Solid State Based Quantum Information Processing QIP 2006

Transcrição

International Workshop
on
Solid State Based
Quantum Information Processing
QIP 2006
May 24 – 26, 2006
Herrsching, Bavaria
.
c Walther-Meißner-Institut
Impressum
Herausgeber, Redaktion, Satz und Druck:
Walther-Meißner-Institut
Bayerische Akademie der Wissenschaften
Walther-Meißner Straße 8
D-85748 Garching
Tel.:
Fax:
web:
+49 – 89 289 14201
+49 – 89 289 14206
http://www.wmi.badw.de
International Workshop
on
Solid State Based
Quantum Information Processing
QIP 2006
Location
Educational Center of the Bavarian Agricultural Association
Rieder Straße 70
D-82211 Herrsching, Germany
phone: +49 – 8152 938 000
fax: +49 – 8215 938 224
web: www.HdbL-Herrsching.de
e-mail: [email protected]
Organizing Committee
Rudolf Gross, Bavarian Academy of Sciences, Munich, Germany
Achim Marx, Bavarian Academy of Sciences, Munich, Germany
Matthias Opel, Bavarian Academy of Sciences, Munich, Germany
Martin Brandt, Technical University of Munich, Germany
Sigmund Kohler, University of Augsburg, Germany
Florian Marquardt, Ludwig-Maximilians-University Munich, Germany
Program Committee
The Members of SFB 631
see www.wmi.badw-muenchen.de/SFB631
.
This workshop is supported by the Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 631 and the Bavarian Academy of Sciences.
Contents
Program
7
Oral Presentations
15
Abstracts: Invited Talks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
Abstracts: Contributed Talks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
Poster Presentations
47
Abstracts: Poster Presentations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
49
Notes
71
List of Participants
79
Author Index
89
Room Plans
91
5
Program
7
P ROGRAM
QIP 2006
Wednesday, May 24, 2006
12:00 – 13:30
Dining
Hall
Lunch
13:30 – 13:40
Hall 14
Workshop Opening
Superconducting Systems I
13:40 – 14:20
Hall 14
14:20 – 15:00
Hall 14
15:00 – 15:20
Hall 14
15:20 – 15:40
Hall 14
15:40 – 16.20
Foyer
Kees Harmans
Kavli Institute of NanoScience, Delft University of Technology ,
The Netherlands
Fux Qubits and Their Readout
Evgeni Il’ichev
Institute for Physical High Technology, Jena, Germany
Concept of Adiabatic Computation with Superconducting Flux
Qubits – First Experimental Results
Paul Müller
Physikalisches Institut III, Universität Erlangen-Nürnberg, Germany
Macroscopic Quantum Tunneling in Intrinsic Josephson Junctions
Frank Deppe
Walther-Meißner-Institut, Garching, Germany
Flux Qubit Readout via a Capacitive Bias
Coffee Break
Superconducting Systems II
16:20 – 17:00
Hall 14
17:00 – 17:30
Hall 14
Andreas Wallraff
Department of Physics, ETH Zurich, Switzerland
Circuit QED: Superconducting Qubits and Cavities
Matteo Mariantoni
Walther-Meißner-Institut, Garching, Germany
On-Chip Microwave Fock States and Quantum Homodyne Measurements
2006
9
QIP 2006
10
P ROGRAM
17:30 – 18:00
Hall 14
Florian Marquardt
CeNS and Arnold-Sommerfeld-Center for Theoretical Physics,
LMU Munich, Germany
Efficient On-chip Source of Microwave Photon Pairs
18:00
Dining
Hall
Dinner
19:00
SR1,
SR2
Poster Session
SFB 631
P ROGRAM
QIP 2006
Thursday, May 25, 2006
Theory I
08:30 – 09:10
Hall 14
09:10 – 09:50
Hall 14
09:50 – 10:20
Hall 14
10:20 – 10:50
Foyer
Ignacio Cirac
Max-Planck Institute for Quantum Optics, Garching,Germany
Quantum Simulations with Trapped Ions
Jonathan Baugh
Institute for Quantum Computing, University of Waterloo,
Canada
Solid-State Nuclear Magnetic Resonance-Based Quantum
Information Processing: What Can we Learn?
Jens Siewert
DMFCI, University of Catania, Italy
Entanglement of Mixed States with GHZ and W State
Components
Coffee Break
Quantum Optics meets Solid State I
10:50 – 11:30
Hall 14
11:30 – 12:10
Hall 14
12:10 – 14.00
Dining Hall
Gerhard Rempe
Max-Planck-Institute for Quantum Optics, Garching, Germany
Atoms and Photons for Quantum Information Processing
Immanuel Bloch
Institut für Physik, Johannes Gutenberg Universität Mainz,
Germany
Entangling Neutral Atoms in Optical Lattices
Lunch
Theory II
2006
11
QIP 2006
12
14:00 – 14:40
Hall 14
14:40 – 15:20
Hall 14
15:20 – 15:40
Hall 14
15:40 – 16:00
Hall 14
16:00 – 16.30
Foyer
P ROGRAM
Guido Burkard
Department of Physics and Astronomy, University of Basel,
Switzerland
Manipulating Electron Spin Qubits with Photons
Martijn Wubs
Institut für Physik, University of Augsburg, Germany
Landau-Zener transitions in circuit QED
Andrew D. Greentree
Centre for Quantum Computer Technology, School of
Physics, University of Melbourne, Australia
Adiabatic Transport in Solid-State Qubit Systems
Stefan Kehrein
Dept. für Physik and CENS, LMU München, Germany
Real Time Evolution of Dissipative Quantum Systems
Coffee Break
Semiconductor Systems I
16:30 – 17:10
Hall 14
Kohei M. Itoh
Department of Applied Physics, Keio University and
CREST-JST, Yokohama, Japan
Recent Progress towards Silicon-Based Quantum Computing
Dane R. McCamey
Centre for Quantum Computer Technology, The University
of New South Wales, Kensington, Australia
Spin and Charge Properties of Si:P Probed Using IonImplanted Nanostructures
Dominique Bougeard
Walter Schottky Institut, TU München, Germany
Magnetic and Structural Properties of GeMn: on the Way
to a DMS?
17:10 – 17:40
Hall 14
17:40 – 18:00
Hall 14
18:00
Dining Hall
Dinner
19:00
SR1, SR2
Poster Session
SFB 631
P ROGRAM
QIP 2006
Friday, May 26, 2006
Quantum Optics meets Solid State II
08:30 – 09:10
Hall 14
09:10 – 09:50
Hall 14
09:50 – 10:10
Hall 14
10:10 – 10.40
Foyer
Ad Lagendijk
FOM-Institute for Atomic and Molecular Physics
(AMOLF), Amsterdam, The Netherlands
Quantum Optics and Multiple Light Scattering
Jozsef Fortagh
Physikalisches Institut, University of Tübingen, Germany
Bose-Einstein Chips and Micro Atom Optics
Michael Kaniber
Control of Single Quantum Dot and Collective Spontaneous Emission in 2D Photonic Crystal Nanostructures
Coffee Break
Theory III – Optimum Control
10:40 – 11:30
Hall 14
Frank Wilhelm
IQC and Physics Department, University of Waterloom,
Canada
Optimum Control of Superconducting Qubits
Thomas Schulte-Herbrueggen
Department of Chemistry, TU-München, Germany
Quantum Compilation by Optimal Control
11.30 – 12:00
Hall 14
12:00 – 14.00
Dining Hall
Lunch
Semiconductor Systems II
14:00 – 14:40
Hall 14
Andy S. Sachrajda
IMS, NRC, Ottawa, Canada
2006
13
QIP 2006
14
14:40 – 15:10
Hall 14
15:10 – 15:40
Hall 14
15:40 – 16.10
Foyer
P ROGRAM
Triple Few Electron Quantum Dots - The Stability Diagram and Electron Transport
Stefan Ludwig
CeNS and Department für Physik, LMU München, Germany
A Double Dot Quantum Ratchet Driven by an Independently Biased Quantum Point Contact
Alexander Hohlleitner
Center for NanoScience, LMU München, Germany
Suppression of Spin Relaxation in n-InGaAs-Wires
Coffee Break
Semiconductor Systems III
16:10 – 16:30
Hall 14
16:30 – 17:00
Hall 14
17:00 – 17:15
Hall 14
Julien Gabelli
Laboratoire Pierre Aigrain, E.N.S., Paris, France
Relaxation Time of a Coherent RC Circuit
Emily C. Clark
Optically Probing Spin and Charge Interactions in a Tunable Artificial Molecule
Rudolf Gross
Workshop Closing
SFB 631
Oral Presentations
WMI
2µm
SC-Qubit
2µm
15
O RAL P RESENTATIONS
QIP 2006
Abstracts: Invited Talks
Fux qubits and their readout
C. Harmans
Kavli Institute of NanoScience, Delft University of Technology, Delft, The Netherlands
Small superconducting flux-based circuits may act as interesting quantum mechanical entities.
They show strong potential for quantum information processing as quantum bits or qubits,
as well as being of fundamental interest to study coherent quantum dynamics in a condensed
matter environment with many degrees of freedom. Crucial is the role of the interaction with
this environment, in respect to the critical balance between qubit control and readout versus
the requirement for an unperturbed dynamical system evolution. In recent experiments it has
been shown that flux-based circuits show large dephasing (and relaxation) times with extensive
tunability and in situ optimization. In addition qubit state readout has shown considerable
improvement.
Here we concentrate on single and multiple qubit systems, considering high visibility readout
and qubit-qubit coupling. We discus our recently introduced fast, dispersive inductive qubit
state readout method, which shows a strongly improved 87% readout visibility. Experimental
results of (conditional) spectroscopy of directly coupled qubits will be shown. Earlier results
on coupling a qubit to a harmonic oscillator will be discussed. This indicates the viability of
dynamic qubit-qubit coupling schemes using (red/blue) sideband excitation. All these ingredients make us believe that a scalable few-fluxqubit system is viable.
2006
17
18
QIP 2006
A BSTRACTS : I NVITED TALKS
Concept of adiabatic computation with superconducting flux qubits — first experimental results.
E. Il’ichev (1), S.H.W. van der Ploeg(1,2), M. Grajcar(1,3), A. Izmalkov(1), U. Huebner(1), H.-G. Meyer(1).
(1)Institute for Physical High Technology, P.O.Box 100239, D-07702 Jena, Germany,
(2)MESA+ Research Institute and Faculty of Science and Technology, University of
Twente,P.O. Box 217, 7500 AE Enschede, The Netherlands,
(3)Department of Solid State Physics, Comenius University, SK-84248 Bratislava, Slovakia
Controllable adiabatic evolution of a multi-qubit system can be used for adiabatic quantum
computation (AQC). This evolution ends at a configuration at which the Hamiltonian of the
system encodes the solution of the problem to be solved. As first steps towards a realization of
AQC we have investigated two, three and four flux qubit systems. These systems were characterized by making use of a radio-frequency method. We designed two-qubit systems with
coupling energy up to several kelvins. For three-flux-qubit systems we determined the complete ground-state flux diagram in the three dimensional flux space around qubits common
degeneracy point. For four-qubits samples we experimentally realized ferromagnetic as well
as antiferromagnetic coupling. We also showed that the system’s Hamiltonian could be completely reconstructed from our measurements. Problems of implementation of AQC by making
use of flux qubits are discussed.
SFB 631
QIP 2006
Circuit QED: Superconducting Qubits and Cavities
D. I. Schuster, A. Blais, J. Gambetta, A. Houck, J. Schreier, B. Johnsson, J. Chow, L.
Frunzio, J. Majer, M. H. Devoret, S. M. Girvin, R. J. Schoelkopf, J. Fink, M. Goeppl, R.
