientists. Specifically, successful completion of the project provides the missing link towards building a scalable platform for quantum technologies working at ambient conditions. On the other hand, the intersection of quantum information processing and spintronics also offers new opportunities for interdisciplinary training of students and postdocs, development of new courses, and outreach to the public. For this purpose, the team proposes to leverage existing undergraduate research experience programs at Purdue, along with posting of online seminars on nanoHub (the largest online resource of nanotechnology) for dissemination to a broader community.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.