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Calendar of Physics Talks Vienna
| Berufungsvortrag *) - Coherent control of ultracold systems |
| Speaker: | Dr. Christiane Koch (Freie Universität Berlin) |
| Abstract: | Ultracold matter brought quantum effects onto the macroscopic scale, and ultrafast
lasers made quantum dynamical phenomena observable in real-time. Bringing the two
together seems natural and holds the promise of employing quantum interferences in an
unprecedented way. Photoassociation of a molecule from two ultracold atoms provides
an optimal framework for the merger. Combining it with coherent control where the
potential energy surfaces governing the dynamics can be 'shaped', a general route
toward stable ultracold molecules is obtained. The same set of techniques that are
employed to create ultracold molecules via short-pulse photoassociation allow to probe
two-body correlations in ultracold gases. Finally, control of a quantum systems might
need to be restricted to a subspace of the total Hilbert space. This is of particular
relevance for applications in quantum information processing.
*) Professur für Theoretische Physik
(Nichtlineare Dynamik und komplexe Systeme)
|
| Date: | Mon, 16.11.2009 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | TU Wien, Seminarraum 136, 10. Stock, gelber Bereich |
| Contact: | J. Burgdörfer |
| Quantum computer - dream and realization |
| Speaker: | Rainer Blatt (Institute for Experimental Physics, University of Innsbruck and Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences) |
| Abstract: | Computational operations always rely on real physical processes, which are data input, data representation in a memory, data manipulation using algorithms and finally, the data output. With conventional computers all the processes are classical processes and can be described accordingly. It is known for several years now that certain computations could be processed much more efficiently using quantum mechanical operations. Therefore, there it would be desirable to build a quantum computer. This requires the implementation of quantum bits (qubits), quantum registers and quantum gates and the development of quantum algorithms. In this talk, several techniques for the implementation of a quantum computer will be briefly reviewed. In particular, the trapped-ion approach will be highlighted in detail and experimental realizations of quantum registers and quantum gate operations using strings of trapped ions in a linear Paul trap will be discussed. With a small ion-trap quantum computer based on up to eight trapped Ca+ ions as qubits we have generated in a pre-programmed way specific quantum states. In particular, entangled states such as Bell states, GHZ and W states, were generated deterministically using an algorithmic procedure. With a tomographic method, these states were subsequently analysed and the respective entanglement was characterized. With Bell states as a resource, entangled states were applied for teleportation and improved precision measurements. |
| Date: | Mon, 16.11.2009 |
| Time: | 17:30 |
| Location: | TU Wien, Freihaus, Hörsaal 5 (2. Stock, grüner Bereich), Wiedner Hauptstr. 8-10, 1040 Wien |
| Contact: | Prof. J. Schmiedmayer |
| Vienna Theory Lunch Club - Type II String Vacua and Phenomenology |
| Speaker: | Ching-Ming Chen (TU Vienna) |
| Abstract: | The goal of string phenomenology is to find a convincing connection between realistic particle physics and string theory. Type II compactifications involving D-branes have been studied recently. Gauge groups are from D-brane stacks and chiral fermions arise from strings stretching between D-branes intersecting at angles (Type IIA) and in its T-dual (Type IIB) picture with magnetized D-branes. Fluxes introduced in model building can stabilize the undetermined dilaton, complex, and Kaehler moduli in different vacua. So far several semi-realistic Pati-Salam and GUT models have been constructed in Minkowski and AdS vacua. A particular D-brane model is chosen to explore its phenomenology. It is also possible to generically study the soft supersymmetry breaking terms, from which can be calculated the supersymmetric partner spectra from supergravity parameters. Fermion masses and mixings can be controlled by the three- and four-point functions using Yukawa couplings which arise from the string worldsheet instantons.