Bianchetti
Yale University and ETH Zurich
In recent experiments we have demonstrated the resonant coherent coupling of individual photons to a single qubit implemented as a Cooper pair box in a high quality superconducting
cavity [1]. In the non-resonant case, the dispersive coupling between the qubit and the cavity field is used to perform quantum non-demolition (QND) measurements of the qubit state
[2]. Using this read-out technique we have performed high visibility measurements of Rabi
oscillations and Ramsey fringes [3]. We analyze the single shot fidelity of the measurement
and discuss approaches to realize two-qubit gates in the circuit QED architecture [4] using the
cavity as a non-local coupling bus. Realizing photon-qubit coupling strengths in excess of 100
MHz we have recently been able to directly probe coherent and thermal photon distributions
in the cavity in the dispersive limit [5].
[1] A. Wallraff et al. Nature (London) 431, 162 (2004)
[2] D. I. Schuster et al. Phys. Rev. Lett. 94, 123602 (2005)
[3] A. Wallraff et al. Phys. Rev. Lett. 95, 060501 (2005)
[4] A. Blais et al. Phys. Rev. A 69, 062320 (2004)
[5] J. Gambetta et al. cond-mat/0602322 (2006)
2006
19
QIP 2006
20
Quantum Simulations with Trapped Ions
D. Porras, I. Cirac
Max-Planck Institute for Quantum Optics, Garching, Germany
Trapped ions at very low temperatures have been recognized as one of the most promising
approach to scalable quantum computing. In this talk I will show that with the same system
one should be able to perform quantum simulations in a simple and efficient way. In particular,
one could implement many-body models for spin systems, or Hubbard models.
One of the most important features is the presence of relatively long interactions in those systems, which give rise to new physical phenomena. Apart from that, I will show that one quantum computation is possible with large number of ions trapped in magnetic traps.
SFB 631
QIP 2006
Solid-state nuclear magnetic resonance-based quantum information processing:
what can we learn?
J. Baugh (1), O. Moussa (1), C. A. Ryan (1), R. Laflamme (1), C. Ramanathan (2), D.
G. Cory (2)
(1) Institute for Quantum Computing, Waterloo, Canada,
(2) Department of Nuclear Science and Engineering, MIT, USA
This talk will focus on motivations for pursuing solid-state NMR qubits, what we can learn
from this endeavour, and steps along the way (both recent accomplishments and future goals).
In brief, we are motivated by (a) the prospect of long nuclear spin-1/2 coherence times in spindilute solids, limited mainly by control capabilities; and (b) the prospect of reaching nuclear polarizations near unity through dynamic nuclear polarization techniques. Recent experimental
results in a three-qubit ensemble system demonstrate high-fidelity, universal control pertinent
to the control/coherence problem. Moreover, we show controlled selective qubit interactions
with a surrounding spin bath allowing for entropy-reducing operations such as algorithmic
cooling [1] and ultimately quantum error correction. These experiments are meant to explore
and push the boundaries of experimentally achievable control in the NMR context, with the
expectation that similar hurdles will be faced in other solid-state QIP implementations.
[1] J. Baugh, O. Moussa, C. A. Ryan, A. Nayak and R. Laflamme. Nature 438, 470-473 (2005).
2006
21
QIP 2006
22
Atoms and Photons for Quantum Information Processing
Gerhard Rempe
Institut für Quantenoptik, Hans-Kopfermann-Str. 1, Garching bei München, Germany
to be submitted
SFB 631
QIP 2006
Entangling Neutral Atoms in Optical Lattices
I. Bloch
Johannes Gutenberg University, Mainz
Neutral atoms in optical lattice offer powerful possibilities for the simulation of many-body
Hamiltonians, the generation of highly number squeezed states and the production of highly
entangled many-particle states for quantum information purposes. In my talk I will review
recent efforts to create such highly entangled many particle states with neutral atoms in optical
lattices. A novel detection techniques based on Hanbury Brown & Twiss type quantum noise
correlations in expanding ultracold atom clouds will be furthermore presented and applications for the read-out of novel quantum many body phases of a neutral atom based quantum
simulator will be discussed.
2006
23
QIP 2006
24
Manipulating electron spin qubits with photons
Guido Burkard
University of Basel, Switzerland
Single electron spins in semiconductor quantum dots are being initialized, manipulated, coherently coupled to other spins, and read out, all with on-chip electrical control, and are thus
promising candidates for the implementation of solid-state quantum information processing.
In this theoretical talk, we argue that further advantages in quantum coherence and control
can be gained by coupling the electron spins to photons, either via inter-band transitions in the
semiconductor material using optical light or via intra-band transitions in a microwave cavity. In the former case, excitation with a pair of applied laser fields at a two-photon resonance
between the two electron spin states and a charged exciton state can act as a weak quantum
measurement on the nuclear spin ensemble surrounding the electron. This optical process can
be used to bring the nuclear ensemble close to an eigenstate of the nuclear field operator that
couples to the electron spin, and thus to prolong the electron spin coherence time which is
limited by nuclear-spin induced dephasing. In the second case (intra-band transitions), we
show that deterministic quantum gates between two encoded spin qubits separated by up to
a centimeter can be implemented by embedding the host quantum dots into a superconducting microstrip cavity. The coherent interaction between the two distant qubits is mediated by
virtual photons in the common cavity mode.
SFB 631
QIP 2006
Landau-Zener transitions in circuit QED
M. Wubs(1), K. Saito(2), S. Kohler(1), Y. Kayanuma(3), and P. Hänggi(1)
(1) Institut für Physik, Universität Augsburg, Universitätsstrasse 1, D-86135 Augsburg, Germany,
(2) Department of Physics, Graduate School of Science, University of Tokyo, Tokyo 113-0033,
Japan,
(3) Department of Mathematical Science, Graduate School of Engineering, Osaka Prefecture
University, Sakai 599-8531, Japan.
Recent experiments showed that superconducting circuits can behave as the electronic analogue of cavity quantum electrodynamics: A qubit interacts with a quantum harmonic oscillator. A decisive advantage of circuit QED is that parameters are highly tunable. Topic of this
talk is the manipulation of a qubit via Landau-Zener transitions, in particular by transitions
that are caused by the coupling to a circuit-QED oscillator. By summing up an infinite-order
perturbation series, we determine the exact nonadiabatic transition probability, which turns
out to be independent of the oscillator frequency. After the Landau-Zener sweep, qubit and
oscillator are entangled in an intriguing manner. Novel single-photon generation emerges in
the strong-coupling limit. When generalizing the circuit QED model to the coupling to many
oscillators, we find that the transition probability depends on the total coupling strength. This
in turn allows a robust measurement of the quantum dissipation strength.
2006
25
QIP 2006
26
Recent progress towards silicon-based quantum computing
K. M. Itoh
Keio University and CREST-JST
Our progress towards realization of the silicon solid-state quantum computer [PRL, 89, 017901
(2002) and modified version of it] is reported. We show first experimental realization of a linear
single array of 29 Si stable isotopes which is a basic building block of our quantum computer
[PRL, 95, 106101 (2005)]. We also show experimentally that the phase decoherence time T2 of
29 Si nuclear spins in single crystal Si at room temperature can be extended up to 25 sec (and
possibly more) using RF decoupling techniques [PRB, 71, 014401 (2005)]. In parallel, electron
spins bound 31 P donors are found to have T2 up to msec and can be entangled efficiently to
31 P nuclear spins as well as to nearby 29 Si nuclear spins [PRB, 70, 033204 (2004)]. We show that
detection of these electron spins bound to 31 P donors is possible not only with electron spin
resonance but also with photoluminescence and photocurrent measurements, through which
quantum measurement of 31 P nuclear spins is also possible. Such new techniques will be useful
for the initialization and detection of electron and nuclear spin qubits in silicon.
SFB 631
QIP 2006
Spin and charge properties of Si:P probed using ion-implanted nanostructures
D.R. McCamey (1,2) , H. Huebl (3), M. S. Brandt (3), V.C. Chan (1,2), T.M. Buehler
(1,2∧ ), A.J. Ferguson (1,2), D.J. Reilly (1,2), W. D. Hutchison (1,4), J. C. McCallum
(1,5), A. R. Hamilton (2), A.S. Dzurak (1,2), C. Yang (1,5), D.N. Jamieson (1,5) and R.
G. Clark (1,2)
(1)Australian Research Council Centre of Excellence for Quantum Computer Technology
(2)School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia
(3)Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, D-85748
Garching, Germany
(4)School of Physical, Environmental and Mathematical Sciences, University College, The
University of New South Wales ADFA, Canberra, ACT 2600, Australia and
(5)School of Physics, University of Melbourne, VIC 3010, Australia
(*) Now at ABB Switzerland, Corporate Research.
(∧ ) Now at Dept. Physics, Harvard University, Cambridge, 02138, USA.
The fabrication of nanoscale devices in silicon via ion-implantation is a useful tool for the
study of both charge and spin properties. This talk focuses on two types of devices; an ionimplanted single electron transistor (SET), useful for the study of charge states in silicon, and
ion-implanted Si:P electrically detected magnetic resonance (EDMR) devices.
For both types of device, fabrication involves selective ion implantation into regions previously
defined by EBL of a PMMA mask layer. For the SET, a small (500nm x 70nm) metallic island
with two leads is fabricated. A nearby Al-AlOx-Al SET is used to probe the charge state of the
Si-SET. We observe single electron charging of the device, as well as the effect of disorder on
the tunnel coupling.
To probe the spin properties of the Si:P system, we have fabricated nanoscale source-drain contacts via ion-implantation to restrict current through the device to a very small sample region
(∼100nm x 100nm x 15nm). Phosphorus is implanted into this region at a dose below the metalinsulator transition. By using electrically-detected magnetic resonance (EDMR), which probes
the spin properties of the donors via spin dependent recombination processes in the current,
we are able to spectroscopically investigated systems with as few as 100 donors. The ability
to study the spin states of few donors in the solid state has numerous applications in areas
ranging from classical memory storage to quantum computation.
2006
27
QIP 2006
28
Quantum optics and multiple light scattering
Ad Lagendijk
FOM-Institute for Atomic and Molecular Physics (AMOLF), Amsterdam, The Netherlands
Multiple light scattering in random media is often assumed to wipe out many, if not all, quantum correlations. We will show (theory and experiment) however that a number of correlations
survive multiple light scattering in linear media.
We also explored the effect of multiple scattering in the regime where saturation of the scatterers plays a role. We investigate the lasing threshold of a system consisting of a few scatterers,
of which one has gain.
SFB 631
QIP 2006
Bose-Einstein Chips and Micro Atom Optics
Jozsef Fortagh
Physikalisches Institut, Universität Tübingen, Germany
Bose-Einstein condensates can be trapped, moved, and coherently manipulated with the magnetic fields generated by microfabricated current conductors at the surface of a chip. Recently
we have observed Bragg diffraction of a condensate from an integrated purely magnetic lattice. Furthermore a matter wave interferometer has been realized by observing the interference
pattern of overlapping diffraction orders. The interferometer demonstrates the feasibility of
the construction of integrated precision sensors for forces, acceleration and rotation. The BoseEinstein-chip may also serve as the starting point for single atom matter wave physics on a
chip. Efficient single atom detection as a crucial prerequisite for such a scenario should be
possible by optical ionisation and subsequent ion detection with an suitable channeltron detector. If single atom detection and manipulation will turn out to be successful, the recently
discussed schemes for quantum information processing on such chips may be pursued also
experimentally.
