Quantum Coherence Lab

Zumbühl Group


News from our Group

On arXiv: Isotropic and Anisotropic g-factor Corrections in GaAs Quantum Dots

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)

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On arXiv: Quantum measurement induced a many-body transition

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)

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On arXiv: Deep Reinforcement Learning for Efficient Measurement of Quantum Devices

Deep reinforcement learning is an emerging machine learning approach which can teach a computer to learn from actions and rewards similar to the way humans learn from experience. Here, we use this approach for fully automatic identification of double dot bias triangles in a surface gated GaAs device. Oxford - Basel Collaboration lead by Natalia Ares (Oxford).
Nguyen et al., arXiv:2009.14825 (Sep 30, 2020)

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Published in New Journal of Physics: Fine-tuning with unsuperv. embedding learning

We 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. New Journal of Physics 22, 095003 (Sept 22, 2020)

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Group Hike to Wissigstock 2'887m

Shot of the brave thirteen who took it upon themselves to hike all the way to the top of Wissigstock at 2'887 meters altitude... refreshed and slightly proud... enjoying the breathtaking view from up there!

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