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Quantum Coherence in Nanoscale Systems

English title Quantum Coherence in Nanoscale Systems
Applicant Zumbühl Dominik
Number 157213
Funding scheme Project funding (Div. I-III)
Research institution Departement Physik Universität Basel
Institution of higher education University of Basel - BS
Main discipline Condensed Matter Physics
Start/End 01.10.2014 - 31.03.2018
Approved amount 600'000.00
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Keywords (8)

electron spin and GaAs nuclear spin; nuclear magnetism; electron interactions; quantum coherence; persistent spin helix; mesoscopic physics; nanoscience; experimental condensed matter physics

Lay Summary (German)

Lead
Die Quantenphysik wurde vor über hundert Jahren entdeckt und erstmals entwickelt, allerdings ist es erst in jüngster Zeit, dass wir das Werkzeug und auch die Materialien in Händen halten um Quantensysteme im Labor zu untersuchen, zu verstehen, und kontrolliert zu manipulieren. Dies öffnet uns die Türen zur fundamentalen Studie der Gesetze der Quantenmechanik, z. B. in nanoelektronischen Proben, und legt das Fundament für zukünftige Quantentechnologien wie Quantencomputing und neue Quantenmaterialien. Die experimentelle Realisierung neuer Quantenzustände in nanoskopischen Systemen - mit dem Potenzial zukünftig als Qubits zu fungieren - und die Erforschung der zugrundeliegenden Physik gehört zu den spannendsten und aktivsten Forschungsgebieten der modernen Festkörperphysik.
Lay summary

Vor kurzem haben unsere Experimente erste klare Hinweise auf helikale Kernspinordnung in GaAs Quantendrähten ergeben. Hier wollen wir mittels Tunnelspektroskopie am Doppeldraht mehr Licht in dieses System zu bringen, mit dem Ziel die Natur dieses Zustands zu verstehen. Tunnelspektroskopie kann zur Messung der elektronischen Dispersion verwendet werden, welche nach theoretischen Voraussagen im Zustand der Kernspin-Helix eine spinselektive Lücke bei der Fermienergie für die Hälfte der Moden aufweist. Zudem arbeitet die Gruppe Wegscheider (ETH Zürich) am Wachstum neuer Quantendrähte, und ebnet damit den Weg zu einer neuen Generation von Experimenten in der verschiedene vorher nicht zugängliche Parameter variiert werden können (Draht Länge, Einzel- oder Doppeldraht etc).

Die Spin-Bahn-Kopplung ist  der dominante Mechanismus in der Physik der Spins in Halbleitern und spielt deshalb eine ausschlagebende Rolle in Spintronik und Quantencomputing. Kürzlich haben wir hervorragende Kontrolle über die Spin-Bahn-Parameter in GaAs Quantenheterostrukturen durch Verwendung von Strukturen mit Top- und Backgates demonstriert. Nun werden wir diese Methode auf Nanostrukturen und Nanodrähte  anwenden, in Zusammenarbeit mit der Gruppe Fontcuberta (EPFL). In Quantenpunkten ermöglicht die elektrische Kontrolle der Spin-Bahn-Kopplung eine neue Herangehensweise zur Spinphysik, die das Wechselspiel von Spin-Bahn-Wechselwirkung und nuklearer Hyperfeinkopplung einbindet. Weiterhin sind Systeme mit viel stärkerer Spin-Bahn-Wechselwirkung als GaAs von grossem Interesse für helikale und topologische Materiezustände inklusive Majorana Fermionen.

Wir beteiligen uns aktiv an den Aktivitäten des Swiss Nanoscience Institute am Department PhysiK der Universität Basel, dem NCCR Quantum Science and Technology (Zurich/Basel), und dem Basel Center for Quantum Computing and Quantum Coherence.

Für weitere Informationen besuchen Sie bitte http://ZumbuhlLab.unibas.ch.