2006
29
QIP 2006
30
Triple Few Electron Quantum Dots - The Stability Diagram and Electron Transport
A.S. Sachrajda, L. Gaudreau, S. Studenikin, J. Lapointe, A. Kam, M. Korkusinski and
P. Hawrylak
IMS, NRC, Ottawa, Canada
Over the last few years the combination of few electron quantum dots and charge detection has
led to dramatic developments in the area of single spin and charge qubits. These experiments
have involved single and coupled few electron quantum dots. There has recently been growing
theoretical interest in the next level of complexity triple few electron dots, the artifical triatom.
In this talk I will describe experiments on a triple few electron quantum dot potential.
The stability diagram of the triple dot potential is mapped out in the few electron regime,
creating a new playground for future quantum information applications. Important regimes
are identified e.g. (1,1,1) - the starting configuration for GHz states. Quadruple points are
demonstrated where four different configurations become degenerate. In the vicinity of the
quadruple points we observe a novel phenomenon as charge transfer lines are duplicated due
to charge and spin reconfigurations. These effects are also reminiscent of quantum cellular
automata.
Preliminary transport experiments have also been performed through the triple dot and will be
described. Low magnetic field experiments in the vicinity of quadruple points reveal magnetoconductance fluctuations that have many properties reminiscent of phase rigitiy effects first
observed in transport experiments through quantum rings.
SFB 631
QIP 2006
Abstracts: Contributed Talks
Macroscopic quantum tunneling in intrinsic Josephson junctions
X.Y. Jin, J. Lisenfeld, Y. Koval, A. Lukashenko, A.V. Ustinov, and P. Müller
Physikalisches Institut III, Universität Erlangen-Nürnberg, Erwin-Rommel-Strasse 1, D91058 Erlangen, Germany
We have investigated macroscopic quantum tunneling in Bi2 Sr2 CaCu2 O8+δ intrinsic Josephson
junctions at millikelvin temperatures using microwave irradiation. Measurements show that
the escape rate for uniformly switching stacks of N junctions is about N 2 times higher than that
of a single junction having the same plasma frequency. We argue that this gigantic enhancement of macroscopic quantum tunneling rate in stacks is boosted by current fluctuations which
occur in the series array of junctions loaded by the impedance of the environment.
2006
31
32
QIP 2006
A BSTRACTS : C ONTRIBUTED TALKS
Flux Qubit Readout via a Capacitive Bias
F. Deppe(1,2,3), S. Saito(2,3), K. Kakuyanagi (2,3), T. Meno(4), K. Semba(2,3), H.
Takayanagi(2,3), and R. Gross(1)
(1)Walther-Meissner-Institut, Garching, Germany,
(2)NTT BRL, NTT Corp., Atsugi, Japan,
(3)CREST JST, Saitama, Japan,
(4)NTT AT, NTT Corp., Atsugi, Japan
Measuring a solid state based quantum two level system allows a better understanding of the
interaction of these systems with their environment. As a particular example we present the
results of measurements on an aluminum based superconducting three Josephson juntion flux
qubit. The qubit state, which corresponds to circulating currents of opposite polarity, is read
out via the switching signal of a dc superconducting quantum interference device (SQUID)
mutually coupled to the qubit. In contrast to many other experiments we use a capacitor and
not a resistor to create the SQUID bias current, thereby creating a different electromagnetic
environment which e.g. allows for faster readout pulses at similar filtering conditions.
For one and the same qubit we show microwave spectroscopy results, Rabi oscillations, Ramsey fringes, and spin echo decay for both capacitive and resistive SQUID bias. Careful analysis
reveals that the capacitive method improves visibility but shortens T1 and T2 in our experimental configration. Finally we discuss shortcomings of the present experiments and prospects for
future experiments.
This work was partly supported by the Sonderforschungsbereich 631 of the Deustche
Forschungsgemeinschaft.
SFB 631
QIP 2006
On-Chip Microwave Fock States and Quantum Homodyne Measurements
M. Mariantoni(1), M.J. Storcz(2), F.K. Wilhelm(2), W.D. Oliver(3), A. Emmert(1), A.
Marx(1), R. Gross(1) H. Christ(4), and E. Solano(4,5)
(1)Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Walther-MeissnerStrasse 8, D-85748 Garching, Germany
(2)Department Physik, CeNS and ASC, LMU, Theresienstrasse 37, D-80333 Muenchen, Germany
(3)MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachussets 02420, USA
(4)Max-Planck Institute for Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching,
Germany
(5)Seccion Fýsica, Departamento de Ciencias, Pontificia Universidad Catolica del Peru,
Apartado 1761, Lima, Peru
We propose a method to couple metastable flux-based qubits to superconductive resonators
based on a quantum-optical Raman excitation scheme that allows for the deterministic generation of stationary
and propagating microwave Fock states and other weak quantum fields. Moreover, we introduce a suitable microwave quantum homodyne technique, with no optical counterpart, that
enables the measurement of relevant field observables, even in the presence of noisy amplification devices.
2006
33
QIP 2006
34
Efficient on-chip source of microwave photon pairs
F. Marquardt
Sektion Physik der LMU München, Center for NanoScience and Arnold-Sommerfeld-Center for
Theoretical Physics, Munich, Germany
We describe a scheme for the efficient generation of microwave photon pairs by parametric
downconversion in a superconducting transmission line resonator coupled to a Cooper pair
box serving as artificial atom. By properly tuning the first three levels with respect to the cavity
modes, the downconversion probability may become higher than in the most efficient schemes
for optical photons. We show this by numerically simulating the dissipative quantum dynamics of the coupled cavity-box system and discuss the effects of dephasing and relaxation. The
setup analyzed here might form the basis for a future on-chip source of entangled microwave
photons.
SFB 631
QIP 2006
Entanglement of mixed states with GHZ and W state components
Robert Lohmeyer (1), Andreas Osterloh (2), Jens Siewert (1,3), Armin Uhlmann (4)
(1) Institut fuer Theoretische Physik, University of Regensburg, 93040 Regensburg, Germany,
(2) Institut fuer Theoretische Physik, University of Hannover, 30167 Hannover, Germany,
(3) DMFCI, University of Catania, 95125 Catania, Italy,
(4) Institut fuer Theoretische Physik, University of Leipzig, 04109 Leipzig, Germany
Characterizing entanglement of multipartite mixed states is a fundamental issue in quantum
information theory for which there is no general theory. We have investigated the entanglement
properties of mixed three-qubit states composed of a GHZ state and a W state orthogonal to the
former. In particular we have found the optimal decompositions and the convex roofs for the
three-tangle, and we have analyzed the Coffman-Kundu-Wootters inequality for this family of
mixed states. The results reveal intriguing differences compared to the properties of two-qubit
mixed states. In particular we find that, the well-known monogamy of entanglement can be
lifted for mixed states.
2006
35
36
QIP 2006
Adiabatic transport in solid-state qubit systems
A. D. Greentree(1), L. C. L. Hollenberg(1), C. J. Wellard(1), A. G. Fowler(1,2), and S. J.
Devitt(1)
(1) Centre for Quantum Computer Technology, School of Physics, University of Melbourne,
Melbourne, Victoria 3010, Australia
(2) Institute for Quantum Computing, University of Waterloo, Waterloo, ON, N2L 3G1,
Canada
Solid state quantum computer architectures are often touted as inherently scalable on the basis of the historical scaling of classical architectures – i.e. through sheer ease of component
replication. However, this weak scaling argument misses the vast complexity of the implementation of fault-tolerant quantum protocols required to protect quantum information processing
against errors. In the design of truly scalable quantum computer architectures, highly nontrivial requirements such as qubit transport, logic gates between physically separated qubits,
fast read-out and resources for classical feed-forward processing in error correction must be
taken into account. We present a new adiabatic scheme: CTAP, Coherent Tunneling Adiabatic
Passage, for physical qubit transport particularly suited to solid-state systems. Several applications immediately follow, including a 2D donor electron spin architecture and a protocol for
generating entangled states across non-local qubits.
SFB 631
QIP 2006
Real time evolution of dissipative quantum systems
S. Kehrein (1) and A. Hackl (2)
(1) Department für Physik and CENS, LMU München, Germany,
(2) Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Universität Augsburg, Germany
The out-of-equilibrium time evolution of interacting quantum many-body systems is a difficult theoretical problem, which is of key importance for the theoretical modeling of quantum
information processing with decohering environments. Recently, dramatic progress has been
made with new numerical methods like the time-dependent density matrix renormalization
group (DMRG) or numerical renormalization group (NRG). I will show that the flow equation
method allows a novel analytical approach to this problem, and permits to study the real time
evolution from short to long time scales. As an example I present results for the real time spin
evolution of the spin-boson model prepared in some entangled or non-entangled initial state,
which is a ubiquitous problem in quantum information processing.
2006
37
38
QIP 2006
Magnetic Properties of GeMn: on the way to a group IV DMS?
Dominique Bougeard(1), Stefan Ahlers(1), Achim Trampert(2), Narayan Sircar(1), and
Gerhard Abstreiter(1)
(1) Walter Schottky Institut, TU München, Garching, Germany
(2) Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany
Diluted magnetic semiconductors (DMS) open new perspectives for the realisation of devices
combining band-engineering and magnetic non-volatility. The Si-Ge system has attracted special interest because of its compatibility with the mature and widespread Si technology. A
promising publication on GeMn claiming ferromagnetism up to 116 K [1] has recently been
questioned by a comprehensive work reporting ferromagnetism only below 12 K [2] for comparable samples.
We present the first detailed study of the relationship between nanostructure and magnetic
properties of precipitate-free, MBE grown GeMn. The material is DMS-like from the structural
point of view but shows no global spontaneous magnetisation.
Our study shows hints for carrier induced ferromagnetism within coherent clusters, indicating
a way to the realisation of a group IV DMS.
[1] Y.D. Park et al., Science, 295, 651 (2002)
[2] A.P. Li et al., Phys. Rev. B, 72, 195205 (2005)
SFB 631
QIP 2006
Control of single quantum dot and collective spontaneous emission in 2D photonic
crystal nanostructures
M. Kaniber(1), F. Hofbauer(1), S. Grimminger(1), M. Bichler(1), G. Abstreiter(1), and
J.J. Finley(1)
(1)Walter Schottky Institut, Am Coulomball 3, 85748 Garching, Deutschland
We present investigations of the coupling of InGaAs quantum dots (QD) to both extended and
strongly localised optical modes in 2D photonic crystal nanostructures. By measuring the local QD spontaneous emission rate (Rspon ) we probe the photonic DOS at frequencies throughout the photonic bandgap (PBG) and close to localised modes at single missing hole defects
(Q∼10000, Vmode < 0.5(λ /n)3 ). For QD emitting into the PBG but detuned from the cavity
mode, we observe a strong suppression of Rspon compared to its value in a homogenous photonic environment (R0 /Rspon =30±6) due to the reduced photon DOS. In contrast, for QD coupled to the cavity modes we measure 1/Rspon ∼50ps, corresponding to a large (Rcavity /R0 =18x)
Purcell enhancement of Rspon over the intrinsic value (R0 ). Single dot measurements reveal clear
photon anti-bunching for individual QD spectrally detuned from the cavity mode. Most surprisingly, for the same sample anti-bunching is not observed for single QD that are spectrally
and spatially coupled to the cavity, which may be a signature for the occurrence of superradiant
emission from the few QD coupled to a common cavity mode or a transition to low threshold
lasing.