Overview Lunch Seminar |
| Date: | Tue, 17.11.2009 |
| Time: | 12:30 |
| Duration: | 60 min |
| Location: | TU Vienna, Inst. f. Theoretical Physics, Freihaus, Wiedner Hauptstr. 8-10, 10. OG, SEM136 |
| Contact: | Maximilian Attems, David Burke, Marcus Huber, Theo Adaktylos |
| The Search for Superhard Materials: Go Nano! |
| Speaker: | Prof. Dr. Dr. h.c. Stan Veprek (Department of Chemistry, Technical University Munich, Garching/D) |
| Abstract: | Intrinsically super- (H ≥ 40 GPa) and ultrahard (H ≥ 80 GPa) materials attain high hardness from their large intrinsic strength, whereas extrinsically super- and ultrahard materials reach such hardness due to their nanostructure [1]. I shall discuss examples of bulk materials with high elastic moduli but relatively low hardness, because, upon shear strain, the materials undergo instability of the electronic structure and softening. Afterwards, I'll concentrate on the understanding of the origin of ultrahardness in nc-TiN/a-Si3N4 and related nanocomposites, in which 3-4 nm small TiN nanocrystals are “glued” together by about 1 monolayer thick SiNx interface, that is strengthened by enhanced valence charge density. Ab initio DFT calculation of the shear strength of the interfaces, Sachs averaging, pressure enhancement of the flow stress and Tabor’s relation between the hardness H and yield strength Y, H ≈ 2.84∙Y, explain why these materials can reach hardness significantly larger than diamond [2]. The charge transfer to the SiNx interface induces Friedel oscillations of the valence charge density causing that ideal shear and decohesion to occur within the TiN nanocrystals but not in the SiNxinterface [3]. Non-linear finite element modelling explains the unusual combination of mechanical properties of these materials [4]. Present industrial applications will be briefly discussed [5].
[1] S. Veprek, J. Vac. Sci. Technol. A 17 (1999) 2401
[2] S. Veprek et al., Phil. Mag. Lett. 87 (2007) 955.
[3] R. F. Zhang et al., Phys. Rev. Lett. 102 (2009) 015503; Phys. Rev. B 79 (2009) 245426.
[4] M. G. J. Veprek-Heijman et al., Surf. Coat. Technol. 203 (2009) 3385.
[5] S. Veprek and M. G. J. Veprek-Heijman, Surf. Coat. Technol. 202 (2008) 5063. |
| Date: | Tue, 17.11.2009 |
| Time: | 16:00 |
| Location: | Technische Universität Wien, Institut für Allgemeine Physik, Seminarraum 134A, Turm B (gelbe Leitfarbe), 5. OG, 1040 Wien, Wiedner Hauptstraße 8-10 |
| Contact: | Ao.Univ.Prof. Dr. Herbert Störi |
| Kaon Decays in Chiral Perturbation Theory |
| Speaker: | Gerhard Ecker (Univ. Wien) (Fakultät für Physik) |
| Abstract: | im Rahmen des Teilchenphysikseminars |
| Date: | Tue, 17.11.2009 |
| Time: | 16:15 |
| Duration: | 60 min |
| Location: | Erwin Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock |
| Contact: | H. Neufeld |
| Chemisch-Physikalische Gesellschaft - Nanomaterials in the new light: Scattering experiments with synchrotron radiation and neutrons. |
| Speaker: | Oskar Paris (Institut für Physik, Montanuniversität Leoben ) |
| Abstract: | Vortrag im Rahmen der Chemisch-Physikalischen Gesellschaft. |
| Date: | Tue, 17.11.2009 |
| Time: | 17:00 |
| Location: | Lise-Meitner-Hörsaal, Fakultät für Physik, Universität Wien, 1090 Wien, Strudlhofgasse 4/Boltzmanngasse 5, 1. Stock. |
| Contact: | Christl Langstadlinger |
| Berufungsvortrag *) - Nonlinear waves in periodic and disordered structures |
| Speaker: | Sergej Flach (Max-Planck-Institut für Physik, Dresden) |
| Abstract: | Wave propagation and localization in structured systems is strongly influenced by the
presence of nonlinearities, i.e. wave-wave interactions. In the absence of spatial disorder, linear wave
equations yield ballistic spreading of localized excitations. Strong enough wave-wave interaction leads
to an off-resonance stabilization of the initial excitation and the formation of localized states-discrete
breathers. These states have been observed e.g. in Bose-Einstein condensates in optical lattices,
Josephson junction and optical waveguide networks, antiferromagnets and atomic vibrations in
crystals.Adding spatial disorder induces Anderson localization for noninteracting waves, as recently
observed for Bose-Einstein condensates and optical waveguide networks.The combined influence of
disorder and wave-wave interactions has been questioned since half a century.I will present fresh
results which show that weak wave-wave interaction induces weak chaos, destroys Anderson
localization, and leads to universal spreading features of wave packets
*) Professur für Theoretische Physik
(Nichtlineare Dynamik und komplexe Systeme)
|
| Date: | Wed, 18.11.2009 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | TU Wien, Seminarraum 134, 5. Stock, gelber Bereich |
| Contact: | J. Burgdörfer |
| Berufungsvortrag *) - Quantum transport in complex finite systems |
| Speaker: | Sandro Wimberger (Universität Heidelberg) |
| Abstract: | Modern quantum optical and atomic physics experiments allow for
an unprecedented control of microscopic degrees of freedom, not just in the
initialization but, more importantly, in the dynamical evolution of quantum states.