Direct link to Lay Summary Last update: 23.03.2017

Responsible applicant and co-applicants

Employees

Publications

Publication
Template-Assisted Scalable Nanowire Networks
Friedl Martin, Cerveny Kris, Weigele Pirmin, Tütüncüoglu Gozde, Martí-Sánchez Sara, Huang Chunyi, Patlatiuk Taras, Potts Heidi, Sun Zhiyuan, Hill Megan O., Güniat Lucas, Kim Wonjong, Zamani Mahdi, Dubrovskii Vladimir G., Arbiol Jordi, Lauhon Lincoln J., Zumbühl Dominik M., Fontcuberta i Morral Anna (2018), Template-Assisted Scalable Nanowire Networks, in Nano Letters, 18(4), 2666-2671.
On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK
Palma M., Scheller C. P., Maradan D., Feshchenko A. V., Meschke M., Zumbühl D. M. (2017), On-and-off chip cooling of a Coulomb blockade thermometer down to 2.8 mK, in Applied Physics Letters, 111(25), 253105-253105.
Anisotropic etching of graphite and graphene in a remote hydrogen plasma
Hug D., Zihlmann S., Rehmann M. K., Kalyoncu Y. B., Camenzind T. N., Marot L., Watanabe K., Taniguchi T., Zumbühl D. M. (2017), Anisotropic etching of graphite and graphene in a remote hydrogen plasma, in npj 2D Materials and Applications, 1(1), 21-21.
Stretchable Persistent Spin Helices in GaAs Quantum Wells
Dettwiler Florian, Fu Jiyong, Mack Shawn, Weigele Pirmin J., Egues J. Carlos, Awschalom David D., Zumbühl Dominik M. (2017), Stretchable Persistent Spin Helices in GaAs Quantum Wells, in Physical Review X, 7(3), 031010-031010.
Magnetic cooling for microkelvin nanoelectronics on a cryofree platform
Palma M., Maradan D., Casparis L., Liu T.-M., Froning F. N. M., Zumbühl D. M. (2017), Magnetic cooling for microkelvin nanoelectronics on a cryofree platform, in Review of Scientific Instruments, 88(4), 043902-043902.

Collaboration

Group / person Country
Types of collaboration
Prof. Dr. Werner Wegscheider, ETH Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Dr. Loren Pfeiffer, Princeton United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
European Microkelvin Collaboration Finland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Dr. Art Gossard, University of California, Santa Barbara United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Daniel Loss, Basel Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
NCCR Quantum Science and Techology QSIT Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Prof. Dr. David Awschalom, University of Chicago United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
NSEC Network, based at Harvard University United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Anna Fontcuberta, EPF Lausanne Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Prof. Dr. Amir Yacoby, Harvard University United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Jose Carlos Egues, University of Sao Paulo, Brazil Brazil (South America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Christoph Bruder, Basel Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Dr. Christian Schönenberger, Basel Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Physics Colloquium Talk given at a conference Spins and Orbits in Semiconductor Nanostructures 20.04.2018 Sao Carlos, Brazil Zumbühl Dominik;
APS March meeting Talk given at a conference Stretching and Breaking the Persistent Spin Helix 05.03.2018 Los Angeles, United States of America Zumbühl Dominik;
Spin-Qubit 3, 3rd Conference and Workshop on Spin-based Quantum Information Processing Talk given at a conference Hyperfine-phonon spin relaxation in a single-electron GaAs quantum dot 06.11.2017 Sydney, Australia Zumbühl Dominik;
Quantum States in Atoms and Molecules at Surfaces, international workshop Talk given at a conference Controlling Charge and Spin of a Single Electron 10.09.2017 Monte Verita, Switzerland Zumbühl Dominik;
Quantum Spintronics at Interfaces Talk given at a conference Edge States Spectroscopy with a GaAs Quantum Wire 04.09.2017 San Sebastian, Spain Zumbühl Dominik;
International Conference on Ultra Low Temperature Physics Talk given at a conference Magnetic Cooling for Nanoelectronics below 10 mK 18.08.2017 Heidelberg, Germany Zumbühl Dominik;
18th Brazilian Workshop on Semiconductor Physics Talk given at a conference Hyperne and Spin-Orbit Spin Relaxation in a GaAs Single Electron Quantum Dot 14.08.2017 Sao Paulo, Brazil Zumbühl Dominik;
International workshop on Spin-Orbit Materials Talk given at a conference Spin-Orbit and Hyperne Coupling in GaAs 2D and 0D Systems 14.07.2017 Luxembourg, Luxembourg Zumbühl Dominik;
workshop on collective spin transport in electrical insulators Talk given at a conference Spin-Orbit and Hyperne Coupling in GaAs 2D and 0D Systems 01.05.2017 Natal, Brazil Zumbühl Dominik;


Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions Der Quantencomputer - Superrechner der Zukunft? Western Switzerland 2018
Talks/events/exhibitions Der Quantencomputer: Superrechner der Zukunft + Lab tour Western Switzerland 2018
Talks/events/exhibitions Nanoelektronik für den Quantencomputer Western Switzerland 2018
Talks/events/exhibitions Der Quantencomputer: Superrechner der Zukunft Western Switzerland 2017
Talks/events/exhibitions Entanglements of Matter and Disciplines International 2017
Talks/events/exhibitions Open Lab 2017/II (Unibas intro to BS/BL parliamentarians) German-speaking Switzerland 2017
Talks/events/exhibitions Site visit of World Economic Forum Delegation at the Department of Physics International 2017
Talks/events/exhibitions Treffen mit Bundesrat Schneider-Amman und Rektorin Schenker-Wiki Western Switzerland German-speaking Switzerland 2017

Associated projects

Number Title Start Funding scheme
138217 Quantum Coherence in Nanoscale Systems 01.10.2011 Project funding (Div. I-III)
179024 Quantum Coherence in Nanoscale Systems 01.04.2018 Project funding (Div. I-III)

Abstract

This proposal consists of three projects, outlined below: helical electron and nuclear spin order, spin-orbit coupling in low-dimensional systems, and fundamental processes in quantum dots.We have recently published first evidence for helical nuclear spin order in GaAs cleaved edge overgrowth wires -- a successful outcome of the predecessor of this proposal. But this was only the first step, many questions are open. Here, we propose to use double-wire tunneling spectroscopy, finite-size interference fringes and thermo-power experiments (among others) to shead independent, additional light on the this system.Tunneling spectroscopy can extract the electronic dispersion, which is predicted to reflect the nuclear helix: a spin-selective gap at the Fermi energy in half of the modes. Further, in collaboration with the Wegscheider group (ETH Zurich), we will grow new wires. This is a very challenging task, but with a large pay-off, giving access also to single wires, multi mode systems and side gates -- all very useful.The spin-orbit (SO) interaction is the preeminent mechanism governing the physics of spins in semiconductors and thus plays a crucial role in spintronics and quantum computation. Recently, we have demonstrated unprecedented command over the SO parameters in GaAs quantum wells -- another successful outcome of the predecessor proposal. Now, we propose to apply this technique to confined geometries in nanostructures, where control of the SO interaction is essential. In quantum dots, SO control gives access to longer spin relaxation times, allows investigation of an unresolved decoherence problem, and gives a much better approach to study the physics of the singlet-triplet avoided crossing in two electron dots.For this, the GaAs quantum well material might have to be improved in terms of mobility and charge stability. Further, systems with much stronger SO coupling than GaAs are also of great interest for helical and topological states of matter including Majorana fermions and parafermions. Here, we propose to investigate InAs structures in both 2D and 1D, working closely with the Fontcuberta group (EPF Lausanne) and Wegscheider group (ETH Zurich).Finally, we propose to study a number of fundamental processes in quantum dots: a thermally activated charge instability, causing both spin and charge relaxation, the interplay between the spin-orbit and hyperfine interaction, the spin tunneling asymmetry, and the spin relaxation process, including its magnetic field asymmetry. In dots with in-situ controllable spin-orbit coupling, the spin relaxation rate can be extended considerably.If GaAs quantum dots are going to be used as the elementary building blocks for future quantum information processing, then it is crucial that these fundamental effects are well understood and under check, since they can severely limit operation, particularly when scaling to a larger number of quibts.
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