2006
39
40
QIP 2006
Optimum control of superconducting qubit systems
F.K. Wilhelm (1,2), A. Spoerl (3), T. Schulte-Herbrueggen (3), S.J. Glaser (3), M.J.
Storcz (2), J. Ferber (2), and P. Rebentrost (1,2)
(1) IQC and Physics Department, University of Waterloom, Canada
(2) Physics Department, CeNS, and ASC, University of Munich, Germany
(3) Chemistry department, Technical University of Munich, Germany
We apply the optimum control theory invented for NMR to superconducting qubit systems.
i) For coupled Cooper-pair boxes, we show how to implement a high-fidelity CNOT in short
time using shaped pulses. We discuss techniques to shape these pulses in purely dissipative
networks.
ii) For phase qubits, there is a crucial trade-off between speed and loss of fidelity due to leakage
to higher states. We wil discuss how to improve the fidelity of single-qubit rotations in this
system using shaped pulses.
SFB 631
QIP 2006
Quantum Compilation by Optimal Control
T. Schulte-Herbrueggen (1), A.K. Spoerl (1), N. Khaneja (2), and S.J. Glaser (1),
(1) TU-Munich
(2) Harvard University
Decomposing a quantum gate or module into a sequence of universal gates often looses the
race against decoherence. Optimal-control-based direct compilation is far more advantageous
as exemplified in spin [1] and pseudo-spin systems. In Josephson charge qubits, for example,
timeoptimal control gains two orders of magnitude [2] towards the error-correction threshold
as compared to pioneereing controls.
Here we extend our optimal control toolbox [3] by a quantum compiler under explicit relaxation. The new approach proves to be the method of choice in the generic case, whenever
the drift Hamiltonian would take the system outside decoherence-poor subspaces. Otherwise
timeoptimal controls already give highest fidelities.
Finally, we show how algorithmic modules (like the Quantum Fourier Transform, the indirect
SWAP etc) optimised for medium-sized quantum systems can be recursively used in larger
quantum systems thus giving significantly higher fidelities than standard decompositions into
universal one- and two-qubit modules.
References:
[1] Phys. Rev. A 72 (2005), 042331; and ”The Quantum Gate Design Metric”, submitted
[2] ”Optimal Control of Josephson Qubits”, quant-ph/0504202
[3] J. Magn. Reson. 172 (2005), 296; and NATO Proceedings, Crete 2005, in press
2006
41
42
QIP 2006
A double dot quantum ratchet driven by an independently biased quantum point
contact
V. Khrapay (1), S. Ludwig (1), J.P. Kotthaus (1), W. Wegscheider (2)
(1) Center for NanoScience and Department für Physik, Ludwig-Maximilians-Universität,
Geschwister-Scholl-Platz 1, 80539 München, Germany
(2) Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany
In this experiment we investigate the dynamic interaction between a double quantum dot
(DQD) and a nearby quantum point contact (QPC). An unbiased DQD acts as a current source,
if electrons are excited resonantly between the last filled state of one of the dots and the first
empty state of the other dot. The energy difference between these two states, called the asymmetry energy of the DQD, defines the resonance condition, while the sign of the asymmetry
energy specifies the direction of current. In this sense the DQD represents a special case of a
non-adiabatic energy selective tunable ratchet. In our experiment a biased QPC impeding an
electrically separate current circuit acts as the energy source driving the ratchet.
We measure current through the DQD in dependence of the DQD asymmetry and the QPC bias
voltage. As expected, the current direction through the DQD is only determined by the sign of
the DQD asymmetry and independent of the current direction through the QPC. We observe a
strong dependence of the amplitude of the current through the DQD on the QPC bias voltage.
By tuning the asymmetry energy of the DQD the spectrum of the energy source defined by
the QPC can be probed. We find a wide band energy spectrum. Stricingly, our observations
are inconsistent with a standard model of voltage fluctuations related to shot noise in a QPC.
Possible ratchet mechanisms will be discussed.
SFB 631
QIP 2006
Suppression of Spin Relaxation in n-InGaAs-Wires
A.W. Holleitner
Center for NanoScience (CeNS), Munich
For an efficient information processing scheme based upon the electron spin, it is important to
explore carrier spin relaxation mechanisms in nanostructures as a function of dimensionality.
In two and three dimensions, elementary rotations do not commute, with significant impact on
the spin dynamics if the spin precession is induced by spin-orbit coupling. Spin-orbit coupling
creates a randomizing momentum-dependent effective magnetic field; the corresponding relaxation process is known as the D’yakonov-Perel’ mechanism. In an ideal one-dimensional
system, however, all spin rotations are limited to a single axis, and the spin rotation operators
commute. In the regime approaching the one-dimensional limit, a progressive slowing and
finally a suppression of the D’yakonov-Perel’ spin relaxation have been predicted.
We report on spin dynamics of electrons in narrow two-dimensional n-InGaAs channels as a
function of the wire width [1]. We find that electron-spin relaxation times increase with decreasing channel width, in accordance with recent theoretical predictions. Surprisingly, the
suppression of the spin relaxation rate can be detected for widths that are an order of magnitude larger than the electron mean free path. We find the spin diffusion length and the wire
width to be the relevant length scales for explaining these effects.
We acknowledge financial support by AFOSR and ONR.
[1] A.W. Holleitner, V. Sih, R.C. Myers, A.C. Gossard, and D.D. Awschalom, cond-mat/0602155.
2006
43
QIP 2006
44
Relaxation time of a coherent RC circuit
J. Gabelli(1)(4), G. Fève(1), J.-M. Berroir(1), B. Plaçais(1), Y. Jin(2), U. Gennser(2), B.
Etienne(2), D.C. Glattli(1)(3)
(1)Laboratoire Pierre Aigrain, E.N.S., 24 rue Lhomond, 75231 Paris Cedex 05, France,
(2)Laboratoire de Photonique et Nanostructure, CNRS , route de Nozay, 91 Marcoussis, France,
(3)Service de Physique de l’Etat Condensé, C.E.A. Saclay, 91191 Gif-sur-Yvette, France,
(4)Department für Physik, Ludwig-Maximilians-Universität München, Geschwister-SchollPlatz 1, 80539 Müunchen, Germany
Solid-state based nanoscale systems open up the perspective of fabricating large integrated
networks that would be required for realistic applications of quantum information processing.
Examples involving a two dimensional electron system (2DES) are flying qubits on quantum
edge states [1] or spin qubits in double quantum dots [2,3]. However, coherent manipulation of
such a qubit requires detailed knowledge of its high frequency dynamics. We have performed
radio frequency transport measurements through a microscale RC-circuit at temperatures in the
range of T 100 mK. The RC-circuit is defined by a large electron droplet coupled capacitively
to a top gate and via a quantum point contact (QPC) to the 2DES. In the quantum hall regime
with filling factor ν = 2, we observe strong oscillations of the imaginary part of the circuit
impedance in dependence of a gate voltage, which are related to Coulomb oscillations of the
electron droplet. In contrast, the real part of the impedance stays constant at the value of
Re( Z ) = h/2e2 , which is half of the value expected for an isolated QPC. This signature is
only possible for a fully coherent quantum circuit. Our results are in accordance with a fully
coherent scattering theory developed by A. Prêtre, H. Thomas and M. Büttiker [4].
[1] PRA 63,050101(R)(2001)
[2] PRA 57,120-126 (1998)
[3] PRL 91,226804(2003), Science 309,2180(2005),Science 309,1346-1350(2005)
[4] PRA 180,364(1993),PRL 70,4114 (1993)
SFB 631
QIP 2006
Controlled Hybridization of Neutral and Charged Excitons in Self-Assembled
Quantum Dot Molecules
E. C. Clark(1), H. J. Krenner(1), C. Scheurer(2), T. Nakaoka(1), M. Sabathil(1), M.
Bichler(1), Y. Arakawa(2), G. Abstreiter(1) and J. J. Finley(1)
(1)Walter Schottky Institut and Physik Department, Technische Universität München, Am
Coulombwall 3, D-85748 Garching, Germany, email:[email protected]
(2)Lehrstuhl für Theoretische Chemie, Technische Universität München Lichtenbergstraße 4,
D-85748 Garching, Germany
Qubits formed from interband charge excitations (excitons) in semiconductor quantum dots
(QDs) represent a particularly attractive system since they can be coherently manipulated using
picosecond laser pulses. An important step is to achieve coherent coupling of quantum states
in spatially sepa-rated QDs to realize a system with conditional coherent dynamics that can be
electrically and opti-cally manipulated.[1]
We report recent experiments in which we electrically manipulate coupled excitonic states
(neutral and negatively charged single excitons) in individual QD-molecules using static electric fields. The samples investigated consist of a single pair of vertically stacked, self assembled
InGaAs QD-molecules embedded in an n-type GaAs Schottky photodiode. This device geometry enables us to control the coherent coupling between excitonic states in the upper and lower
dots by tuning the electric field oriented along the axis of the QD-molecule. At low excitation
power densities, field dependent luminescence reveals a clear anticrossing of spatially direct
(e,h in the same dot) and indirect (e,h in different dots) neutral excitons. The spectrum and
controlled hybridization of nega-tively charged excitons is shown to be much richer due to the
complex spectrum of three particle states (X-=2e+1h) that can exist in a QD-molecule.
Supported by the DFG via SFB631, Projects B1 and B5.
[1] H. J. Krenner et al., Phys. Rev. Lett. 94, 057402 (2005)
2006
45
Poster Presentation
CeNS
47
P OSTER P RESENTATION
QIP 2006
Abstracts:
Poster Presentations
How fat is Schroedinger’s cat?
B. Abel(1,2,3), Florian Marquardt(1,2,3), Jan von Delft(1,2,3)
(1)Ludwig-Maximilians University Munich, Department for Physics,
(2)Arnold Sommerfeld Center for Theoretical Physics,
(3)Center for Nanoscience
Recent experiments have tried to produce superpositions of ”macroscopically distinct” quantum states, e.g. in small superconducting quantum interference devices (SQUIDs) or in microwave cavities. These superpositions are commonly referred to as ”Schrödinger cat states”
(1). In this work, we provide an answer to the following important question: ”How ’macroscopic’ is such a superposition?”. We present a general measure of the distance between two
arbitrary many-body states forming such a superposition, going beyond previous works that
only considered a special class of possible states (2). After illustrating its general features,
we apply our measure to experiments employing three-junction SQUIDs (Mooij), where the
ground state at half a flux quantum is a superposition
of clockwise and counterclockwise flow√
ing supercurrents: |Ψi = (|lefti + |righti)/ 2.
[1] E. Schrödinger, ”Die gegenwärtige Situation in der Quantenmechanik”, Naturwissenschaften,
48, 807, 49, 823, 50,844 (1935).
[2] W. Dürr, C. Simon, and J. I. Cirac, Phys. Rev. Lett. 89, 210402 (2002).
[3] xs J. E. Mooij, et al., Science 285, 1036 (1999).
2006
49
QIP 2006
50
A BSTRACTS : P OSTER P RESENTATIONS
Magnetic Ge(Mn) nanostructures
Stefan Ahlers(1), Dominique Bougeard(1), Achim Trampert(2), Narayan Sircar(1), and
Gerhard Abstreiter(1)
(1) Walter Schottky Institut, TU München, Garching, Germany
(2) Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany
We report on the first comprehensive study relating the nanostructure of MBE-grown GeMn alloys to their magnetic properties. The formation of ferromagnetic intermetallic Mn5Ge3 precipitates in a Ge matrix is observed down to substrate temperatures TS of 70◦ C. The size and quantity of the precipitates can be tuned by the variation of the substrate temperature. Although
the thermomagnetic behaviour is very similar to reported GeMn diluted magnetic semiconductors, the magnetic properties of our material are clearly dominated by the influence of the
precipitates below the ferromagnetic ordering temperature of Mn5Ge3.
