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Subject: technology × WGL Institute: IHP ×

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    Gate-controlled quantum dots and superconductivity in planar germanium
    ([London] : Nature Publishing Group UK, 2018) Hendrickx, N.W.; Franke, D.P.; Sammak, A.; Kouwenhoven, M.; Sabbagh, D.; Yeoh, L.; Li, R.; Tagliaferri, M.L.V.; Virgilio, M.; Capellini, G.; Scappucci, G.; Veldhorst, M.
    Superconductors and semiconductors are crucial platforms in the field of quantum computing. They can be combined to hybrids, bringing together physical properties that enable the discovery of new emergent phenomena and provide novel strategies for quantum control. The involved semiconductor materials, however, suffer from disorder, hyperfine interactions or lack of planar technology. Here we realise an approach that overcomes these issues altogether and integrate gate-defined quantum dots and superconductivity into germanium heterostructures. In our system, heavy holes with mobilities exceeding 500,000 cm2 (Vs)−1 are confined in shallow quantum wells that are directly contacted by annealed aluminium leads. We observe proximity-induced superconductivity in the quantum well and demonstrate electric gate-control of the supercurrent. Germanium therefore has great promise for fast and coherent quantum hardware and, being compatible with standard manufacturing, could become a leading material for quantum information processing.
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    Cross-polarization effects in sheared 2D grating couplers in a photonic BiCMOS technology
    (Bristol : IOP Publ., 2020) Georgieva, Galina; Voigt, Karsten; Mai, Christian; Seiler, Pascal M.; Petermann, Klaus; Zimmermann, Lars
    We investigate numerically and experimentally sheared 2D grating couplers in a photonic BiCMOS technology with a focus on their splitting behavior. Two realization forms of a waveguide-To-grating shear angle are considered. The cross-polarization used as a figure-of-merit is shown to be strongly dependent on the grating perturbation strength and is a crucial limitation not only for the grating splitting performance, but also for its coupling efficiency. © 2020 The Japan Society of Applied Physics.