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Theoretische Physik Mesoscopics (Loss)

Projects & Collaborations

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QLSI : Quantum Computing - Large-Scale Integration

Research Project  | 1 Project Members

We propose a 4-year project QLSI, Quantum Large Scale Integration in Silicon, which objective is to demonstrate that silicon spin qubits are a compelling platform for scaling to very large numbers of qubits. Our demonstration relies on four ingredients: - Fabrication and operation of 16-qubit quantum processors based on industry-compatible semiconductor technology; - Demonstration of high-fidelity (>99%) single- and two-qubit gates, read-out and initialization; - Demonstration of a quantum computer prototype, with online open-access for the community (up to 8 qubits available online); - Documentation of the detailed requirements to address scalability towards large systems >1000 qubits. To achieve these results, our consortium brings together an unrivalled multidisciplinary team of European groups in academia, RTOs and industry working on silicon-based quantum devices. These groups are committed to playing an active part in developing the industrial ecosystem in silicon-based quantum technologies. QLSI is structured in three enabling toolboxes and one demonstration and scalability activity: - the semiconductor toolbox brings together skills from the semiconductor industry such as fabrication, high throughput test and CAD (computer aided design) with the expertise of the physics community; - the quantum toolbox gathers skills from the physics community on spin and quantum properties of Si based nanostructures and on quantum engineering from theory and experience perspectives; - the control toolbox gathers teams with instrumentation skills ranging from RF signal generation, automation and set up of high throughput characterization at low temperature. The toolboxes will generate stand-alone beyond the state-of-the-art results and will generate inputs to feed the demonstrator and scalability activity, which will integrate devices, hardware and software solutions to create an online open access demonstrator, to perform hybrid computation and to analyze scalability.

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Majorana Fermions and Parafermions in Topological Insulators

Research Project  | 4 Project Members

Topological insulators and topological superconductors (TSCs) constitute a new class of quantum materials with a gapped bulk spectrum and gapless surface states. Due to topology, the appearance of these surface states is remarkably robust against external perturbations. In this proposal, we want to discover feasible ways to identify and manipulate Majorana fermions (MFs) and parafermions (PFs) in topological insulator hybrid structures. MFs and PFs are fractional excitations that appear as boundary states of TSCs. They are known to be building blocks for qubits of a topological quantum computer. The system we have identified as the most promising platform for this task is a bilayer quantum spin Hall insulator in proximity to an ordinary s-wave superconductor. In that nanostructure, we expect a complex interplay between helicity, intra- and inter-layer Coulomb interaction, disorder, and superconducting order. The Basel and Würzburg groups, involved in the project, nicely complement each other in terms of theoretical skills (Basel: quantum computing; Würzburg: quantum transport) and the experimental ability (at Würzburg) to actually implement this challenging system in the laboratory. We are therefore confident that we will develop innovative ideas to generate and control MFs and PFs at will within this consortium.

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TOPSQUAD / TOPOLOGICALLY PROTECTED AND SCALABLE QUANTUM BITS

Research Project  | 4 Project Members

Our vision is to enable the world of quantum computing through an unprecedented stable and scalable manyqubi system. This platform will allow us to establish important scientific breakthroughs such as the observation of Majorana bound states, which can lead to the new field of non-Abelian many-body physics. A universal quantum computer can be exponentially faster than classical computers for certain scientific and technological applications. This long-awaited innovation can help solve many global challenges of our time related to health, energy and the climate, such as quantum chemistry problems in order to design new medicines, material property prediction for efficient energy storage, big data handling problems, needed for complexity of climate physics. Such a quantum computer has not yet been realized because of qubit fragility and qubit scalability. The output of TOPSQUAD lays the foundation for universal quantum computing with stable and scalable qubits: We will address qubit fragility by creating topological states, which are insensitive to decoherence. We will address qubit scalability by developing waferscale fabrication technology, using CMOS-compatible processes. After TOPSQUAD, existing integrated-circuit technology can then serve to scale up from individual qubits to 100,000s. These two approaches have not been combined within a single system, but our recent results show that we can be the first to address the key challenges: 1. For the first time we will synthesise Ge wires on silicon wafers using scalable CMOS-compatible processes. 2. We will devise an unprecedented silicon system with the required topological properties: Ge wires with a silicon shell. 3. The thin Si shell will suppress metallization, thus avoiding the destruction of topological states by proximityinduced superconductivity, a typically overlooked problem. With this, TOPSQUAD can realize a scalable, CMOS-compatible, topologically protected system.