We have investigated the nanostructure of nominal Ge0.95Mn0.05 alloys grown in low temperature MBE at TS ranging from 120◦ C to 70◦ C. The epitaxy on (001)Ge is defect-free, but
transmission electron microscopy (TEM) shows the formation of precipitates which are incoherent with the surrounding matrix and have a hexagonal crystal structure. The precipitates
can be identified as Mn5Ge3. The precipitates are round and exhibit a preferred orientation.
Their size and quantity decreases with decreasing substrate temperature.
Zero field cooled, field cooled, time-dependent as well as magnetisation versus field measurements converge in a picture where the magnetic properties of the alloy between the ferromagnetic ordering temperature of Mn5Ge3 and a lower characteristic blocking temperature TB are
dominated by superparamagnetism of Mn5Ge3 precipitates. Below TB the magnetic signature of ferromagnetic precipitates with a preferred orientation in a non-ferromagnetic matrix
is observed. The volume of the precipitates, and thus also the magnetic moment and TB are
decreased by decreasing the substrate temperature in MBE.
SFB 631
QIP 2006
Manipulation of Nuclear Spins with Electrons Spins (and vice versa) in Quantum
Dots
H. Christ, G. Giedke, and J.I. Cirac
Max Planck Institut fuer Quantenoptik, Garching, Germany
The spin of an excess electron in a quantum dot is a promising candiate for a qubit. We
study the hyperfine interaction with the lattice of nuclei, which is in many situations of interest the strongest coupling to the environment. It is shown how the nuclear spin system can
be prepared efficiently via this interaction. The resulting polarized states will in turn leave
pronounced effects on the electron spin evolution. For highly polarized states a systematic
expansion of the nuclear spin operators in terms of bosonic mode operators is derived. The
resulting Jaynes-Cummings-like dynamics of the electron-nuclear system provides a versatile
tool for quantum information processing tasks.
2006
51
52
QIP 2006
Circuit Modeling of Nanosystems Interacting with Superconducting Resonators
G. Csaba, Z. Fahem, F. Peretti, P. Lugli
Institute for Nanoelectronics, Technical University of Munich
On-chip microwave spectroscopy is emerging as a powerful method to probe dynamic properties of quantum systems in the GHz frequency range. The design of such experimental setup
requires different levels of modeling: quantum-mechanical simulations, classical and quantum
electrodynamics and extensive microwave simulations of the read-out apparatus. Equivalent
circuit construction is a promising approach to simulate these different physical phenomena in
a unified environment.
Our work will present circuit simulation of flux qubits and nanoscale magnets, which are interacting with a superconducting coplanar resonator. The resonator is modeled by a three-port
equivalent circuit, extracted from three-dimensional finite-element simulations. This three-port
is connected to the equivalent circuit of the qubit, which - in the simplest case - is based on the
Bloch equations. As an example, we will simulate dispersive readout of various quantum systems with our circuit models.
SFB 631
QIP 2006
Charge carrier confinement in quantum dots and wires fabricated by cleaved edge
overgrowth
J. Ehehalt(1), R. Schuster(1), C. Gerl(1), M. Reinwald(1), D. Schuh(1), W. Wegscheider(1), M. Bichler(2), G. Abstreiter(2)
(1)Universität Regensburg, Germany,
(2)Walter-Schottky-Institut, TU München, Germany
The Cleaved Edge Overgrowth technique has been used to fabricate single and coupled quantum dots with precisely controlled sizes and positions. Conventionally three intersecting GaAs
quantum wells lead to the formation of a quantum dot at the junction due to quantum mechanical bound states with confinement energies of up to 10 meV.
In this work we focus on enhancing the charge carrier confinement in these QD structures
by introducing tensile strain between materials with different lattice constants. In order to
optimize the growth parameters we studied the effects of strain in quantum wires. Microphotoluminescence spectroscopy of purely strain-induced quantum wires shows confinement
energies of up to 52 meV. By combining conventional T-shaped wires with strain-induced confinement, much larger confinement energies are possible. Simulations predict confinement
energies of up to 108 meV. These results are now to be applied to fabricate improved quantum
dot stuctures.
We also present a technique to improve the interface smoothness of the overgrown layers,
which leads to sharper PL spectrum lines and better quantum dot conformity.
2006
53
54
QIP 2006
Implementation of two-cell flux qubits
A.K. Feofanov, A.A. Abdumalikov, A.V. Ustinov
Physikalisches Institut III, Universitaet Erlangen-Nuernberg, Erlangen, Germany
The standard flux qubit implemented at Delft [1] consists of a superconducting loop with three
Josephson junctions and features a double well potential at half frustration. Its limitation is
that the barrier height cannot be changed without breaking the symmetry of the potential.
An alternative device proposed by Yukon [2] is a two-cell flux qubit containing four junctions.
One of the useful properties of Yukon’s qubit is that the barrier height can be controlled without
violating the potential symmetry, which in turn permits implementation of geometric quantum
computation using a Cirac-Zoller [3] type of bus. We have established a technological process
for fabricating two-cell qubits based on sub-micron Al-AlOx-Al Josephson tunnel junctions
with a critical current density around 500 A/cm2. We have also developed read out circuits for
such qubits using inductive coupling. Results reflecting actual progress in this experiment will
be presented.
[1] I. Chiorescu et al., Science 299, 1869 (2003)
[2] S.P. Yukon, Physica C 368, 320 (2002)
[3] J.I. Cirac and P. Zoller, Phys. Rev. Lett. 74, 4091 (1995)
SFB 631
QIP 2006
Transmission through a two-level quantum dot
T. Hecht(1), C. Karrasch(2), V. Meden(2), Y. Oreg(3), J.v. Delft(1)
(1)Ludwig-Maximilians Universität München, ASC and CeNS, Germany,
(2)Universität Göttingen, Germany,
(3)Weizmann Institute of Science, Rehovot, Israel
The recent measurements of Schuster et al. [1] of the transmission phase through a quantum
dot embedded in one arm of an Aharonov Bohm interferometer contradict the simple models
that were used to describe the phase evolution so far, see e.g. [2]. Inspired by this experiment,
we study the transmission phase of a quantum dot embedded in one arm of a two path electron interferometer by solving a two-level Anderson model by means of Wilson’s numerical
renormalization group method and the functional renormalization group method.
Relating the scattering phase and the occupation of the levels at T = 0 using the Friedel sum
rule, we show that for a level spacing ∆ much bigger than the coupling to the leads Γ , the transmission always experiences a phase lapse of π as a function of gate voltage. This behaviour is
independent of the exact parameters of the quantum dot or the parity of the successive levels.
[1] R. Schuster, E. Buks, M. Heiblum, D. Mahalu, V. Umansky, H. Shtrikman, Nature 385, 417
(1997).
[2] U. Gerland et al., Phys. Rev. Lett. 84, 3710 (2000).
2006
55
56
QIP 2006
Fabrication and characterisation of Al/AlOx based superconducting
T. Heimbeck, K. Madek, M. Göppl, S. Dandl, A. Marx, R. Gross
Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching
Superconducting quantum bits (qubits) based on superconducting loops containing an odd
number of Josephson junctions with a coupling energy larger than the charging energy are
called flux qubits. The qubit states are given by a symmetric superposition of currents flowing
clockwise and counter-clockwise when being frustrated by applying a magnetic field corresponding to half a flux quantum in the loop. The system can be read out by a dc SQUID
comprising the qubit.
We are fabricating flux qubits based on Al/AlOx /Al tunnel junctions, using electron beam
lithography and shadow evaporation technique. A crucial point was to establish and optimise
the oxidation process for the lower electrode in order to fabricate Josephson junctions with
well defined critical currents. Furthermore, the design of the electromagnetic environment
is an important issue, which is required to isolate the qubit from environmental sources of
decoherence. Measurements on various test structures (Josephson junctions, SQUIDs, qubits)
were used to analyse and further optimise the fabrication parameters.
This work was supported by the Sonderforschungsbereich 631 of the Deutsche Forschungsgemeinschaft
SFB 631
QIP 2006
Hole Spin Relaxation in Self-Assembled InGaAs Quantum Dots
D. Heiss, S. Schaeck, M. Kroutvar, M. Bichler, G. Abstreiter, and J.J. Finley
Walter Schottky Institut, Garching, Germany
We present investigations of the spin dynamics of optically stimulated holes in self-assembled
quantum dots (QD). In the context of quantum information processing, fully localised holes
may be advantageous due to the p-like character of their Bloch wavefunction that strongly
suppresses coupling to the nuclear spin system.
For these experiments we use spin memory devices based on n-type Schottky diodes that enable selective optical generation, storage and readout of single hole spins in InGaAs-GaAs self
assembled quantum dots.
Our measurements show a significant polarization memory effect for holes with up to 12%
degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T1 in the microsecond range, with a lower limit of
∼100µs (B=3T, T=8K). For increasing magnetic field or temperature a reduction of the hole spin
lifetimes is observed.
2006
57
58
QIP 2006
On-chip single microwave photon detector in superconducting circuit QED
F. Helmer (1), M. Mariantoni (2), E. Solano (3), and F. Marquardt (1)
(1) Ludwig-Maximilians-Universitaet (Sektion Physik), CeNS and ASC, Munich, Germany,
(2) Walther-Meissner Institut, Garching, Germany,
(3) Max-Planck Institute for Quantum Optics, Garching, Germany
Superconducting circuit QED combines concepts from quantum and atom optics with those
from solid state physics. Microwave photons guided along superconducting transmission lines
on a chip interact with superconducting qubits. So far, a crucial element is missing in the
circuit QED toolbox: a single photon detector. Here, we propose and analyze a scheme that
implements single-photon detection on a chip. Using both numerical and analytical results,
we point out how the quantum Zeno effect may impose fundamental limits on the detection
probability. We discuss possible experimental schemes to realize our proposal.
SFB 631
QIP 2006
Towards Electrical Driven Single Photon Sources Based on Quantum Dots in Photonic Crystal Nanostructures
F. Hofbauer(1), M. Kaniber(1), S. Grimminger(1), G. Böhm(1), S. Dachs(1), M. Bichler(1), G. Abstreiter(1) and J. J. Finley(1)
(1)Walter Schottky Institut, Am Coulombwall 3, 85748 Garching, Germany
We present investigations of electrically tunable InGaAs quantum dots (QDs) coupled to localised optical modes in 2D photonic crystal (PC) nanostructures. The samples consist of a 180
nm thick GaAs p-i-n membrane waveguide into which PCs are formed by etching a triangular
lattice of air holes. Ultra low mode volume nanocavities are formed by introducing reduced
symmetry missing hole defects into the photonic crystal.
The active PC nanocavities were studied using spatially resolved luminescence and photocurrent absorption spectroscopy. Quenching of the PL is observed for fields ¿50 kV/cm due to
carrier tunneling escape from the dots that occurs over timescales faster than the radiative lifetime. By measuring the PL quenching as a function of position on the PC and nanocavity we
electrically probe the local density of photonic states via a shift of the threshold voltage. These
devices have the potential to study cavity-single QD coupling in an electrically tunable system.
2006
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QIP 2006
ESR studies of low energy ion implanted P donors in Silicon
W.D. Hutchison(1), N. Suwuntanasarn(1), P.G. Spizzirri(2), N. Stavrias(2), S.
Prawer(2), J.C. McCallum(2) and E. Gauja(3).
