RAISE-TAQS: Topologically-Engineered Graphene Nanoribbon-based Quantum Systems

非技术描述：该项目的目标是从石墨烯纳米带(GNR)制造可操作的量子比特(Qubit)。量子比特是为密码学、模拟和各种其他计算任务等目的操作量子信息的设备的构建块。由于量子力学的非凡性质，人们预计量子信息设备(如量子计算机)的计算能力将远远超过传统经典计算机所能实现的能力。GNR(非常窄的石墨烯条带)是一个令人兴奋的创建量子比特的新平台，因为它们具有优异的电子、热和机械性能，并且可以从“自下而上”(即，逐个分子)高效地制造出原子精度。该项目的主要思想是通过使单个电子被捕获在化学工程GNR主干上的预定位置，将量子比特纳入GNR。由于GNR是分子级的结构，以这种方式排列的量子比特可能会产生尺寸更小、密度更高、结构灵活的量子设备，这是任何其他量子比特平台都无法比拟的。这个项目的一个主要焦点是合成这种基于GNR的量子比特，并使用包括扫描隧道显微镜和原子力显微镜在内的技术在原子尺度上对它们进行表征。在这些测量结果的基础上，选择合适的GNR量子比特候选者，将其整合到设计用于测量其量子性质的设备中。通过这一过程评估了基于GNR的量子比特作为一种新的量子信息平台的可行性。该项目更广泛的影响在于其强大的教育和推广部分，以及它为研究生、本科生和高中生提供高水平的科学培训，为他们在科学、技术、工程和数学(STEM)领域的职业生涯做好准备。量子科学家接受的培训是如何以新的跨学科方式将化学、材料科学和工程学结合起来。加州社区学院系统还被该项目作为招收STEM专业的有用渠道，这些专业更好地代表了我们国家的人口结构。该项目包含了一个现实的计划，即与旧金山湾区的一所社区学院合作，以开发一种新的量子信息课程，社区大学生可以使用该课程，允许他们将自己的学分转移到加州大学系统，并为他们创造参与尖端研究的新机会。技术描述：该项目的主要目标是评估一种新型的石墨烯纳米带(GNR)系统是否适合作为量子信息设备平台。GNR中的量子比特功能源于这个研究团队的研究人员最近的一项发现，即GNR可以承载每个包含一个电子自旋的拓扑保护界面态。这些拓扑界面可以在分子水平上进行工程设计，为控制基于GNR的纳米结构中的电子和自旋行为提供了一种新的方法。本项目选择了双界面GNR几何结构，将两个拓扑界面态放置在非常接近的位置，从而允许所产生的单态/三态自旋组态提供量子比特功能(类似于Si和GaAs双量子点的单态/三态量子位子空间)。由于石墨烯具有非常理想的电子、热和机械性质，GNR量子比特有望具有较长的退相干时间，在非常高的堆积密度下工作，并且非常适合于设备。成熟的自下而上的合成方法还允许通过高效的自组装过程来制造原子精确的GNR结构。这个项目由一个跨学科的研究团队执行，该团队由三名在化学、材料科学和电气工程方面有实力的研究人员组成。费舍尔领导了该项目基于化学的努力，以设计自组装成拓扑GNR量子比特的前体分子。M.F.Crommie领导了基于材料科学的努力，使用扫描探针显微镜来表征由此产生的量子比特结构的局部电子和自旋性质。J·博科领导了将合适的GNR量子比特系统整合到量子设备中进行功能评估的努力。这个项目解决的基本问题包括：拓扑GNR界面态是否可以耦合到多自旋量子比特中心，初始化为定义明确的量子态，并有效地读出。通过对GNR化学结构的原子精确操纵，探索了界面态杂化效应和现场库仑排斥之间的竞争，从而为量子自旋工程提供了与量子信息应用相关的新的物理机制。计划采用新的耦合GNR量子比特的方法，包括通过电子纳米设备诱导量子比特之间的纠缠，以及通过电子纳米设备寻址单个GNR量子比特，评估GNR作为量子信息平台的可行性。这一奖项反映了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。

Non-technical description: The goal of this project is to make operational quantum bits (qubits) from graphene nanoribbons (GNRs). Qubits are the building blocks of devices that manipulate quantum information for purposes such as cryptography, simulations, and a variety of other computational tasks. Due to the extraordinary properties of quantum mechanics, quantum information devices (such as quantum computers) are expected to perform calculations significantly beyond what conventional classical computers can ever hope to do. GNRs (which are very narrow strips of graphene) are an exciting new platform for creating qubits because they have excellent electronic, thermal, and mechanical properties, and they can be efficiently fabricated from 'the bottom-up' (i.e., molecule-by-molecule) with atomic precision. The main idea of this project is to incorporate qubits into GNRs by causing individual electrons to be trapped at predetermined locations along the backbone of chemically-engineered GNRs. Because GNRs are molecule-scale structures, qubits arranged in this way could potentially yield quantum devices having reduced size, increased density, and structural flexibility that is unmatched by any other qubit platform. A major focus of this project is to synthesize such GNR-based qubits and to characterize them at the atomic-scale using techniques that include scanning tunneling microscopy and atomic force microscopy. Based on the results of these measurements, suitable GNR qubit candidates are chosen for incorporation into devices designed to measure their quantum properties. The viability of GNR-based qubits as a new quantum information platform is evaluated through this procedure. The broader impacts of this project lie in its strong education and outreach components and the fact that it provides high-level