QII-TAQS: Quantum Devices with Majorana Fermions in High-Quality Three-Dimensional Topological Insulator Heterostructures

量子计算机在安全和新材料开发等重要领域有着巨大的潜力。然而，走向强大的量子计算的进展缓慢，部分原因是量子计算机的基本逻辑单元-量子比特的一致性问题。拓扑绝缘体是物质的主要状态，有望防止粘性损失，但由于材料质量问题尚未得到应用。这个项目致力于通过开发新的方案来实现、检测和操纵拓扑量子计算机的构建块，即拓扑量子计算。基于高质量拓扑绝缘体的异质结构中的Majorana费米子。这些研究利用研究人员的跨学科专业知识(在物理、材料科学和电气工程方面)，并与研究人员的教育计划相结合，包括在协作环境中培训本科生和研究生，以成为量子劳动力的宝贵补充。研究人员将开发关于量子材料、现象和计算及其相互作用的专门课程。量子计算的兴奋将通过针对年轻一代和代表性较低的少数群体的新颖推广活动来传播，包括通过YouTube的社交媒体努力，以及与当地学校和博物馆的英语-西班牙语双语推广。这些努力建立在研究人员现有计划的基础上，旨在扩大对教育和研究的参与。该项目旨在建立一个材料平台，以发展实用的拓扑量子计算。由于环境和量子态本身的操纵，传统的量子比特受到退相干的影响。人们认为，拓扑量子材料的出现将使量子比特的实现成为可能，这些量子比特在拓扑上受到保护，不受这两种类型的退相干的影响。实现拓扑量子计算的一个重要平台是通过三维拓扑绝缘体表面的Majorana费米子来实现这一目标，然而，由于材料质量问题，以前实现这一目标的努力受到阻碍。多学科团队将使用他们最近展示的基于拓扑绝缘体的范德华异质结构和分子束外延生长异质结构形式的互补性高质量拓扑绝缘体平台，创建与金属、绝缘体、铁磁体和超导体一起的3D拓扑绝缘体的设备配置。这两种方法基于对非手性和手性Majorana费米子的几种不同的理论预测、量子现象的建模和实验签名的测试，使用相同的构建块串联用于各种Majorana费米子的实现。对各种实现方式进行了比较，并以高温拓扑超导体的形式探索了一条替代路线。这些实验研究和设备实现将与团队中的材料科学家和工程师合作完成，利用计算专家的材料建模和模拟专业知识。这样的平台提供了纳米线Majorana费米子的替代方案，并承诺提供高达毫米的卓越相干长度，潜在地向拓扑量子计算机的发展提供了重大飞跃。该奖项反映了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。

Quantum computers have great potential in important areas such as security and the development of new materials. However, progress toward robust quantum computing has been slow due in part to the issue of coherence of the fundamental logic unit of the quantum computer - the qubit. Topological insulators are the primary state of matter promising protection from loss of coherence but have not yet found application due to materials quality issues. This project works toward "topological quantum computing" by developing novel schemes for realization, detection, and manipulation of the building blocks of a topological quantum computer, viz. Majorana fermions, in heterostructures based on high-quality topological insulators. These studies take advantage of the cross-disciplinary expertise of the investigators (in physics, materials science, and electrical engineering), and integrate with the investigators' education plan, involving the training of undergraduate and graduate students in a collaborative setting to be valuable additions to the quantum workforce. Special courses will be developed by the investigators on quantum materials, phenomena, and computing and their interplay. The excitement of quantum computing will be communicated through novel outreach efforts targeted at the younger generation and underrepresented minority groups, including social media efforts through YouTube and bilingual English-Spanish outreach with local schools and museums. These efforts build on already existing programs of the investigators and aim to broaden participation in education and research.This project aims to establish a materials platform toward the development of practical topological quantum computing. Conventional qubits suffer from decoherence due to the environment and the manipulation of the quantum state itself. It is thought that the advent of topological quantum materials will allow the realization of qubits that are topologically protected from both types of decoherence. An important platform in which to realize topological quantum computing is through Majorana fermions on the surface of 3D topological insulators; however, previous efforts to experimentally realize this goal have been impeded by materials quality issues. The multidisciplinary team will use their recently demonstrated complementary high-quality topological insulator platforms in the form of topological insulator-based van der Waals heterostructures and molecular-beam epitaxially-grown heterostructures to create device configurations of 3D topological insulators together with metals, insulators, ferromagnets, and superconductors. The two approaches are used in tandem toward a variety of Majorana fermions realizations using the same building blocks, based on several different theoretical predictions of both non-chiral and chiral Majorana fermions, modeling of quantum phenomena, and testing of experimental signatures. The various realizations will be compared and an alternative route explored in the form of high-temperature topological superconductors. These experimental studies and device realizations will be done in collaboration with the materials scientists and engineers on the team, taking advantage of the materials modeling and simulation expertise of the computational expert. Such a platform provides an alternative to nanowire Majorana fermions, the prevalent topological quantum computing platform, and promises superior coherence lengths up to millimeters, potentially providing a significant leap toward the development of a topological quantum computer.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.