Low temperature record published in APL as an Editor's pick, with Scilight!Image: A Coulomb blockade thermometer on a nuclear demagnetization stage.

Low temperature record published in APL as an Editor's pick, with Scilight!Image: A Coulomb blockade thermometer on a nuclear demagnetization stage.

Hyperfine-phonon spin relaxation paper appeared on arXiv, reporting spin lifetimes of up to one minute in a GaAs single electron quantum dot

Welcome the new Bluefors XLD dry fridge to the team!

The Quantum Coherence Lab has a new Homepage!

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Yemliha "Bilal" Kalyoncu successfully defended his PhD thesis "Hydrogen Plasma Etched Graphene Nanoribbons" today with Dr. Jonathan Prance, Lancaster University, as coreferee and Prof. Ilaria Zardo chairing. Congratulations, Bilal, on a very nice thesis and exam, and thanks very much for all the work!

Having received his MSc in Physics from the University of Basel on the thermal conductivity of nanowires using Raman

thermometry in Prof. Ilaria Zardo's group, Miguel is starting his PhD thesis on the Ge/Si nanowire project, developing these as a platform for spin qubits and exotic quantum matter such as Majorana fermions. Welcome to the group, looking forward to work with you!

We derive a closed-form expression for the weak localization corrections to the magnetoconductivity of a 2D electron system with arbitrary Rashba and both linear and cubic Dresselhaus spin-orbit interactions in a perpendicular magnetic field geometry. In a reference frame with an in-plane z-axis along the spin-helix symmetry direction, we find a general decoupling algorithm for the Cooperon spin modes that leads to a representation invariant, closed-form expression. The anisotropy of the effective spin relaxation rates is fundamental to understanding spin-orbit coupling in quantum transport. Marinescu et al. arXiv:1811.04488

Tuning quantum devices is becoming time-consuming as systems are scaled up, e.g. to numerous gates or contacts, and will soon become intractable without automation. Here, we present measurements on a quantum dot done by a machine learning algorithm. This selects the most informative measurements to perform next using information theory and a probabilistic deep-generative model capable of generating multiple full-resolution reconstructions from scattered partial measurements. We demonstrate that the algorithm outperforms standard grid scan techniques, reducing the measurement time by a factor of ~4, thus laying the foundation for automated control of large quantum circuits. Lennon et al., arxiv.org/abs/1810.10042

Ambipolar quantum dots in silicon fin field-effect 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).

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.

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.

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).

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

We integrate ambipolar quantum dots in silicon fin field-effect transistors using exclusively standard complementary metal-oxide-semiconductor fabrication techniques. We realize ambipolarity by using a metallic nickel silicide with Fermi level close to the silicon mid-gap position. 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. arXiv:1807.04121

**Research** focuses on quantum transport experiments investigating quantum coherence, electron spins and nuclear spins and interactions in semiconductor and graphene nanostructures. Ongoing projects include

- spin qubits in coupled, laterally gated GaAs quantum dots
- microkelvin temperatures in nanoscale sample
- novel quantum states of matter, such as electron or nuclear spin helices, topological states and Majorana fermions
- spin-orbit coupling in GaAs quantum wells
- experiments investigating mesoscopic electron transport, including graphene nanoribbon research

We are interested in coherent manipulation of individual quantum systems in solid state nanostructures with quantum computation as a long term goal.

**Experiments** investigate quantum transport through semiconductor nanostructures which are fabricated in house using high mobility 2D electron gas materials obtained from collaborating molecular beam epitaxy labs. Experiments are typically performed in dilution refrigerators at millikelvin temperatures in magnetic fields. Measurements are done using electronic low-noise techniques and may involve nanosecond-pulsing and microsecond readout schemes.

An ERC Starting Grant from the first ERC call was awarded to our group and boosted our research from 2008-2013 (press release)

Positions are currently available, please see the positions page.

