Calendar of Physics Talks Vienna

Quantum Information Processing with Finite Thermodynamic Resources (Vienna Theory Lunch Seminar)
Speaker: Jake Xuereb (TU Wien)
Abstract:Rolf Landauer once remarked “Information is not an abstract entity but exists only through a physical representation, thus tying it to all the restrictions and possibilities of our real physical universe.” In this talk I will review how this thought manifests itself in various ways in quantum information processing. To begin with, keeping track of the passage of time requires the production of entropy and any unitary is generated by Hamiltonian which is enacted by an agent for some time. So how does an agent's ability to keep time impact their ability to carry out quantum computation? In [1] we make use of ideas from the field of quantum clocks to bound the achievable fidelity of a class of quantum circuits depending on their circuit complexity and the quality of the clock the agent has access to. [..] [[part of the "Vienna Theory Lunch Seminar, see https://lunch-seminar.univie.ac.at ]]
Date: Tue, 16.01.2024
Time: 12:30
Duration: 75 min
Location:University of Vienna, Boltzmanngasse 5, 5th floor, Schrödinger Lecture Hall
Contact:Florian Lindenbauer

Probing the asymptotic structure of 4d Einstein gravity: flat from AdS
Speaker:Matthieu Vilatte (Ecole Polytechnique, Paris & Aristotle University of Thessaloniki)
Abstract:My talk will focus on the structure of gravity at large distances and especially on how one can get insights on the asymptotically flat structure from the one of Anti-de Sitter spacetimes. I will start by recalling some basics on the gauge fixing approach to the IR structure of gravity, insisting on the fundamental examples of the Fefferman-Graham and Bondi gauges and on asymptotically AdS and flat spacetimes. As Ricci flat solutions are usually obtained from a the \Lambda -> 0 limit of Einstein’s spacetimes, I will describe how one can get the flat solution space and flux/balance equations from a careful Laurent expansion of the AdS energy-momentum tensor and the requirement of the line-element finiteness, the analysis being conducted in a covariant version of the Newman-Unti gauge that will be presented prior to these developments.
Date: Tue, 16.01.2024
Time: 14:00
Duration: 60 min
Location:Erwin Schroedinger-Hoersaal (Boltzmanngasse 5, 5th floor)
Contact:Adrien Fiorucci, Daniel Grumiller

Shooting molecular movies of gaseous molecules with a reaction microscope and a high-repetition-rate soft X-ray FEL
Speaker:Florian Trinter (Molecular Physics, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin/Germany)
Abstract:Following chemical reactions and structural changes in molecules in real time has been a long-standing dream in physical chemistry. Accordingly, time-resolved single-molecule imaging has been one central aim triggering the development of x-ray free-electron lasers (XFELs). With the advent of XFELs, corresponding studies in the gas phase came into reach. The high repetition rate of the European XFEL finally opens the door to coincidence experiments and the talk will present the successful implementation of this technique using a COLTRIMS reaction microscope at the European XFEL. For example, our experiments demonstrate that photoelectron diffraction imaging of a molecular breakup is finally possible using high-repetition-rate XFELs [1]. Furthermore, molecular-frame photoelectron angular distributions upon double core-hole generation [2] as well as charge-up and fragmentation dynamics afte
Date: Tue, 16.01.2024
Time: 16:00
Location:TU Wien, Institut für Angewandte Physik, E134 1040 Wien, Wiedner Hauptstraße 8-10 Yellow Tower „B“, 5th floor, SEM.R. DB gelb 05 B
Contact:Prof.Dr. Richard Wilhelm

Revisiting strong-coupling determinations from event shapes
Speaker: Guido Bell (University of Siegen)
Abstract:Electron-positron event shapes are among the oldest and most established observables for extracting the strong coupling constant. The most precise determinations based on the thrust and C-parameter distributions yielded values, however, that are currently in tension with the PDG world average. We therefore revisited the theoretical foundation of the event-shape fits, in particular their implementation of non-perturbative effects. Interestingly, we found that the combined effect of altering the renormalon subtraction scheme and perturbative scale parameters can lead to a few-percent-level impacts on the extracted alpha_s value, indicating a potentially important systematic theory uncertainty that should be accounted for.
Date: Tue, 16.01.2024
Time: 16:15
Duration: 60 min
Location:Fakultaet fuer Physik, Erwin-Schroedinger-HS, Boltzmanngasse 5, 5. Stock
Contact:A. Hoang, M. Procura