Our goal is to efficiently describe quantum transport phenomena in experimentally
accessible complex systems. Complexity may arise from external driving forces like
for driven single-electron Rydberg states or for kicked cold atoms, or/and from
particle-particle interactions as present in ultracold quantum gases. The theoretical
modelling and understanding of ionisation and transport processes is the necessary
prerequisite for coherently controlling such complex quantum systems.
*) Professur für Theoretische Physik
(Nichtlineare Dynamik und komplexe Systeme)
|
| Date: | Thu, 19.11.2009 |
| Time: | 16:00 |
| Duration: | 60 min |
| Location: | TU Wien, Seminarraum 134, 5. Stock, gelber Bereich |
| Contact: | J. Burgdörfer |
| Berufungsvortrag *) - Lasing in complex photonic media |
| Speaker: | Hakan Türeci (ETH Zürich) |
| Abstract: | In my talk, I will describe an 'ab initio' self-consistent (AISC) approach to access
the steady state properties (frequencies, thresholds, internal and external fields) of an arbitrarily
complex laser structure from a few simple inputs of the resonator and the gain medium. This
approach overcomes two of the essential obstacles faced by time-independent approaches: the
correct description of an arbitrary degree of leakiness of the light-confining structure and the
spatial hole-burning interactions in the multi-mode regime. It does so by introducing an
appropriate set of modes, namely the set of "Constant Flux Modes", to correctly describe the
steady state response of the linear scattering system and a self-consistent set of equations to treat
the lasing non-linearity in the multi-mode regime to infinite order. The lasing properties of
diffusive random lasers, a case that presented a formidable challenge to conventional laser theory
was recently addressed using the AISC theory successfully (Science 320, 643, 2008). I will present
a brief sketch of the basic framework of AISC and a few representative applications to design of
power-efficient and functional micro and nano-lasers.
*) Professur für Theoretische Physik
(Nichtlineare Dynamik und komplexe Systeme)
|
| Date: | Fri, 20.11.2009 |
| Time: | 09:00 |
| Duration: | 60 min |
| Location: | TU Wien, Seminarraum 134, 5. Stock, gelber Bereich |
| Contact: | J. Burgdörfer |
| FAST - Femtosecond-Attosecond Science Technology: Manipulating Electrons with Lasers |
| Speaker: | André D. Bandrauk, Université de Sherbrooke, Québec, Canada (ADLIS Seminar) |
| Date: | Fri, 20.11.2009 |
| Time: | 14:00 |
| Duration: | 60 min |
| Location: | Seminarraum CBEG02, Institut f. Photonik, Gußhausstr. 27 |
| Contact: | SFB ADLIS Sekretariat, Heike Höller, 58801 13625 |
| Nanomechanical measurements of a superconducting qubit |
| Speaker: | Matt LaHaye (Syracuse University, New York) |
| Abstract: | There is a rapidly growing effort to integrate quantum technologies with mechanical systems in order to reach the quantum limits of force and position detection and also to study fundamental issues in quantum mechanics such as the quantum-to-classical transition. One promising approach that has received extensive theoretical attention in recent years is to incorporate superconducting qubits as control and detection elements in nano- electromechanical systems (NEMS). Proposals in the literature posit the qubits as veritable toolboxes for preparing, manipulating and measuring quantum states of a nanomechanical resonator, including Fock states and superposition states. In an initial step toward implementing these advanced strategies, we have performed the first measurements of a nanomechanical resonator coupled to a superconducting qubit, the Cooper-pair box (CPB). We find that the coupling produces a CPB-state-dependent shift in the frequency of the nanoresonator that is similar to the single-atom phase shifts experienced by electromagnetic resonators in the dispersive limit of cavity quantum electrodynamics (CQED). In my talk, I will report on our latest measurements of the dispersive interaction between a CPB and nanoresonator, including how we use the nanomechanical frequency shift to perform spectroscopy and read-out quantum interference effects in the CPB. I will also discuss the realistic prospects of soon using qubit-coupled NEMS for exploring the quantum limit of nanomechanics. |
| Date: | Fri, 20.11.2009 |
| Time: | 15:15 |
| Duration: | 45 min |
| Location: | Seminarraum des Atominstituts, Stadionallee 2 |
| Contact: | Johannes Majer |
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