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Prof. Dr. Dominik Zumbühl

Department of Physics
Profiles & Affiliations

Projects & Collaborations

27 found
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Ultra high precision electron beam lithography system for nanodevice and nanostructures definition

Research Project  | 6 Project Members

In the last decades nano- and quantum-science have been steadily growing in large part also thanks to the availability of ever more advanced processing, manipulation, and imaging tech-niques. Specifically, nanofabrication has been the leading enabler of experiments and devices, in which quantum mechanics play a key role. The University of Basel is nationally and internationally recognized as a leader innanoscience and nanotechnology. It was the leading house of the National Center in Competence and Re-search (NCCR) on Nanoscience, which later became the Swiss Nanoscience Institute (SNI). The University of Basel is leading the NCCR SPIN for the realization of spin qubits in Silicon and is also co-leading the NCCR QSIT on Quantum Science and Technology (with ETHZ as Leading House). The present proposal to the SNF R'Equip scheme is a joint effort of six principal investigators (PIs) in the physics department of the University of Basel, who work on current topics in quantum- and nano-science. The PIs, who submit this proposal together, do research that relies on the availability of state-of-the-art fabrication tools, such as an electron beam lithography (EBL) system. The proposal makes the case for the purchase of an ultra-high precision EBL system that combines high resolution, tunable acceleration voltages, different write-field size, ultra-high precision alignment, proximity correction, and mechanical stability. This combination is unique and crucial for the University of Basel to stay at the forefront of nano-science and technology. The system will be installed in the new clean room shared between the University of Basel and the Department of Biosystem Science and Engineering of the ETH. Therefore, the purchased system will be available for the users of the clean-room.

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NCCR SPIN Spin Qubits in Silicon

Research Project  | 11 Project Members

The main objective of NCCR SPIN is to develop reliable, fast, compact, scalable spin qubits in silicon and germanium. The vision is to control single spins with electrical means. Fast control of individual spins can be achieved with electrical pulses via a spin-orbit interaction. The spin-orbit interaction is either inherent (hole spin) or synthetic (electron spin in a magnetic field gradient). It also allows neighbouring spins to be coupled together electrically via superconducting resonators or floating gates. The specific aim of the first phase of the project is to develop the silicon spin qubits and spin-spin coupling strategies. Beyond fundamental research on the qubits and their architecture, there are further research efforts in many related areas of quantum computing, such as quantum error correction, quantum information, quantum algorithms and software, qubit control electronics and cryo-MOS, NISQ applications and algorithms. The long term goal is fault-tolerant universal quantum computing with a large number of logical qubits. The NCCR SPIN team consists of researchers from the University of Basel , IBM Research - Zurich , ETH Zurich , and EPF Lausanne . The team members are experts from various disciplines, such as quantum physics, materials science, engineering and computer science. In addition to the collaboration between academia and industry, the NCCR SPIN is characterized by very close links between theory and experiment as well as physics, materials science and engineering. The home institution is the University of Basel .

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QUSTEC PhD fellowship - Spectroscopy of Subgap States in Semiconducting Nanowires with Proximitized Superconductivity

Research Project  | 4 Project Members

Original Title: Quantum transport in superconductor-semiconductor nanowire hybrid devices with axially built-in quantum dots as spectrometers Abstract: The project is motivated by the recent excitement of the appearance of topological phases and Majorana bound states (MBSs) in semiconducting nanowires (NWs) with strong spin-orbit interaction (SOI) coupled to a superconductor (SC) in magnetic field. To unravel the emergence of MBSs in single and coupled NWs, we develop new probes with which the proximity gap and proximity-induced bound states can be quantified. Our approach is based on measuring both DC and AC transport, the latter also at GHz frequencies using reflectometry. As a complementary test, we can also study the microwave radiation in the GHz domain emitted by the quantum device. With the current project we aim to deepen our understanding of the superconductive proximity effect in a NW with strong SOI by studying the evolution of the gap spectroscopically. For the latter we exploit quantum dots (QDs) as spectrometers. Here, the QDs are established by heteroepitaxy during growth. This is done in collaboration with Prof. Lucia Sorba from CNR-Nano at Pisa, where the InAs NWs are grown (see figure). These QDs are very promising due to the large confinement potential. We further plan to test different SCs beyond Al, e.g. Pd and MoRe, and optimize the evaporation together with collaborators from the Niels-Bohr Institute in Copenhagen. p.s. in the meantime the material system was changed to 2D InAs quantum proximitized from above by a thin Al layer. This material is provided by the Mafra group (Purdue Univ. USA).

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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.