(1) Centre for Quantum Computer Technology, School of PEMS, University of New South
Wales @ ADFA, ACT, 2600 Australia.
(2) Centre for Quantum Computer Technology, School of Physics, University of Melbourne,
Victoria, 3010 Australia.
(3) Centre for Quantum Computer Technology, School of Physics, University of New South
Wales, Sydney 2052 Australia
One method for fabricating silicon based quantum devices (QD) employs low energy ion implantation techniques along with electron beam lithography to accurately position dopant
atoms which, following activation, become the QD qubits. It is common practice to perform
implantation into silicon wafers with a controlled oxide grown on their surface. High quality
oxides exhibit low trap densities in contrast to their native oxide counterparts making them
more suitable for electronic devices. Unfortunately, surface oxides can also be incompatible
with very low energy implantation processes (¡ 10 keV) since they result in reduced dopant
activation due to losses in the surface oxide layer.
In this work, we have studied low energy single and molecular ion implantation, (the latter
as a means of locating donor pairs in close proximity to obtain greater donor wavefunction
overlap). Using the electron spin resonance (ESR) technique, we have monitored the activation
of donors implanted through high quality, thermally grown (5 nm) and native oxides. In addition to donor signals, ESR is also sensitive to the creation of electronic trap states including Pb
centres which arise from silicon dangling bonds at the silicon / silicon oxide interface. The observation of low dopant activation and large Pb signals for this fabrication strategy suggested
that an alternative surface termination may be needed.
SFB 631
QIP 2006
Quantum Phase Transitions in the Bosonic Single-Impurity Anderson Model
H.-J. Lee and R. Bulla
Theoretische Physik III, Elektronische Korrelationen und Magnetismus, Institut fuer Physik,
Universitaet Augsburg
Recently, we generalized the numerical renormalization group method for quantum impurities
coupled to a bosonic bath (1). This method has been shown to give very accurate results for the
spin-boson model.
As another application of the bosonic numerical renormalization group, we investigate the
bosonic single-impurity Anderson model, which is obtained from the standard (fermionic)
single-impurity Anderson model by substituting all fermionic operators with bosonic ones.
Experimentally, one can realize such type of model with an atomic quantum dot in a tight
optical trap which is coupled to a superfluid reservoir via laser transitions (2). Furthermore,
comprehensive knowledge on the impurity model can be extended to the corresponding lattice
system (Bose-Hubbard model) via dynamical mean-field theory.
We found clear evidence of zero-temperature phase transitions for the bosonic single-impurity
Anderson model with sweeping the chemical potential (µ) and the coupling between the dot
and the reservoir (α).
For a finite Coulomb interaction U, the two dimensional phase space (µα-plane) is divided into
the Bose-Einstein condensate phase and the Mott phases with nimp = 0, 1, 2, ... and each phase
boundary shows quantum critical behavior.
[1] R. Bulla, H. J. Lee, N.-H. Tong, M. Vojta, PRB 71, 045122 (2005)
[2] A. Recati, P. O. Fedichev, W. Zwerger, J. von Delft and P. Zoller, PRL 94, 040404 (2005)
2006
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QIP 2006
Decoherence and single electron charging in electronic Mach-Zehnder interferometer
L.V. Litvin, P. Tranitz, W. Wegscheider, and C. Strunk
Institute for experimental and applied physics, University of Regensburg, D-93053 Regensburg,
Germany
We study the temperature and voltage dependence of the quantum interference of single edge
channels in the QHE-regime in an electronic Mach-Zehnder interferometer. The amplitude of
the interference fringes is about 50 times smaller than expected from theory; nevertheless the
decay of the visibility with temperature and applied voltage agrees very well with theoretical
prediction. Superimposed on the Aharonov-Bohm (AB) oscillations, a conductance oscillation
with six times smaller period is observed. The latter depends only on gate voltage and not
on the AB-phase, and can be consistently interpreted as single electron charging of the edge
channels.
SFB 631
QIP 2006
Microwave spectroscopy on Josephson junctions with ferromagnetic barriers
K. Madek(1), M. Weides(2), S. Beutner(1), C. Probst(1), A. Marx(1), and R. Gross(1)
(1)Walther-Meißner-Institut für Tieftemperaturforschung, D-85748 Garching
(2)Institut für Festkörperforschung, Forschungszentrum Jülich
Superconducting qubits are very promising candidates for quantum information processing,
since they are highly decoupled from quasiparticle excitations (superconducting energy gap)
thus allowing for long enough decoherence times. Phase qubits containing a Josephson πjunction have the additional advantage of an intrinsic π-phase shift which leads to a degeneracy point of the qubit at zero applied magnetic flux. Moreover, Josephson π-junctions are
of special interest because until now it is unclear whether they exhibit macroscopic quantum
behavior.
We have performed continuous wave spectroscopy on single Josephson junctions with ferromagnetic barriers of various thickness which hence are either ”0” or ”π”-coupled. Microwave
induced transitions of the phase particle from the ground state to the first excited state by either one or more microwave photons have been observed proving the existence of quantized
energy levels in the potential wells of the junction’s tilted washboard potential and hence the
macroscopic quantum properties of Josephson π-junctions.
2006
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QIP 2006
NRG Matrix Product States and Quantum Information Processing
H. Saberi(1), A. Weichselbaum(1), J. von Delft(1), F. Verstraete(2), and I. Cirac(3)
(1)Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, LudwigMaximilians University of Munich, Munich, Germany,
(2)Institute for Quantum Information, Caltech, Pasadena, US
(3)Max-Planck-Institut für Quantenoptik, Garching, Germany
We use newly developed ”Matrix Product” techniques to compare the Numerical Renormalization Group approach for the Single Impurity Anderson model to the Density Matrix Renormalization Group approach. We would also discuss the prespectives for applying Matrix Product
techniques to time-dependent models relevant for the field of quantum information theory,
such as a qubit coupled to a bath of decohering excitations.
SFB 631
QIP 2006
Kondo conductance in a one electron double quantum dot
D. Schröer(1), A.K. Hüttel(1), K. Eberl(2), S. Ludwig(1), M. Kiselev(3), and B. Altshuler(4)
(1)Center for NanoScience and Sektion Physik, Ludwig-Maximilians-Universität,
Geschwister-Scholl-Platz 1, 80539 München, Germany.
(2)Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany.
(3)Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland,
97074 Würzburg, Germany.
(4)Physics Department, Columbia University, 538 West 120th Street, New York, NY 10027.
We have investigated the Kondo effect in a double quantum dot (DQD) in the few electron
limit. For a charge of just one electron in the DQD, we observe a surprising non-monotonic
dependence of the Kondo current on a perpendicular magnetic field below 50mT. We assign
this behaviour to a magnetic field dependence of the single dot eigen-energies. The alignment
of these states determines the interdot tunnel coupling and, as a consequence, the Kondo current through the serial DQD. Contrariwise, in the two-electron case, transport is determined
by symmetric and anti-symmetric combinations of the wave functions (i.e. singlet and triplet).
Therefore, the two-electron Kondo conductance has little to do with the interdot tunnel coupling and a monotonic magnetic field dependence is oberserved.
The described magnetic field dependent coupling provides an extremely sensitive tool to detect and control the level alignment in a single electron DQD. We consider this an important
step towards the controllable engineering of semiconductor DQD devices, which are promising
candidates for qubits in quantum information processing.
2006
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Phase-space theory for dispersive detectors of superconducting qubits
I. Serban(1), F.K. Wilhelm(1,2)
(1)Ludwig Maximilians Universitaet, Munich, Germany,
(2)University of Waterloo, Waterloo, Canada
Superconducting circuits are envisioned as quantum bits and demonstrate quantum-coherent
features i.e. Rabi oscillations and Ramsey fringes. The detector (e.g. a superconducting
quantum interference device, SQUID) can itself be described by a Hamiltonian and treated
quantum-mechanically.This allows more insights into the measurement process.
Several experimental groups have recently realized good detectors with strong coupling to the
measured system, where nonlinear dynamics plays a significant role.
Motivated by the recent experiment [1], we study a nonlinear detector where the qubit couples
to the square amplitude of a driven oscillator, which can be used for dispersive detection. We
use a complex-environment approach treating the qubit and the oscillator exactly, expressing
their full Floquet-state master equations in phase space. We investigate the backaction of the
environment on the measured qubit and explore the resolution of measurement.
[1] A. Lupaşcu et al. PRL 93 177006 (2004)
SFB 631
QIP 2006
Self-consistent calculation of the electron distribution near a QPC in the presence
of a strong perpendicular magnetic field.
A. Siddiki(1), F. Marquardt(1)
(1) Physics Department, Arnold Sommerfeld center for Theoretical Physics, and CeNS, LudwigMaximillians-Universitaet Muenchen, Germany
The experimental success of developing a ”Quantum Hall” based interferometer, like an optical Mach-Zender interfrometer, has revealed a novel technique to exploit the properties of the
so called ’edge states’ (ES) in the extreme quantum limit [1]. A key element of these experiments are the quantum point contacts (QPCs) and the electrostatic potential (ESP) profile near
these QPCs, that plays an important role in the rearrangement of the ES. The interaction of the
electrons was proposed [1] to be a possible origin of the dephasing and a better understanding requires a self-consistent (SC) calculation of the ESP. Here we present an implementation
of the SC-Thomas-Fermi-Poisson approach [2] to an homogeneous two dimensional electron
system in order to obtain the ESP and electron distribution near the QPC. First the ESP produced inside the semiconductor structure by a QPC placed at the surface is calculated based
on a semi-analytical solution of the Laplace equation [3]. Second, we represent the calculated
ESP distribution by a relatively simple model and calculate the SC (screened) potential together
with the electron densities for finite temperature, magnetic field and gate voltages. We see that
there are three characteristic rearrangement of the incompressible [4] ES, which influences the
current distribution [5].
[1] Nature, 422, 2003, 415
[2] Phys. Rev. B, 50, 1994, 7757
[3] J. Appl. Phys., 77, 1995, 4505
[4] Phys. Rev. B, 46, 1992, 4026
[5] Phys. Rev. B, 70, 2004, 195335
2006
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Indistinguishable Single Photons of Alternating Polarization
H. Specht, T. Wilk, S. Webster, A. Kuhn, G. Rempe
Max-Planck-Institut für Quantenoptik, Garching, Deutschland
We realized a new scheme to generate single photons from an atom-cavity system. A Raman
transition is driven between two Zeeman sublevels of a hyperfine ground state of a single
87 Rb atom. A magnetic field is applied to lift the degeneracy of those levels. A pump laser
drives one branch of the Raman transition while the cavity stimulates the emission of a photon
along the other branch. With every transition a single photon with well defined polarization
is emitted into the cavity. Due to the magnetic splitting Raman resonance for the two possible
directions of the transition is fulfilled for different pump laser frequencies. By alternating the
laser frequency we can drive the process in both directions leading to orthogonal polarizations
of subsequent photons. Their mutual coherence is characterized in a two photon interference
experiment [2], where their suitability for applications in quantum information processing such
as linear optical quantum computing [3] is verified.
[1] Kuhn et al. Phys. Rev. Lett. 89, 67901 (2002)
[2] Legero et al. Phys. Rev. Lett. 93, 070503 (2004)
[3] Knill et al. Nature409, 46 (2001)
SFB 631
QIP 2006
Coupled Josephson Phase Qubits
T. Wirth(1), J. Lisenfeld(1), A. Lukashenko(1), S. Shitov(2), and A.V. Ustinov(1)
(1)Physikalisches Institut III, Universität Erlangen, Germany,
(2)Institute of Radio Engineering and Electronics, Moscow, Russia.
