University of Basel

Department
of Physics

Quantum Coherence Lab - Zumbühl Group

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Published in Phys. Rev. Lett.: Edge-State Wave Functions from Momentum-Conserving Tunneling Spectroscopy

We employ the lowest 5 modes of a quantum wire to probe adjacent edge-states in momentum conserving tunneling spectroscopy. Combined with numerical Schrödinger-Poisson simulations this is a powerful technique to probe edge-state wave…
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Fully automatic tuning of a quantum device faster than human experts, Nature Comms

Robots taking over the quantum transport lab: In an up to 8D space, our machine learning algorithm tunes the device typically in under 70 minutes, surpassing our best human benchmark (although both human and machine performance can be…
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On arXiv: Silicon quantum dot devices with a self-aligned 2nd gate layer

We present silicon finFET quantum dots with perfectly self-aligned 2nd gate layer and gate lengths down to 15 nm. In a double quantum dot, we find Pauli spin blockade with leakage dominated by spin-orbit interaction and extract a hole…
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On arXiv: Strong spin-orbit interaction and g-factor renormalization of Ge/Si nanowire hole spins

We report a remarkably strong spin-orbit interaction, with spin-orbit length of 65 nm, comparable to the quantum dot size. Combined with a large orbital effect of the B-field, the strong spin-orbit interaction causes a significant…
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Pascal Würsch presents MSc Thesis

Pascal Würsch successfully completed his MSc thesis "Large Quantum Dots for Microkelvin Universal Coulomb Blockade Thermometry in Semiconductors" and presented his results to the group today on zoom. Formally, an ETH Zürich MSc thesis with…
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PhD Defense of Florian Froning

Florian Froning successfully defended his PhD thesis "Hole Spin Qubits in Ge/Si Core/Shell Nanowires" on zoom, with Prof. Georgios Katsaros, Institute of Science and Technology, Vienna, Austria, and Prof. Menno Veldhorst, Delft University…
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Fast Charge Readout with an Ultra-Low-Noise SQUID Amplifier: Published in Journal of Applied Physics!

Spin quantum computers will require fast and accurate qubit read out. Here, we use reflectometry with a SQUID preamplifier at 200 MHz to obtain record capacitance sensitivity of 0.07 aF/sqrt(Hz). Integrating for 1 μs, a signal-to-noise…
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On arXiv: Ultrafast Hole Spin Qubit with Gate-Tunable Spin-Orbit Switch

We demonstrate an ultrafast qubit with Ge/Si core/shell hole spins, with spin-flipping times as short as ~1 ns - a new record for a single-spin qubit. Next, we show a large degree of electrical control over the Rabi frequency, Zeeman…
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Review on Cooling Nanoelectronic Devices Published!

Review "Progress in Cooling Nanoelectronic Devices to Ultra‑Low Temperatures" from Lancaster and our group published in Journal of Low Temperature Physics! doi.org/10.1007/s10909-020-02472-9
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Rafael Eggli has joined the group to work on project thesis

Rafael Eggli (Nanoscience BSc, Basel) joined the group this week to work on his project thesis. He is working on FinFET Quantum dot devices in collaboration with Andreas Kuhlmann. Welcome to the Group, and looking forward to work with you!
MeinArbeitsplatz

Our Lab has been featured in UniNova

The article revolves around a typical work flow in our Cryolab including the transfer of Helium and the control of the measurement.
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Published in Nano Letters: Remote Doping of Scalable Nanowire Branches

Selective-area epitaxy provides a path toward high crystal quality, scalable and complex nanowire networks. Here, we demonstrate remote-doping in InGaAs nanowire networks and find weak anti-localization—a signature of strong spin–orbit…
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On arXiv: Out-of-plane corrugations in graphene based van der Waals heterostructures

2D materials are often envisioned as flat monoatomic truly 2D layers. However, out-of-plane corrugations are inevitably present. In an in-plane magnetic field, the ripples lead to random, inhomogeneous perpendicular fields, causing…
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Luca Forrer defends MSc thesis

Luca Forrer successfully completed his MSc thesis "Quantum Transport in Templated Indium Arsenide Nanowires" and defended his results in the group (on zoom). In this collaboration with Prof. Anna Fontcuberta i Morral’s group, the InAs wires…
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On arXiv: Edge State Wave Functions from Tunneling Spectroscopy

We use the lowest five modes of a quantum wire to probe adjacent quantum Hall edge state in tunneling spectroscopy. We self-consistently solve the Poisson-Schrödinger equations to simulate the spectroscopy, reproducing the experiment in…
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