# Calendar of Physics Talks Vienna

 Quantum Theseus beats the Minotaur faster
 Speaker: Yasser Omar (University of Lisbon) Abstract: Quantum computers can offer a speed-up for the spatial search problem, namely to find a marked vertex in a given graph. In particular, as defined by Childs and Goldstone, it is possible to perform quantum spatial search using a continuous-time quantum walk. Until recently, this approach was known to yield the optimal quadratic speed-up only for a handful of graphs, where symmetry and regularity seemed to be key features. However, in a sequence of works together with A. Ambainis, M. Mohseni, H. Neven, L. Novo, and S. Chakraborty, we have shown that quantum spatial search by quantum walk is robust to the loss of edges in a graph, and is in fact optimal for almost all graphs. Furthermore, I will show how these results on search can be extended to establish high fidelity quantum communication between two arbitrary nodes of a random network of interacting qubits, namely to perform quantum sta Date: Mon, 20.06.2016 Time: 17:30 Duration: 60 min Location: ATI, Stadionallee 2, Lecture-Hall, Vienna Contact: www.coqus.at / Christina Becker

 Loop functions in thermal QCD
 Speaker: Antonio Vairo (TU München) Abstract: im Rahmen des Teilchenphysikseminars: We present recent computations of loop functions in thermal QCD like the Polyakov loop, the Polyakov loop correlator and the cyclic Wilson loop. We discuss divergences and how to renormalize them. Finally we compare with lattice data. Date: Tue, 21.06.2016 Time: 16:15 Duration: 60 min Location: Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock Contact: A. Hoang, Y. Wang

 Quantum Tests of Gravity
 Speaker: Markus Aspelmeyer (Univ. Wien) Abstract: This is an overview talk on the topic. It starts with the early pioneering experiments by Pound and Rebka and by Colella, Overhauser and Werner that demonstrate the effect of the gravitational potential on the frequency of a photon and on quantum interference fringes in a neutron interferometer, respectively. The latter represents the first experiment that required the use of both Planck’s constant and Newton’s constant (via earth’s acceleration g) to describe the observed interference fringes. Over the following decades, modern quantum physics added new tools and allowed to significantly expand the available quantum experiments that test the effects of weak gravitational fields, including atomic fountains (pioneered by Kasevich and Chu), lab-¬‐based atomic clock tests of the gravitational red shift or the demonstration of gravitationally bound states of cold neutrons. . . . . . Date: Thu, 23.06.2016 Time: 12:30 Duration: 60 min Location: Arbeitsgruppe Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock, 1090 Wien Contact: P.T. Chrusciel

 Smooth conformal Einstein-lambda-dust flows across time-like infinity
 Speaker: Helmut Friedrich (MPI Golm) Abstract: We consider the Einstein-dust equations with positive cosmological constant $\lambda$ onmanifolds with time slices diffeomorphic to an orientable, compact 3-manifold $S$. It is shown that the set of standard Cauchy data for the Einstein-$\lambda$-dust equations on $S$ contains an open (in terms of suitable Sobolev norms) subset of data which develop into solutions that admit at future time-like infinity a space-like conformal boundary ${\cal J}^+$ that is $C^{\infty}$ if the data are of class $C^{\infty}$ and of correspondingly lower smoothness otherwise. The class of solutions considered here comprises non-linear perturbations of FLRW solutions as very special cases. It can conveniently be characterized in terms of asymptotic end data induced on ${\cal J}^+$. These data must only satisfy a linear differential equation. .... Date: Thu, 23.06.2016 Time: 14:00 Duration: 60 min Location: Arbeitsgruppe Gravitation, Währinger Strasse 17, Seminarraum A, 2. Stock, 1090 Wien Contact: P.T. Chrusciel

 Non-relativistic limits of relativistic (super-)gravity
 Speaker: Jan Rosseel (U. Bern) Date: Thu, 23.06.2016 Time: 14:15 Duration: 60 min Location: SEM 136, TU Wien, Freihaus, 10th floor (Wiedner Hauptstr. 8-10, A-1040 Vienna) Contact: Daniel Grumiller