Solid-state quantum bits based on current-biased Josephson junctions have recently been
shown as very promising. They require appropriate isolation from the bias leads which can
be achieved by the use of superconducting transformers. A junction enclosed into a superconducting loop has a double-well potential, where the discrete quantum levels in one well
can be used as qubit states. State-dependent tunneling to the other well changes the magnetic
flux in the qubit, which is measured by a SQUID (Superconducting QUantum Interference
Device). We experimentally demonstrate the preparation of an arbitrary quantum state using
nanosecond long microwave pulses and observe Rabi oscillations using samples fabricated by
a standard foundry. Another crucial point is the coupling of qubits, which we currently study
in a system of two capacitively coupled flux-biased phase qubits. Our ongoing experiments
are focused on spectroscopic measurements of the coupling strength and the demonstration
of coherent interaction in the time domain by observing antiphase oscillation of the two-qubit
states at the degeneracy point.
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List of Participants
79
L IST OF PARTICIPANTS
QIP 2006
Mr. Benjamin Abel
LMU München, ASC and CeNS
Theresienstr. 37
80333 München, Germany
Phone: +49 (0)174 1764218
[email protected]
Prof. Gerhard Abstreiter
Walter Schottky Institut
Technische Universität München
Am Coulombwall
85748 Garching, Germany
Phone: +49 (0)89 2891 2770
[email protected]
Mr. Stefan Ahlers
Am Coulombwall 3
85748 Garching,
Phone: +49 (0)89 289 12736
[email protected]
Dr. Jonathan Baugh
Institute for Quantum Computing
University of Waterloo
200 University Ave W
N2L 6P2 Waterloo, Canada
Phone: +1 519 888 4567 x7491
[email protected]
Mr. Christoph Bihler
Am Coulombwall 3
Phone: +49 (0)89 289 12755
[email protected]
Prof. Immanuel Bloch
Johannes Gutenberg Universität Mainz
Institut für Physik
Staudingerweg 7
55128 Mainz, Germany
Phone: +49 (0)6131 39 26234
[email protected]
Dr. Dominique Bougeard
Am Coulombwall
Phone: +49 89 289 12 777
[email protected]
Dr. Brandt Martin
Am Coulombwall 3
Phone: +49 (0)89 289 12758
[email protected]
Prof. Guido Burkard
Department of Physics and Astronomy
University of Basel
Klingerlbergstrasse 82
CH-4056 Basel, Switzerland
Phone: +41 61 267 3694
[email protected]
Mr. Henning Christ
Max-Planck Institut für Quantenoptik
Hans-Kopfermann-Str. 1
85748 Garching b. Muenchen, Germany
Phone: 089-32905336
[email protected]
Prof. Ignacio Cirac
Max-Planck-Institut für Quantenoptik
Phone: +49 (0)89 32905 736
[email protected]
Ms. Emily Clark
Technische Universitaet Muenchen
Am Coulombwall 3
Phone: +49 (0)89 289 12784
[email protected]
2006
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QIP 2006
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Dr. Gyorgy Csaba
Technical University of Munich
Institute for Nanoelectronics
Arcisstrasse 21
D-80333 München, Germany
Phone: +49 (0)89 289 25339
[email protected]
Ms. Susanne Dachs
Walter Schottky Institute
Technical University of Munich
Am Coulombwall 3
Phone: +49 (0)89 289 12759
[email protected]
Ms. Sonia Dandl
Walther Meissner Institut
Walther-Meissner-Str. 8
Phone: +49 (0)89 3569939
[email protected]
Mr. Frank Deppe
Phone: +49 (0)89 289 14230
[email protected]
Mr. Roland Doll
Universität Augsburg
Universitätsstr. 1
86135 Augsburg, Germany
Phone: +49 (0)821 5983221
[email protected]
Mr. Joerg Ehehalt
Universität Regensburg
Institut für Exp. und Angew. Physik
Lst. Prof. Dr. W. Wegscheider
Universitätsstraße 31
93053 Regensburg, Germany
Phone: +49 (0)941 943 2067
[email protected]
Mr. Olexiy Feofanov
Universitaet Erlangen-Nuernberg
Physikalisches Institut III
Erwin-Rommel-Str. 1
91058 Erlangen, Germany
Phone: +49 (0)9131 8527120
[email protected]
Prof. Jonathan James Finley
Am Coulombwall 3
Phone: +49 (0)89 289 12782
[email protected]
Dr. Anna Fontcuberta i Morral
Technische Universitaet Muenchen
Am coulombwall 3
Phone: +40 (0)89 289 12779
[email protected]
Dr. Jozsef Fortagh
Physikalisches Institut
Universität Tübingen
Auf der Morgenstelle 14
72076 Tübingen, Germany
Phone: +49 (0)7071 29 73033
[email protected]
Dr. Julien Gabelli
Lehrstuhl Prof. Kotthaus
Department für Physik der LMU
München
Geschwister-Scholl-Platz 1
Phone: +49 (0)89 2180 1457
[email protected]
Mr. Thomas Geiger
Physik
Lst. Weiss AG Strunk
Phone: 0941 943 1617
[email protected]
SFB 631
QIP 2006
Prof. Steffen Glaser
TU Muenchen
Chemistry Department
Lichtenbergstrasse 4
Phone: +49 (0)89 289 13759
[email protected]
Dr. Sebastian T.B. Goennenwein
Walther-Meissner-Institut
Phone: +49 (0)89 289 14226
[email protected]
Mr. Benno Grolik
Am Coulombwall 3
Phone: +49 (0)89 289 12730
[email protected]
Prof. Rudolf Gross
Walther-Meissner Str. 8
Phone: +49 (0)89 289 14201
[email protected]
Prof. Dirk Grundler
Physik-Department E10
TU München
James-Franck-Str. 1
Phone: +49 (0)89 289 12401
[email protected]
Mr. Daniel Harbusch
LMU München
LS Kotthaus
Phone: +49 (0)89 2180 5301
[email protected]
Prof. Kees (C.) Harmans
Kavli Institute of NanoScience
Dept. Appl. Physics
Delft Univ. of Technology
POB 5046
2600AG Delft, The Netherlands
Phone: +31 (0)15 2785195
[email protected]
Ms. Theresa Hecht
LMU München
Arnold Sommerfeld Center and CeNS
Theresienstrasse 37
Phone: +49 (0)89 2180 4526
[email protected]
Mr. Tobias Heimbeck
Walther Meissner Strasse 8
Phone: +49 (0)89 289 14224
[email protected]
Mr. Dominik Heiss
Am Coulombwall 3
Phone: +49 (0)89 289 12784
[email protected]
Mr. Ferdinand Helmer
Arnold Sommerfeld Centre for Theoretical
Physics and CENS
LMU München
Theresienstr. 37, 80333 Munich, Germany
Phone: +49 (0)89 2180 4113
[email protected]
Mr. Felix Hofbauer
Am Coulombwall 3
Phone: +49 (0)89 289 12784
[email protected]
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Ms. Susanne Hofmann
Phone: +49 (0)8441 784630
[email protected]
Mr. Hans Huebl
Am Coulombwall 3
Phone: +49 (0)89 289 12768
[email protected]
Dr. Wayne Hutchison
UNSW@ADFA
School of PEMS
2600 Canberra, Australia
Phone: +61 2 6268 8804
[email protected]
Dr. Evgeni Il’ichev
Institute for Physical High Technology
A. Einstein str. 9
07745 Jena, Germany
Phone: +49 (0)3641 206121
[email protected]
Prof. Kohei Itoh
Dept. Applied Physics
Keio University
3-14-1, Hiyoshi, Kohoku-ku
223-8522 Yokohama, Japn
Phone: +81 45 566 1594
[email protected]
Mr. Xiaoyue Jin
Uni Erlangen
Erwin-Rommel-Str. 1
91058 Erlangen, Deutschland
Phone: +49 (0)9131 8527082
[email protected]
Mr. Michael Kaniber
Am Coulombwall 3
Phone: +49 (0)89 289 12784
[email protected]
Prof. Stefan Kehrein
Department für Physik
LMU München
Theresienstr. 37
Phone: +49 (0)89 2180 4539
[email protected]
Dr. Sigmund Kohler
Phone: +49 821 598 3316
[email protected]
Prof. Jörg P. Kotthaus
Center for Nano Science
and Department für Physik
LMU München
Geschwister-Scholl-Platz 1, 80539
München, Germany
Phone: +49 (0)89 2180 3737
[email protected]
Mr. Dawid Kupidura
LMU München
Sektion Physik
LS Kotthaus
Geschwister - Scholl - Platz 1
80539 München, Deutschland
Phone: +49 (0)89 2180 3586
[email protected]
Prof. Dr. Ad Lagendijk
FOM-Institute for Atomic and
Molecular Physics (AMOLF)
Kruislaan 407
1098 SJ Amsterdam, The Netherlands
Phone: +31 (0)20 6081 302
[email protected]
SFB 631
QIP 2006
Prof. Alfred Laubereau
Fakultät für Physik
James-Franck-Straße
85748 Garching bei München, Germany
Phone: +49 (0)89 289 12841
[email protected]
Ms. Hyun-Jung Lee
Theoretische Physik III, EKM
Phone: +49 (0)821 598 3711
[email protected]
Dr. Leonid Litvin
Institute for Experimental and Applied
Physics
Universitaetstrasse 31
D-93053 Regensburg, Germany
Phone: +49 (0)941 943 1620
[email protected]
Dr. Stefan Ludwig
LMU München
Center for Nano Science
and Department für Physik
Phone: +49 (0)89 2180 3733
[email protected]
Mr. Stefan Ludwig
TU München
Am Coulombwall 3
85748 Garching,
Phone: +49 (0)89 289 12784
[email protected]
Mr. Karl Madek
Phone: +49 (0)89 289 14402
[email protected]
Mr. Matteo Mariantoni
Walther-Meissner-Institut (WMI)
Walther-Meissner-Strasse 8
D-85748 Garching b. München, Germany
Phone: +49 (0)89-289-14224
[email protected]
Dr. Florian Marquardt
Sektion Physik
LMU München
(CeNS, ASC)
Theresienstr. 37
Phone: +49 (0)89 21804591
[email protected]
Dr. Achim Marx
Phone: +49 (0)89 289 14211
[email protected]
Mr. Dane Robert McCamey
CQCT, School of Physics
The University of New South Wales
2052 Kensington, Australia
Phone: +61 2 9385 6566
[email protected]
Mr. Edwin Menzel
Phone: +49 (0)89 289 14519
[email protected]
Mr. Joel Moser
Ludwig Maximilians Universität
Department für Physik der LMU
München
80539 Munich, Germany
Phone: +49 (0)89 2180 3349
[email protected]
2006
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86