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Quantum theory of condensed matter: spin effects in nanostructures and quantum information

Research Project  | 4 Project Members

The proposed research covers and interconnects multiple topics from the fields of quantum computing and quantum condensed-matter theory. It contributes to the long term goal of finding realistic architectures that allow the coherent manipulation of solid state systems at the quantum level. Since this goal necessarily involves the study of complex many-body systems, our research goes across many subfields of modern condensed matter and solid state theory and uses a very broad range of sophisticated technical tools.The strategy we pursue encompasses the refinement of the well-established scheme of spin-based quantum computing, as well as efforts to discover novel and realistic platforms that allow the storage and manipulation of quantum information. In view of the desired industrial feasibility and scalability of the results, we focus on the solid state as the basis of our research. Exciting and promising new materials will be examined and their suitability for quantum information processing will be evaluated. Moreover, we will study intriguing issues that are also of interest in fundamental research, ranging from exotic types of topological quantum phases to non- equilibrium dynamics, with focus on spin effects in semiconducting, superconducting, and insulating magnetic nanostructures. Also these fundamental aspects of our proposal are targeted on the ability to gain access to the quantum world. In particular, we plan to work on the following topics:2.A Quantum information and surface code2.B Spin qubits in Si and Ge nanowires2.C Majorana fermion qubits and hybrid spin qubits2.D Stability of topological excitations and qubits2.E Proximity effect in semiconducting nanostructures2.F Topological magnonics2.G Quantum effects of magnetic Skyrmions

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G. H. Endress Postdoc-Cluster

Research Project  | 5 Project Members

Das Departement für Physik der Philosophisch-Naturwissenschaftlichen Fakultät der Universität Basel und das Physikalische Institut der Fakultät für Mathematik und Physik der Albert Ludwigs-Universität Freiburg im Breisgau errichten partnerschaftlich ein neues Exzellenzzentrum mit den Forschungsschwerpunkten "Quantum Science and Quantum Computing" unter dem Dach von Eucor - The European Campus . Als tragende Säule dieses Exzellenzzentrums wird ein grenzüberschreitender Postdoc-Cluster zwischen den Universitäten Basel und Freiburg aufgebaut. Primäre Ziele des zukünftigen Postdoc-Clusters sind die hochwertige Ausbildung der Postdocs für den akademischen als auch wirtschaftlichen Arbeitsmarkt und die Positionierung als führende Forschungseinrichtung auf dem Gebiet "Quantum Science and Quantum Computing", im Speziellen durch die verstärkte grenzüberschreitende Zusammenarbeit im Dreiländereck Deutschland-Frankreich-Schweiz. Das Exzellenzzentrum "Quantum Science and Quantum Computing" wird von der Georg H. Endress Stiftung finanziell unterstützt.

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NCCR QSIT: Outreach and Research Project based on Quantum Error Correction

Research Project  | 1 Project Members

This project presents quantum error correction and other topics in quantum computation research in a way that is accessible to the public. They will be able to learn about the science through blog posts and videos, as well as contribute to the research themselves. The latter is done through games and puzzles, primarily for iOS and Android devices. All services will be provided in German and and English. The project will also do world leading research in the field of quantum error correction. This will be adjacent to the research in the outreach project. The work will be explained to the public through the blog and videos, provided another way that they can engage with the research.