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Quantum Coherence in Nanoscale Systems

English title Quantum Coherence in Nanoscale Systems
Applicant Zumbühl Dominik
Number 121905
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 01.10.2008 - 30.09.2011
Approved amount 724'818.00
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Keywords (10)

quantum coherence; electron spin and GaAs nuclear spin; coherent manipulation of quantum states; quantum computation; electron interactions; experimental condensed matter physics; nanoscience; mesoscopic physics; electron and GaAs nuclear spin physics;

Lay Summary (English)

Lead
Lay summary
This project consists of two related topics:1. electron spins in coupled quantum dots, working towards implementation of quantum computation schemes 2. fundamental mesoscopic transport phenomena probing electron interactions, coherence and spin in 2D systems and quantum dots.Quantum coherence in nanoscale systems enables study of fundamental physics in condensed matter systems and has promising applications for quantum information processing. Experimental realization of proposed qubits in the solid state and investigation of the underlying physics controlling coherence is at the forefront of modern condensed matter physics. The electron spin qubit in coupled quantum dots is currently among the most promising approaches to quantum computing. Despite impressive recent experimental progress in spin manipulation, spin coherence is currently significantly impeded by nuclear spin fluctuations. The experiments proposed here aim to tackle this coherence challenge. We intend to investigate the nuclear hyperfine physics and dynamics using spin Blockade, creating nuclear polarizations and aim to strongly enhance spin coherence. As spin relaxation always fundamentally limits coherence, we intend to further study the low field and field anisotropy properties of spin relaxation.Quantum coherence, electron spins and electron interactions were and remain very much at the center of mesoscopic physics. We propose to tackle new aspects of these recurring themes by investigating a two impurity Kondo effect and a related quantum phase transition in a two-electron double quantum dot. Electron interactions and coherence also are manifest in the many-body physics of 2D systems, mesoscopic Fermi edge resonances and magnetic field asymmetries of finite bias conductance through open quantum dots. Experiments will investigate quantum transport through semiconductor nanostructures which will be fabricated in-house with both optical- and electron beam lithography nanofabrication techniques using GaAs high-mobility 2D electron gas materials, grown in 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. We are affiliated with the NCCR Nanoscale Science center of the Swiss NSF (www.nccr-nano.org), the Basel Center for Quantum Computing and Quantum Coherence (www.qc2.unibas.ch) and the NSEC Harvard Nanoscale Science and Engineering Center (www.nsec.harvard.edu) of the US National Science Foundation.For more information, visit http://ZumbuhlLab.unibas.ch
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Metallic Coulomb Blockade Thermometry down to 10 mK and below
Casparis L., Maschke M., Maradan D., Clark A. C., Scheller C., Schwarzwaelder K. K., Pekola J. P., Zumbuhl D. M., Metallic Coulomb Blockade Thermometry down to 10 mK and below, in cond-mat, 1111(1972), 1-3.
Method for cooling nanostructures to microkelvin temperatures
Clark A. C., Schwarzwaelder K. K., Bandi T., Maradan D., Zumbuhl D. M., Method for cooling nanostructures to microkelvin temperatures, in Review of Scientific Instruments, 81, 103904-1-103904-4.
Spin-Dependent Tunneling of Single Electrons into an Empty Quantum Dot
Amasha S., MacLean K., Radu I. P., Zumbuhl D. M., Kastner M. A., Spin-Dependent Tunneling of Single Electrons into an Empty Quantum Dot, in Physical Review B, 78, 041306R-1-041306R-4.
The Nuclear Spin Environment in Lateral GaAs Spin Valves
Koelbl D., Zumbuhl D. M., Fuhrer A., Salis G., Alvarado S., The Nuclear Spin Environment in Lateral GaAs Spin Valves, in cond-mat, 1109(6332), 1-7.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
IOP Condensed Matter and Materials Physics Division Meeting 13.12.2011 Manchester, UK
QSIT Junior Meeting 05.06.2011 Passugg, CH
Invited seminar, University of Stuttgart, Germany 03.06.2011 Stuttgart, Germany
European Microkelvin Meeting 14.03.2011 Smolenice, Slovakia
Invited seminar, Max Planck Institute Stuttgart 01.02.2011 Stuttgart, Germany
First General Meeting of the NCCR Quantum Science and Technology 12.01.2011 Arosa, Switzerland
Deutsche Physikerinnentagung der DPG 23.11.2010 Saarbr¨ucken, Deutschland
Sao Paulo School of Advances Science: Spintronics and Quantum Computation 14.11.2010 Sao Carlos, Brazil
Microkelvin meeting, Kirchhoff Institut fur Physik 05.11.2010 Heidelberg, Germany
Microkelvin Network meeting 15.10.2010 Helsinki, Finnland


Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions Gymnaisum Leonhard, Basel, “Nanotechnologie fuer den Quantenrechner der Zukunft” German-speaking Switzerland 24.03.2011
Talks/events/exhibitions Lab Tour for Young Physicists Forum CH German-speaking Switzerland 11.11.2011
Talks/events/exhibitions Nanotechnologie fur den Quantenrechner der Zukunft German-speaking Switzerland 12.10.2011
Talks/events/exhibitions Freie Akademische Gesellschaft Basel, “Auf dem Weg zum Quantencomputer” German-speaking Switzerland 13.11.2010
Talks/events/exhibitions Lecture for Nano I Students German-speaking Switzerland 17.11.2010

Associated projects

Number Title Start Funding scheme
113776 Quantum Coherence in Nanoscale Systems 01.10.2006 Project funding (Div. I-III)
113776 Quantum Coherence in Nanoscale Systems 01.10.2006 Project funding (Div. I-III)
138217 Quantum Coherence in Nanoscale Systems 01.10.2011 Project funding (Div. I-III)
138217 Quantum Coherence in Nanoscale Systems 01.10.2011 Project funding (Div. I-III)

Abstract

Macroscopic control of coherent quantum states is a major theme in much of modern physics because quantum coherence enables study of fundamental physics and has promising applications for quantum information processing. The potential significance of quantum computing is by now widely recognized. This proposal consists of three projects: electron spin qubits in coupled quantum dots, topologically protected coherence in non-Abelian fractional quantum hall states and fundamental mesoscopic transport phenomena probing electron interactions, coherence and spin in quantum dots.The electron spin qubit in coupled quantum dots (project A) is currently among most promising quantum computing schemes. Despite impressive recent experimental progress in spin manipulation, spin coherence is currently significantly impeded by nuclear host-spin fluctuations. The experiments proposed here aim to tackle this coherence challenge. We intend to investigate the nuclear hyperfine physics and dynamics using spin Blockade and creating nuclear polarizations and aim to strongly enhance spin coherence with nuclear spin state narrowing techniques including spin resonance methods. As spin relaxation always fundamentally limits coherence, we intend to further study the low field and field anisotropy properties of spin relaxation.The prospect of physically realizing non-Abelian quantum states (project B) with topological properties is very exciting because no such quantum states have yet been discovered in nature, though the physics to be discovered would be truly unique and novel. Potential applications for topologically protected quantum computation further motivate experiments aimed at demonstrating non-Abelian statistics, which we propose to perform using quantum interference effects in certain even denominator fractional quantum Hall states.Quantum coherence, electron spin and electron interactions (project C) were and remain very much at the center of mesoscopic physics. We propose to tackle new aspects of these recurring themes by investigating a two impurity Kondo effect and a related quantum phase transition in a two electron double quantum dot. Electron interactions and coherence also are manifest in the many-body physics of mesoscopic Fermi edge resonances and magnetic field asymmetries of finite bias conductance through open quantum dots. The naturally unifying theme in this proposal is quantum coherence, which is central to mesoscopic physics in general as much as to quantum computation in particular.The main applicant is Prof. Dominik Zumbühl, an assistant professor who for the past 18 months has been initiating the Quantum Coherence Group and measurement lab at the Department of Physics, University of Basel. The lab setup has made excellent progress, and currently first experiments on Basel-fabricated few electron double dots with charge sensors are under way in a newly installed cryostat. Prof. Zumbühl has a strong background in mesoscopic and quantum dot physics and was educated in some of the worlds leading labs at Stanford, Harvard and MIT. Recently, Prof. Zumbühl was awarded one of the highly contested Starting Grants from the European Research Council (ERC). Together with our international collaborations with groups at Harvard, Alcatel-Lucent Bell-Labs, MIT and UCSB as well as Swiss and also in-house collaborations, we form an outstanding and internationally recognized team working together on these projects.We are affiliated with the NCCR Nanoscale Science center of the Swiss NSF (www.nccr-nano.org), the Basel Center for Quantum Computing and Quantum Coherence (www.qc2.unibas.ch) and the NSEC Harvard Nanoscale Science and Engineering Center (www.nsec.harvard.edu) of the US National Science Foundation.For more information, visit http://ZumbuhlLab.unibas.ch
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