Quantum Coherence Lab

Zumbühl Group


News from our Group

Single, double, and triple quantum dots in Ge/Si nanowires: new arXiv submission

We report highly tunable control of holes in Ge/Si core/shell nanowires (NWs). We demonstratethe a bility to create single quantum dots (QDs) of various sizes, with low hole occupation numbers and clearly observable excited states. For the smallest dot size we observe indications of single-hole occupation. In the double quantum dot con guration we observe Pauli spin blockade (PSB). These results open the way towards hole spin qubits. arXiv:1805.02532

Read more

Two new manuscripts on arXiv, on Quantum-Dot Orbital-Spectroscopy with In-Plane Magnetic Fields!

Semiconductor spin qubits are leading candidates for quantum computation. Despite impressive progress over two decades, a tool to characterize the orbitals hosting the spin is lacking. Here, we demonstrate a spectroscopy method for quasi-2D dots. Using magnetic fields with various strengths and orientations in the 2D plane, we extract the full 3D shape and orientation of the quantum orbitals of a single spin with sub-nm precision. The shorter paper, arXiv:1804.00162, demonstrates how the spectroscopy is performed in an experiment and how the orbitals can be determined. The longer submission, arXiv:1804:00128, contains the in-depth theoretical analysis of the principles which are at the heart of the new method.

Read more

Just accepted in Nano Letters: "Template-assisted scalable nanowire networks"

Topological qubits based on Majorana fermions have the potential to revolutionize the emerging field of quantum computing by making information processing significantly more robust to decoherence. In this Letter, we report gold-free templated growth of III-V NWs by molecular beam epitaxy using an approach that enables patternable and highly regular branched NW arrays on a far greater scale than what has been reported thus far. Our approach relies on the lattice-mismatched growth of InAs on top of defect-free GaAs nanomembranes (NMs) yielding laterally-oriented, low-defect InAs and InGaAs NWs.
Nano Letters DOI:

Read more

Master/Project thesis position available! Hands on a Spin Qubit Device: g-factor anisotropy in GaAs

We are looking for a motivated, talented and technology-savvy physics or nanoscience student for research of the theoretically predicted g-factor anisotropy in a lateral Gallium Arsenide (GaAs) quantum dot spin qubit device measured at sub-Kelvin temperature.

Read more

European Microkelvin Platform in Nature Materials Reviews

The growing demands of quantum materials, engineering and technology make access to microkelvin temperatures ever more essential. Experience in Europe suggests that new working methods, encouraged by an imaginative funding atmosphere, can accelerate progress in this frontier field. Review by George Pickett and Christian Enss in Nature Materials.

Read more