Quantum Coherence Lab

Zumbühl Group


News from our Group

On arXiv: Progress in cooling nanoelectronic devices to ultra-low temperatures

A number of groups worldwide are working to produce sub-millikelvin on-chip electron temperatures, motivated by the possibility to observe new physics and improving quantum device performance. In this review, we focus on on-chip demagnetisation refrigeration, which was used by multiple groups to reach temperatures around 1mK, with a current record below 0.5 mK. https://arxiv.org/abs/2001.07419


On arXiv: Quantum device fine-tuning using unsupervised embedding learning

We experimentally demonstrate an algorithm capable of fi ne-tuning several device parameters at once. The algorithm acquires a measurement, scores it using a variational auto-encoder, and optimizes gate voltage via the score in real-time in an unsupervised fashion. https://arxiv.org/abs/2001.04409


Published in PRB: Symmetry breaking of the persistent spin helix in quantum transport

We introduce a new spin quantization axis via the persistent spin helix, revealing a full decoupling of the Cooperon triplet scattering modes as well as decoupled Landau levels. This makes it possible to derive a closed-form expression for the weak localization magnetoconductivity, thus providing a new paradigm of localization in the weakly-broken spin symmetry regime.
Weigele et al., PRB101, 035414 (Jan 16, 2020).


Asser Elsayed, Imec Leuven, starts EMP access on Si and GeSi Qubit materials

Asser Elsayed from the group of Dr. Iuliana Radu and Dr. Bogdan Govoreanu, Imec Leuven, Belgium, is starting a user access project on the Basel node of the European Microkelvin Platform (EMP). The project is working to develop Si and GeSi materials for spin qubit applications.


New on the arXiv: Machine learning automatic tuning of a quantum dot

We demonstrate a statistical tuning algorithm that navigates the entire large parameter space of a gate-defined quantum dot. Using just a few modelling assumptions, we demonstrate fully automated tuning to the double dot regime.This also makes possible to give a quantitative measurement of device variability, from device to device, and also after thermal cycles. https://arxiv.org/abs/2001.02589