Prof. Müller Paul
Universität Erlangen-Nürnberg
Erwin-Rommel-Str. 1
91058 Erlangen, Deutschland
Phone: +49 (0)9131 8527272
[email protected]
Mr. Thomas Niemczyk
Phone: +49 (0)89 289 14247
[email protected]
Dr. Matthias Opel
Phone: +49 (0)89 289 14237
[email protected]
Mr. Federico Peretti
TU München
Arcistrasse 21
Phone: +49 (0)89 289 25341
[email protected]
Prof. Gerhard Rempe
85741 Garching bei München, Germany
Phone: +49 (0)89 32905 701
[email protected]
Dr. Stefan Rinner
Lehrstuhl Prof. Dr. K. Richter
Institut fuer Theoretische Physik
Phone: +49 (0)941 943 2020
[email protected]
Mr. Hamed Saberi
Arnold Sommerfeld Center for
Theoretical
Physics , LMU München
Theresienstr. 37
Phone: +49 (0)89 2180 4525
[email protected]
Dr. Andrew Sachrajda
Institute For Microstructural Sciences
National Research Council
M-23a, 1200 Montreal Road
K1K 0H7 Ottawa, Canada
Phone: +1 613-949-0545
[email protected]
Mr. Jürgen Sailer TP C4
Walter Schottky Institute
TU München
Am Coulombwall 3, 85748 Garching,
Germany
Phone: +49 (0)89 289 12736
[email protected]
Mr. Dieter Michael Schlosser
Germany
Phone: +49 (0)89 289 12730
[email protected]
Mr. Daniel Schröer
Department für Physik
LMU München
Phone: +49 (0)89 2180 3738
[email protected]
Dr. Thomas Schulte-Herbrüggen
TU-München
Dept. Chemistry (Prof. Glaser’s group)
Lichtenbergstr. 4
85747 Garching, D
Phone: +49 (0)89 289 13312
[email protected]
SFB 631
QIP 2006
Ms. Ioana Serban
LMU München
Arnold Sommerfeld Center
Theresienstrasse 37
80333 Munich, Germany
Phone: +1-519-888-4567-2825
[email protected]
Dr. Afif Siddiki
Physics Deparment
LMU München
Theresienstr. 37
D-80833 München, Germany
Phone: +49 (0)89 2180 4533
[email protected]
Dr. Jens Siewert
Dipartimento di Metodologie Fisiche e
Chimiche per l’Ingegneria, Universita di
Catania
viale Andrea Doria, 6
95125 Catania, Italy
Phone: +39 095 738 2803
[email protected]
Ms. Johanna Simon
Walter Schottky Institut, E24
TU München
Germany
Phone: +49 (0)89 289 12756
[email protected]
Mr. Narayan Sircar
Walter Schottky Institut, E24
TU München
Germany
Phone: +49 (0)89 289 12717
[email protected]
Mr. Holger Specht
Hans Kopfermann Str. 1
Phone: +49 (0)89 32905333
[email protected]
Prof. Christoph Strunk
Institut für Experimentelle und
Angewandte Physik
Universitätsstr. 31, 93040 Regensburg,
Germany
Phone: +49 (0)941 943 3199
[email protected]
Mr. Stephan Trumm
Physik-Department, E11
James-Franck-Str. 1
85748 Garching b. München, Germany
Phone: +49 (0)89 289 12861
[email protected]
Mr. Xaver Voegele
LMU München
LS Kotthaus
Geschwister Scholl Platz 1, München,
Germany
Phone: +49 (0)89 2180 5301
[email protected]
Prof. Andreas Wallraff
ETH Zurich
Department of Physics
HPF D 14, Schafmattstr. 16
CH-8093 Zurich, Switzerland
Phone: +41 44 633 7563
[email protected]
Mr. Chunlang Wang
Department für Physik, LMU München
Schellingstr.4 / III
Phone: +49 (0)89 2180 5804
[email protected]
Mr. Bernhard Weber
Max-Planck Institut für Quantenoptik
Hans Kopfermann Str. 1
Phone: +49 (0)89 32905398
[email protected]
2006
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88
Prof. Werner Wegscheider
Phone: +49 (0)941 943 2081
[email protected]
Mr. Markus Wesseli
TU München
Physik Department, Lehrstuhl E11
James-Franck-Straße
Phone: +49 (0)89 289 12861
[email protected]
Mr. Georg Wild
Walther-Meißner-Institut
Bayrische Akademie der Wissenschaften
Phone: +49 (0)89 289 14230
[email protected]
Dr. Marc A. Wilde
TU München
Physik-Department E10
James-Franck-Straße 1
85747 Garching , Germany
Phone: +49 (0)40 42838 2932
[email protected]
Prof. Wilhelm Frank
IQC and Physics Department
University of Waterloo
200 University Avenue West
N2L 3G1 Waterloo, ON, Canada
Phone: +1 519 888 4567 X7305
[email protected]
Mr. Tobias Wirth
Universität Erlangen-Nürnberg
Erwin-Rommel-Str. 1
91058 Erlangen, Germany
Phone: +49 (0)9131 8527208
[email protected]
Dr. Martijn Wubs
Universitätsstraße 1
D-86135 Augsburg, Germany
Phone: +49 (0)821 598 3316
[email protected]
Mr. Tobias Zibold
Walter-Schottky-Institut, T33
Am Coulombwall 3
Phone: +49 (0)89 289 12740
[email protected]
Prof. Claus Zimmermann
Physikalisches Institut
Universität Tübingen
Auf der Morgenstelle 14
72076 Tübingen, Germany
Phone: +49 (0)7071 29 76075
[email protected]
SFB 631
Author Index
89
Index
Abdumalikov, A. A., 54
Abel, B., 49
Abstreiter, G., 38, 39, 45, 50, 53, 57, 59
Ahlers, S., 38, 50
Altshuler, B., 65
Arakawa, Y., 45
Böhm, G., 59
Baugh, J., 21
Berroir, J.-M., 44
Beutner, S., 63
Bianchetti, R., 19
Bichler, M., 39, 45, 53, 57, 59
Blais, A., 19
Bloch, I., 23
Bougeard, D., 38, 50
Brandt, M. S., 27
Buehler, T. M., 27
Bulla, R., 61
Burkard, G., 24
Chan, V. C., 27
Chow, J., 19
Christ, H., 33, 51
Cirac, I., 20, 64
Cirac, J. I., 51
Clark, E. C., 45
Clark, R. G., 27
Cory, D. G., 21
Csaba, G., 52
Dachs, S., 59
Dandl, S., 56
Deppe, F., 32
Devitt, S. J., 36
Devoret, M. H., 19
Dzurak, A. S., 27
Eberl, K., 65
Ehehalt, J., 53
Emmert, A., 33
Etienne, B., 44
Fève, G., 44
Fahem, Z., 52
Feofanov, A. K., 54
Ferber, J., 40
Ferguson, A. J., 27
Fink, J., 19
Finley, J. J., 39, 45, 57, 59
Fortagh, J., 29
Fowler, A. G., 36
Frunzio, L., 19
Göppl, M., 56
Gabelli, J., 44
Gambetta, J., 19
Gaudreau, L., 30
Gauja, E., 60
Gennser, U., 44
Gerl, C., 53
Giedke, G., 51
Girvin, S. M., 19
Glaser, S. J., 40, 41
Glattli, D. C., 44
Goeppl, M., 19
Grajcar, M., 18
Greentree, A. D., 36
Grimminger, S., 39, 59
Gross, R., 32, 33, 56, 63
Hänggi, P., 25
Hüttel, A. K., 65
Hackl, A., 37
Hamilton, A. R., 27
Harmans, C., 17
Hawrylak, P., 30
Hecht, T., 55
Heimbeck, T., 56
Heiss, D., 57
Helmer, F., 58
Hofbauer, F., 39, 59
Holleitner, A. W., 43
Hollenberg, L. C. L., 36
Houck, A., 19
91
QIP 2004
92
Huebl, H., 27
Huebner, U., 18
Hutchison, W. D., 27, 60
Meno, T., 32
Meyer, H.-G., 18
Moussa, O., 21
Il’ichev, E., 18
Itoh, K. M., 26
Izmalkov, A., 18
Nakaoka, T., 45
Oliver, W.D., 33
Oreg, Y., 55
Osterloh, A., 35
Jamieson, D. N., 27
Jin, X. Y., 31
Jin, Y., 44
Johnsson, B., 19
Peretti, F., 52
Plaçais, B., 44
Porras, D., 20
Prawer, S., 60
Probst, C., 63
Kakuyanagi, K., 32
Kam, A., 30
Kaniber, M., 39, 59
Karrasch, C., 55
Kayanuma, Y., 25
Kehrein, S., 37
Khaneja, N., 41
Khrapay, V., 42
Kiselev, M., 65
Kohler, S., 25
Korkusinski, M., 30
Kotthaus, J. P., 42
Koval, Y., 31
Krenner, H. J., 45
Kroutvar, M., 57
Kuhn, A., 68
Ramanathan, C., 21
Rebentrost, P., 40
Reilly, D. J., 27
Reinwald, M., 53
Rempe, G., 22, 68
Ryan, C. A., 21
Sabathil, M., 45
Saberi, H., 64
Sachrajda, A. S., 30
Saito, K., 25
Saito, S., 32
Schaeck, S., 57
Scheurer, C., 45
Schoelkopf, R. J., 19
Schröer, D., 65
Schreier, J., 19
Schuh, D., 53
Schulte-Herbrueggen, T., 40, 41
Schuster, D. I., 19
Schuster, R., 53
Semba, K., 32
Serban, I., 66
Shitov, S., 69
Siddiki, A., 67
Siewert, J., 35
Sircar, N., 38, 50
Solano, E., 33, 58
Specht, H., 68
Spizzirri, P. G., 60
Spoerl, A., 40
Spoerl, A. K., 41
Stavrias, N., 60
Storcz, M. J., 40
Laflamme, R., 21
Lagendijk, A., 28
Lapointe, J., 30
Lee, H.-J., 61
Lisenfeld, J., 31, 69
Litvin, L.V., 62
Lohmeyer, R., 35
Ludwig, S., 42, 65
Lugli, P., 52
Lukashenko, A., 31, 69
Müller, P., 31
Madek, K., 56, 63
Majer, J., 19
Mariantoni, M., 33, 58
Marquardt, F., 34, 49, 58, 67
Marx, A., 33, 56, 63
McCallum, J. C., 27, 60
McCamey, D. R., 27
Meden, V., 55
SFB 631
INDEX
INDEX
QIP 2004
Storcz, M.J., 33
Strunk, C., 62
Studenikin, S., 30
Suwuntanasarn, N., 60
Takayanagi, H., 32
Trampert, A., 38, 50
Tranitz, P., 62
Uhlmann, A., 35
Ustinov, A. V., 31, 54, 69
van der Ploeg, S. H. W., 18
Verstraete, F., 64
von Delft, J., 49, 55, 64
Webster, S., 68
Wegscheider, W., 42, 53, 62
Weichselbaum, A., 64
Weides, M., 63
Wellard, C. J., 36
Wilhelm, F. K., 40, 66
Wilhelm, F.K., 33
Wilk, T., 68
Wirth, T., 69
Wubs, M., 25
Yang, C., 27
2006
93
Room Plans
95
2. Floor:
guest rooms 233 – 253
1. Floor:
south wing:
north wing:
staircase to
2. floor
south wing
SR3:
SR4:
SR5:
Bibliothek:
seminar room 3
seminar room 4
seminar room 5
library
guest rooms 101 - 123
north wing
SFB 631
R OOM P LANS
QIP 2004
96
10: large dining room
(Garden Hall)
11: small dining room
(Garden Room)
12: kitchen
13: Forest Hall
1-2: reception
3-8: offices
north wing:
Ground Floor:
2006
south wing
entrance
inner
courtyard
terrace
14
lecture
hall
terrace
lecture hall
seminar room 1
seminar room 2
conference office
meeting room
north wing
14:
SR1:
SR2:
TB:
KR:
R OOM P LANS
QIP 2004
97
Bierstüberl
bar
TV room
club room
skittle alley
leisure room
swimming pool
changing room
sauna
fitness room
table tennis
Basement:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
south wing
SR7:
SR6:
2:
EDV-SR:
seminar room 7
seminar room 6
WEB room
EDV teaching room
north wing
SFB 631
R OOM P LANS
QIP 2004
98

Solid State Based Quantum Information Processing QIP 2006

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