Collaborative Research: A Fast, Scalable, and High-Fidelity Spin Entangling Gate On-A-Chip

通过利用独特的量子力学效应，如量子叠加和纠缠，可以创建指数快速的量子计算机，无条件安全的量子网络和超精确的量子传感器。然而，为了实现这些量子优势，需要大量量子比特之间的受控相互作用，这是极难实现的。扩大量子系统的一种方法是使用由光子形成的总线将多个小规模量子模块互连。该计划旨在开发一种芯片集成的量子光子电路，可以以前所未有的纠缠率和保真度光学互连电子自旋。为了确定性地将两个或多个电子自旋与光子电路耦合，主要研究人员将通过将自下而上的材料合成与自上而下的器件制造相结合来探索新的混合光子学平台。这种能力将为集成光子芯片中量子电路的可扩展制造铺平道路，并为基于固态自旋和光子的量子信息处理开辟新的机会。除了研究部分外，该计划还将包括培训量子科学和技术领域的下一代科学家和工程师，以及大力开展外展工作，教育K-12学生并扩大STEM领域的参与。技术描述：在固态量子技术的众多量子位平台中，钻石中的缺陷中心表现出一些最好的自旋相干特性。缺陷中心的电子和核自旋都可以用作量子比特，它们可以通过直接偶极耦合相互作用。然而，由于偶极相互作用的短范围，在按比例放大该系统中存在基本限制。另一方面，光子是调解远程纠缠的理想载体。它们是高度通用的互连，可以在从微米到公里的多个距离尺度上桥接量子相互作用。为了实现基于自旋的量子技术的全部潜力，需要光子介导的纠缠具有足够的速率和保真度，这是难以实现的基于自发辐射的传统纠缠方案。该研究旨在开发一种新的基于腔散射的纠缠方案，这将显着提高可实现的纠缠速率和保真度。为了确定性地将两个或多个自旋与不同的腔体耦合，主要研究人员将通过将自下而上的材料合成与自上而下的纳米纤维结合起来，探索一种新的器件工程方法。具体来说，他们将开发一种新技术，在成熟的光子材料氮化硅上生长纳米金刚石。在材料生长之后，研究人员将使用自上而下的纳米光子工程，通过将纳米金刚石中硅空位中心的单电子自旋与氮化硅纳米腔耦合来开发相干自旋光子界面。结合这两种能力，研究人员将开发一个集成的量子光子电路，以产生光子介导的自旋纠缠，具有前所未有的纠缠率和保真度。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

By harnessing uniquely quantum mechanical effects such as quantum superposition and entanglement, it becomes possible to create exponentially fast quantum computers, unconditionally secure quantum networks, and ultraprecise quantum sensors. However, to achieve these quantum advantages requires controlled interactions among a large number of quantum bits, which is extremely difficult to realize. One way to scale up a quantum system is to interconnect multiple small-scale quantum modules using a bus formed by optical photons. This program aims to develop a chip-integrated quantum photonic circuit that can optically interconnect electron spins with unprecedented entanglement rate and fidelity. To deterministically couple two or multiple electron spins with the photonic circuit, the principle investigators will explore a new hybrid photonics platform by merging bottom-up material synthesis with top-down device fabrication. This capability will pave the way towards scalable manufacture of quantum circuit in an integrated photonics chip and open new opportunities in both solid-state spin and optical photon based quantum information processing. In addition to the research component, this program will include the training of the next generation of scientists and engineers in quantum science and technology, as well as a strong outreach effort to educate K-12 students and broaden participation in STEM fields.Technical Description:Among the many qubit platforms for solid-state quantum technologies, defect centers in diamond exhibit some of the best spin coherence properties. Both the electron and nuclear spins of the defect centers can be used as qubits, and they can interact with each other through direct dipolar coupling. However, there is a fundamental limit in scaling up this system, due to the short range of the dipolar interactions. On the other side, photons are ideal carriers to mediate remote entanglement. They are highly versatile interconnects and can bridge quantum interactions over multiple distance scales from micrometers to kilometers. To attain the full potential of spin-based quantum technologies requires photon-mediated entanglement with sufficient rate and fidelity, which is difficult to achieve with traditional entanglement schemes based on spontaneous emission. The proposed research aims to develop a new entanglement scheme based on cavity scattering, which will significantly boost the achievable entanglement rate and fidelity. To deterministically couple two or multiple spins with different cavities, the principal investigators will explore a new device engineering approach by merging bottom-up material synthesis with top-down nanofabrication. Specifically, they will develop a novel technique to grow nanodiamonds on a mature photonic material, silicon nitride. Following the material growth, the researchers will use top-down nanophotonic engineering to develop a coherent spin-photon interface by coupling single electron spins of silicon-vacancy centers in nanodiamonds with silicon nitride nanocavities. Combining both capabilities, the researchers will develop an integrated quantum photonic circuit to generate photon-mediated spin entanglement with an unprecedented entanglement rate and fidelity.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.