CPT

Calendar of Physics Talks Vienna

Exploring topological states with cold atoms and photons
Speaker:Eugene Demler (Harvard University)
Abstract:I will review recent theoretical ideas and experimental realizations of topological states using ultracold atoms in optical lattices and quantum walk protocols with photons. Such systems enabled several types of measurements, which had not been possible in solid state systems, including direct measurements of the Berry/Zak phases of Bloch bands and observation of edge states on domain walls in the one dimensional SSH model. I will also discuss new types of topological states in periodically modulated Floquet-Bloch bands which have been realized in photon quantum walks.
Date: Mon, 08.10.2012
Time: 17:30
Duration: 60 min
Location:Univ. of Vienna, Christian Doppler Hörsaal, Boltzmanngasse 5, 3rd floor, 1090 Wien
Contact:Dr. Christiane Losert / Univ. of Vienna

Verschleißmessung im Nanometerbereich basierend auf Radioaktive Isotopen
Speaker:Dr. Martin Jech (AC2T, Wr. Neustadt)
Abstract:Aufgrund von typischen Einschränkungen in der Zugänglichkeit von tribologischen Kontakten sind viele Messprinzipien kaum in der Lage, Verschleiß vor allem im Submikrometerbereich zu detektieren. Die Verwendung von radioaktiven Isotopen erweist sich dabei als eine mögliche und mit vertretbarem Aufwand realisierbare Methode. Die erreichbare Auflösung bei Verschleißmessung mit radioaktiven Isotopen steigt in erster Linie mit der eingesetzten Aktivität. Dies wird allerdings durch die Sicherheitsbestimmungen hinsichtlich der gesundheitlichen Risiken und Handhabung für radioaktive Stoffe limitiert. Als Ziel für die Verbesserung einer solchen Verschleißmessmethode für den Einsatz bei Komponenten- und Modelltests in einer normalen Laborumgebung kann daher die Verknüpfung zwischen hoher Auflösung und geringer Aktivität gesehen werden. Die Umsetzung des entsprechenden Messkonzeptes im Rahmen der g
Date: Tue, 09.10.2012
Time: 16:00
Location:Technische Universität Wien, Institut für Angewandte Physik, Seminarraum 134A, Turm B (gelbe Leitfarbe), 5. OG, 1040 Wien, Wiedner Hauptstraße 8-10
Contact:Ao.Univ.Prof. Dr. Herbert Störi

Manipulation and detection of local and non-local entanglement with quantum dots
Speaker:Seigo TARUCHA (Department of Applied Physics, The University of Tokyo))
Abstract:Manipulation of quantum entanglement is the core of quantum computation and has recently been implemented in solid state systems for spins and superconducting Josephson junctions. The local entanglement is typically the case for spin singlet states, and its manipulation enables to prepare universal sets of logical gates in quantum computing. We have recently used a two qubit gate of combined spin rotation and spin exchange coupling to control spin entanglement in double quantum dots [1]. On the other hand, the concept of non-local entanglement is well established for correlated photon pairs but not yet for solid state systems because of the strong interaction with environment. We have recently proposed new schemes of manipulating and detecting non-local entanglement using a technique of surface acoustic wave (SAW) and quantum dot Josephson junctions. In this talk I will review the schemes of manipulating local and non-local spin entanglement with quantum dots. We previously demonstrated that an electron can be trapped and moved by a SAW burst from one dot to another [2]. This SAW technique can also be used to transfer two electrons or singlet pair through a quantum wire and separate them into two branches of an AB ring connected to the wire. The entanglement may be maintained for the split electrons in the AB ring if the transport through the system is phase coherent [3]. In addition, we have recently prepared a Josephson junction including single InAs quantum dots to observe the Josephson current significantly depending on the charge state because the pair tunneling or local Josephson current is strongly influenced by Coulomb blockade effect [4]. Now we use a similar Josephson junction but including two parallel coupled InAs quantum dots to study the non-local Josephson current, which may be larger than the local Josephson current. We observe the supercurrent depending on the double dot charge state and discuss the contribution from the split Cooper pair tunneling through two separate dots as a non-local process. [1] R. Brunner, Y.-S. Shin, T. Obata, Y. Tokura, M. Pioro-Ladrière,T. Kubo,T. Taniyama, and S. Tarucha, Phys. Rev. Lett. 107, 146801 (2011). [2] S. Hermelin, S. Takada, M.Yamamoto, S. Tarucha, A.D. Wieck, L. Saminadayar, C. Bäuerle, and T. Meunier, Nature 477, 435 (2011). [3] M. Yamamoto, S. Takada, C. Bäuerle, K. Watanabe, A.D.Wieck, and S. Tarucha, Nature Nano. 7, 247 (2012). [4] Y. Kanai, R. S. Deacon, A. Oiwa, K. Yoshida, K. Shibata, K. Hirakawa, and S. Tarucha, Appl. Phys. Lett. 100, 202109 (2012).
Date: Wed, 10.10.2012
Time: 17:30
Location:Universität Wien, Lise-Meitner-Hörsaal, Strudlhofg. 4, 1090 Wien
Contact:J. Schmiedmayer

The road to unbounded complexity.The case of human language and other (non) related issues
Speaker:Bernat Corominas-Murtra (Mediz.Univ.Wien)
Abstract:im Rahmen der gemeinsam veranstalteten Seminare "Komplexe Stochastische Systeme" (Univ.Wien) und "Analyse Komplexer Systeme" (Mediz.Univ.Wien)
Date: Fri, 12.10.2012
Time: 14:15
Duration: 90 min
Location:Medizinische Universität Wien, Informatikbibliothek Bauteil 86, E 03, Spitalgasse 23
Contact:H. Hüffel, Stefan Thurner