Quantum Coherence Lab

Zumbühl Group

 

News from our Group

"Ambipolar dots in Si finFETs..." published in Appl. Phys. Letters

Ambipolar quantum dots in silicon fin fi eld-eff ect transistors are defined using exclusively standard complementary metal-oxide-semiconductor fabrication techniques. We demonstrate stable quantum dot operation in the few charge carrier Coulomb blockade regime for both electrons and holes, opening the way for spin qubits hosted in such fin transistors. Appl. Phys. Lett. 113, 122107 (Sep 21, 2018).

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"Evolution of the Quantum Hall bulk spectrum" published in Nature Communications!

Using a GaAs cleaved-edge quantum wire, we perform spectroscopy revealing the momentum and position of the quantum Hall edge states with unprecedented precision. We present models in excellent agreement with the experiment—thus providing direct evidence for the bulk to edge correspondence. In addition, we observe Fermi level pinning, exchange-enhanced spin splitting and signatures of edge-state reconstruction. Published on Sept. 12 in Nature Communications, accompanied by an Uni News and a tweet.

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"Hyperfine-phonon spin relaxation" published in Nature Communications!

Understanding and control of the spin relaxation time T1 is a key challenge for spin qubits, setting the fundamental upper limit to the qubit coherence and readout fidelity. We establish the prediction of hyperfine-phonon spin relaxation experimentally, by measuring T1 over an unprecedented range of magnetic fields and report a maximum T1=57±15 s at the lowest fields, setting a new record for the spin lifetime in a nanostructure. Published on Aug 27 in Nature Communiations, with UniNews media release.

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Pulished in Appl. Phys. Letters: Ge/Si quantum dots

Published online on Aug 15 in Applied Physics Letters, our paper on gate defined quantum dots in Ge/Si nanowires, with single, double and triple dots, Pauli spin blockade, and signatures of a single hole quantum dot. Appl. Phys. Lett. 113, 073102 (2018).

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Spin-orbit and g-factor effects in gate define quantum dots

We analyze orbital effects of an in-plane magnetic field on the spin structure of states of a gated quantum dot. Starting with a k.p Hamiltonian, we perturbatively calculate these effects for the conduction band of GaAs. We quantify several corrections to the g-tensor and reveal their relative importance and find numerous terms. The Rashba, Dresselhaus and isotropic terms give the largest contributions in magnitude, up to 5% or 10% of the bulk value at zero field. Stano et al., arXiv:1808.03963

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