(CANCELLED!) Dynamics of nonlinear scalar field with Robin boundary condition on the Schwarzschild--Anti-de Sitter background
Speaker:Maciej Maliborski (U of Vienna)
Abstract:We study the dynamics of a self-interacting spherically symmetric scalar field propagating on the Schwarzschild-anti-de Sitter background. We consider two parameters in the model: the size of the black hole and the Robin boundary parameter. In addition, we study both the focusing and defocusing nonlinearities. We find a pitchfork bifurcation in the defocusing case and for the focusing nonlinearity, a region of the phase space where all solutions blow up in finite time. An extensive study of static solutions and their linear stability allows us to provide a precise asymptotic description of global-in-time solutions and solutions near the threshold of finite-time blowup. This work is a first step in extending https://arxiv.org/abs/2001.03980 to asymptotically anti-de Sitter black hole spacetimes.
Date: Wed, 17.01.2024
Time: 14:15
Duration: 60 min
Location:Seminarraum A, Waehringer Strasse 17, 2nd Floor
Contact:P. Chrusciel

Towards atom-cavity coupling for engineering entanglement
Speaker: Stephan Roschinski (TU Wien, Atominstitut)
Abstract:The efficient and deterministic generation of entanglement in a many-body system poses a challenge for analog and digital quantum simulators. While atomic platforms provide great scalability, they mostly rely on local couplings, for instance, collisional or Rydberg interactions, which can be detrimental for quantum algorithms or quantum simulations of models involving long-range interactions. A promising approach to realize non-local couplings are light-induced interactions by strongly coupling the atoms to an optical cavity, but this has not been achieved yet. We are currently building a new experimental apparatus to strongly couple an atomic tweezer array to a fiber-based Fabry-Pérot cavity. The setup is optimized for repetition rates of several Hz. The starting point is a laser cooled-atomic cloud, which we load within about 100ms despite using an asymmetric beam configuration that
Date: Wed, 17.01.2024
Time: 16:15
Duration: 45 min
Location:Helmut Rauch Hörsaal ATI
Contact:Maximilian Prüfer

Conformal Carrollian scalars and their holographic realisations
Speaker:Simon Pekar (Ecole Polytechnique)
Abstract:Motivated by the extension of the AdS/CFT correspondence to asymptotically flat space-times and in particular the Carrollian approach to flat-space holography, I will present a holographic realisation of conformal (massless) Carrollian scalar field theories, seen as boundary degrees of freedom living on the null infinity of Minkowski space-time. I will present both the electric and magnetic theories, with a particular emphasis on their symmetries. This analysis may serve as a first step towards establishing a holographic dictionary, and I will argue that both theories are crucial in the study of flat-space higher-spin holography.
Date: Thu, 18.01.2024
Time: 17:00
Duration: 60 min
Location:TU Wien, Freihaus, Seminar room 10th floor
Contact:Iva Lovrekovic, Adrien Fiorucci

Coherence and statistics of light from ensembles of many independent single photon emitters
Speaker:Lukáš Slodička (University of Olomouc)
Abstract:We present realizations of several regimes of free-space optical emission of light from large trapped ion crystals, which result in different paradigmatic regimes of photon statistics, including pure single photons or the largest discrete photonic nonclassical states [1]. We provide experimental evidence of single-modeness and phase coherence for light scattered from many ions [2], which correspond to crucial ingredients for the efficient photonic generation of atomic entanglement, or for the directional control of optical emission from atoms [3]. The achieved excitation and detection regimes provide the demonstration of the emergence of super-Poissonian quantum statistics from a finite number of indistinguishable single-photon emitters [4] and enable significant enhancement of collection efficiency of nonclassical light scattered from ion strings in linear Paul traps. [1] P. Obsil et al
Date: Fri, 19.01.2024
Time: 10:00
Duration: 45 min
Location:Helmut Rauch Hörsaal ATI
Contact:Tomas Sikorsky

Toward collective dissipation in arrays of dysprosium atoms
Speaker:Britton Hofer (Institut d’Optique)
Abstract:Controlling the collective dissipation in an ensemble of atoms holds exciting perspectives for future quantum technology applications. We propose to create subradiant modes in sub-lambda arrays of dysprosium atoms. In fact, interest in using lanthanide atoms for cold atom experiments has increased in part due to their complex structure. This gives rise to a plethora of optical wavelengths to choose from, allowing for high flexibility. We have recently demonstrated trapping and imaging of single dysprosium atoms in optical tweezers, making use of dysprosium’s complex structure to find a magic trapping condition at 532nm.
Date: Fri, 19.01.2024
Time: 14:15
Duration: 45 min
Location:library TU Atominstitut
Contact:Marvin Holten