Fon-Times Interview mit Dominik Zumbühl. Seit rund zwanzig Jahren läuft die zweite Revolution der Quantenphysik. Neue Experimente führen vor Augen, dass sie die verrückte Welt der Quantenphysik genutzt werden kann, um nützliche Dinge anzustellen. “Heute haben wir die Chance, die Grundlagen für ein neues Silicon Valley zu legen.” Fon-Times Artikel, pdf
Even when sandwiched between atomically flat hBN crystals, surprisingly, graphene still exhibits ripples, even in absence of bubbles. These out-of-plane corrugations reduce mobility and suppress weak localization in an in-plane magnetic field. This effect allows extraction of the corrugation volume, in very good agreement with AFM measurements.
Basel - Budapest - Tsukuba as well as Schönenberger - Zumbühl collaboration!
Zihlmann, Makk et al. Phys. Rev. B102, 195404 (Nov 4, 2020)
Molecular hydrogen can block liquid He (LHe) intake capillaries typically used on 1K pots of many cryostats, causing severe disruption to the experiments. Here, we measure molecular hydrogen content in the liquifier helium gas supply and present measures to decrease hydrogen content in LHe: (i) better He supply quality (ii) release of dirt gas during liquifier purge cycles and (iii) installation of two catalytic converters to absorb the hydrogen. These actions have eliminated our low-temperature impedance blockage occurrences now for more than two years.
Sifrig et al., arXiv:2010:14136 (Oct 27, 2020)
The spin splitting defines the qubit energy and is one of the fundamental properties of a semiconductor electron in a magnetic field. Here, we measure and separate the isotropic and anisotropic corrections to the bulk g-factor in two GaAs spin qubit devices, finding good agreement with recent theory. This also has implications for GaAs spin qubits, recently enjoying a revival due to mitigation of hyperfine decoherence by active stabilization. Collaboration between Basel (exp.& th.), RIKEN (theory) and UCSB (2DEG).
Camenzind, Svab et al., arXiv:2010.11185 (Oct 21, 2020)
The act of measurement in quantum mechanics is still mysterious and not microscopically understood. In our work, we show that even a weak (non-projective) measurement of a quantum dot system with an adjacent detector can result in a fundamental change of the occupied state, involving also the state’s many-body environment. Collaboration with Oded Zilberberg and Group (ETHZ), Bernd Braunecker (St. Andrews) and Clemens Müller (IBM Zürich).
Ferguson, Camenzind et al., arXiv:2010.04635 (Oct 9, 2020)