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

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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.