We are affiliated with

- Department of Physics, University of Basel
- Swiss Nanoscience Institute (SNI)
- Basel QC2 Center for Quantum Computing and Quantum Coherence
- Harvard Nanoscale Science and Engineering Center (NSEC) of the US National Science Foundation and
- NCCR Quantum Science and Technology - NCCR QSIT of the Swiss NSF. QSIT video

Our group enjoys numerous ongoing collaborations, including the following groups (in arbitrary order)

- Schönenberger group, Basel (nano-electronics, fabrication)
- Loss group, Basel (theory)
- Gossard group at UC Santa Barbara (MBE growth)
- Wegscheider group, ETH Zurich (MBE growth)
- Pfeiffer group, Princeton University (MBE growth)
- Yacoby group, Harvard University (GaAs quantum wires)
- Awschalom group, University of Chicago (persistent spin helix and spin-orbit coupling in GaAs quantum wells)
- Egues group, Sao Paulo University (theory)
- Pekola group, Aalto University, Helsinki (Coulomb blockade thermometry)
- Lancaster group (George Pickett), England (nuclear refrigeration)
- European microkelvin collaboration, ultra-low temperature physics and techniques (EU FP7 integrating activity)
- BaselCryogenics, Low temperature filtering and thermalization

23 Aug 13:15

1.09

Master Thesis Defense - Fabian

20 Sep 13:15

1.09

Master Thesis Defense - Simon Svab

11 Okt 13:15

1.09

Tim

18 Okt 13:15

1.09

Andreas

thermometry in Prof. Ilaria Zardo's group, Miguel is starting his PhD thesis on the Ge/Si nanowire project, developing these as a platform for spin qubits and exotic quantum matter such as Majorana fermions. Welcome to the group, looking forward to work with you!

**Research** focuses on quantum transport experiments investigating quantum coherence, electron spins and nuclear spins and interactions in semiconductor and graphene nanostructures. Ongoing projects include

- spin qubits in coupled, laterally gated GaAs quantum dots
- microkelvin temperatures in nanoscale sample
- novel quantum states of matter, such as electron or nuclear spin helices, topological states and Majorana fermions
- spin-orbit coupling in GaAs quantum wells
- experiments investigating mesoscopic electron transport, including graphene nanoribbon research

We are interested in coherent manipulation of individual quantum systems in solid state nanostructures with quantum computation as a long term goal.

**Experiments** investigate quantum transport through semiconductor nanostructures which are fabricated in house using high mobility 2D electron gas materials obtained from collaborating molecular beam epitaxy labs. Experiments are typically performed in dilution refrigerators at millikelvin temperatures in magnetic fields. Measurements are done using electronic low-noise techniques and may involve nanosecond-pulsing and microsecond readout schemes.

An ERC Starting Grant from the first ERC call was awarded to our group and boosted our research from 2008-2013 (press release)

Positions are currently available, please see the positions page.

We are affiliated with

- Department of Physics, University of Basel
- Swiss Nanoscience Institute (SNI)
- Basel QC2 Center for Quantum Computing and Quantum Coherence
- Harvard Nanoscale Science and Engineering Center (NSEC) of the US National Science Foundation and
- NCCR Quantum Science and Technology - NCCR QSIT of the Swiss NSF. QSIT video

Our group enjoys numerous ongoing collaborations, including the following groups (in arbitrary order)

- Schönenberger group, Basel (nano-electronics, fabrication)
- Loss group, Basel (theory)
- Gossard group at UC Santa Barbara (MBE growth)
- Wegscheider group, ETH Zurich (MBE growth)
- Pfeiffer group, Princeton University (MBE growth)
- Yacoby group, Harvard University (GaAs quantum wires)
- Awschalom group, University of Chicago (persistent spin helix and spin-orbit coupling in GaAs quantum wells)
- Egues group, Sao Paulo University (theory)
- Pekola group, Aalto University, Helsinki (Coulomb blockade thermometry)
- Lancaster group (George Pickett), England (nuclear refrigeration)
- European microkelvin collaboration, ultra-low temperature physics and techniques (EU FP7 integrating activity)
- BaselCryogenics, Low temperature filtering and thermalization

23 Aug 13:15

1.09

Master Thesis Defense - Fabian

20 Sep 13:15

1.09

Master Thesis Defense - Simon Svab

11 Okt 13:15

1.09

Tim

18 Okt 13:15

1.09

Andreas