 Mixed surface oxides on rutile TiO2(011) & One-dimensional electron systems in grain boundaries of MoSe2
 Speaker: Matthias Batzill (Department of Physics, University of South Florida, Tampa, FL 33620, USA) Abstract: Materials with reduced dimensions, i.e. two- or one-dimensional, often exhibit unique structural, chemical, and electronic properties compared to bulk (3D) materials. Here I will discuss two quite diverse systems. One system is the 2D mixed surface oxide on a bulk rutile TiO2(011) surface. In particular we investigate the formation of intermixed FeO/TiO2(011) and VOx/TiO2(011) surfaces. These surfaces form complex mixed oxides without bulk counterparts and may give insight on interfaces of oxide heterostructures or surface properties of mixed oxides. The other system is the twin grain boundary in MoSe2. These boundaries form during van der Waals epitaxy of MoSe2 on MoS2 or HOPG substrates. A high density and crystallographical alignment enables angle resolved photoemission (ARPES) electronic structure characterization on crystal-defects for the first time. We demonstrate that these line Date: Thu, 23.06.2016 Time: 16:00 Location: yellow tower „B“, 2th floor, lecture room FH Hörsaal 2 (room number DB02O23), 1040 Wien, Wiedner Hauptstraße 8-10 Contact: Univ.Prof. Dr. Ulrike Diebold

 Circuit Nano-Electromechanics
 Speaker: Hans Hübl (Walther-Meißner-Institut , Garching, Deutschland) Abstract: Micro- and nanomechanical elements are extensively studied due to their importance in force and mass sensing applications. To access their mechanical response, these vibrating elements are typically integrated into an electronic, electromagnetic, or optical environment. In cavity optomechanics, the interaction of a light field in an optical resonator with the mechanical degree of freedom goes beyond the sole readout functionality. Here, the light-matter interaction enables the manipulation of the mechanical state, manifesting itself e.g. in the form of a damped and amplified the mechanical motion [1]. This coupling concept can be straightforwardly transferred from the optical to the microwave (MW) regime defining the sub-field of circuit nano-electromechanics. Moreover, quantum information processing based on superconducting circuits is also at home in this frequency domain. Therefore, nano-electromechanics and superconducting quantum circuits use compatible technologies. This paves the way for true hybrid quantum nano-electromechanical systems that enable the investigation of quantum mechanics in the literal sense. In my talk, I present a mechanical sensing approach for the investigation of solid-state properties in nano-sized systems, show implementations and consequences of the light-matter interaction in circuit nano-electromechanical systems, and discuss the physics of a hybrid combining superconducting quantum circuits with nanomechanical elements. Date: Fri, 24.06.2016 Time: 15:30 Location: Atominstitut, Hörsaal, Stadionallee 2, Wien 2 Contact: J. Majer

 How far we have advanced from the Abrikosov vortices
 Speaker: Prof. Mikhail A. Shifman (Univ. of Minnesota) Abstract: In the early 1950s, Alexei Abrikosov predicted superconductors of the second kind and demonstrated that external magnetic fields should generate vortices (magnetic flux tubes) in the bulk of the superconducting sample. This was the first example of topological solitons in quantum field theory. In the mid-1970s, Nambu, 't Hooft and Mandelstam conjectured that the dual Meissner effect and formation of chromoelectric vortex lines were resonsible for quark (color) confinement at strong coupling. The second coming of the topological vortex strings occurred with the advancement of supersymmetry. In 1994 Seiberg and Witten analytically proved the dual Meissner effect in a supersymmetric Yang-Mills theory with parallels in QCD. In 2003 the so-called non-Abelian vortex flux tubes were constructed, also in a supersymmetric setting. . . . . . Date: Fri, 24.06.2016 Time: 16:15 Duration: 90 min Location: Fakultät für Physik, Erwin-Schrödinger-Hörsaal, Boltzmanngasse 5, 5. Stock Contact: G. Ecker, A. Hoang, H. Neufeld