scientific training to graduate students, undergraduates, and high school students, preparing them for careers in science, technology, engineering, and math (STEM) fields. Quantum scientists are trained in how to combine chemistry, material science, and engineering in new interdisciplinary ways. The California community college system has additionally been targeted by this project as a useful conduit for recruiting new STEM majors who better represent the demographics of our nation. This project incorporates a realistic plan to partner with a Bay Area community college in order to develop a new quantum information curriculum that is accessible to community college students, that allow them to transfer their credits to the University of California system, and create new opportunities for them to become involved in cutting-edge research. Technical description: The main goal of this project is to evaluate a new type of graphene nanoribbon (GNR) system for suitability as a quantum information device platform. Qubit functionality in GNRs arises from a recent discovery made by the investigators of this research team that GNRs can host topologically-protected interface states that each contain a single electron spin. These topological interfaces can be engineered at the molecular level and provide a new method for controlling electronic and spin behavior in GNR-based nanostructures. A double-interface GNR geometry has been chosen for this project that places two topological interface states in close proximity, thus allowing the resulting singlet/triplet spin configurations to provide qubit functionality (analogous to the singlet/triplet qubit subspace of Si and GaAs double-quantum-dots). Due to graphene's highly desirable electronic, thermal, and mechanical properties, GNR qubits are expected to have long decoherence times, to function at very high packing density, and to be very device-compatible. Established bottom-up synthesis methods additionally allow atomically-precise GNR structures to be fabricated via highly efficient self-assembly processes. This project is performed by an interdisciplinary research team comprised of three investigators with strengths in chemistry, material science, and electrical engineering. F. Fisher heads the project's chemistry-based efforts to design precursor molecules that self-assemble into topological GNR qubits. M. F. Crommie heads material science-based efforts to characterize the local electronic and spin properties of resulting qubit structures using scanned probe microscopy. J. Bokor heads efforts to incorporate suitable GNR qubit systems into quantum devices for functional evaluation. Fundamental questions addressed by this project include whether topological GNR interface states can be coupled into multi-spin qubit centers, initialized into well-defined quantum states, and efficiently read out. The competition between interface state hybridization effects and on-site Coulomb repulsion is explored through atomically-precise manipulation of the GNR chemical structure, thus presenting new physical regimes for quantum spin engineering that are relevant for quantum information applications. New methods of coupling GNR qubits are planned, including ideas for inducing entanglement between qubits and for addressing individual GNR qubits via electronic nanodevices, assessing the viability of GNRs as a quantum information platform.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.