Programm für das Wintersemester 2019/2020

Donnerstags, 14 Uhr c.t.

Ort: Institut für Physik, Lorentz-Raum (05-127), Staudingerweg 7

31.10.19Prof. Dr. Stephen D. Hogan, Department of Physics and Astronomy, University College London, UK
Rydberg states, the bound quantum states of an attractive 1/r potential, play a central role in many precision spectroscopic tests of fundamental physics with atoms and molecules, e.g., [1,2]. As perhaps the simplest Rydberg system, the positronium atom - composed of an electron bound to its antiparticle the positron, and therefore a purely leptonic system described almost entirely by bound state QED theory - offers unique opportunities for studies of this kind. However, because of its short ground-state annihilation lifetime (142 ns) many precision experiments with positronium must be performed with longer-lived excited states - Rydberg states. The efficient preparation of Rydberg states in positronium is now possible following developments in positron beam and trap technologies [3], and the motion of the atoms excited to these states can be controlled and manipulated using inhomogeneous electric fields through the methods of Rydberg-Stark deceleration [4]. In this talk I will describe new precision microwave spectroscopic measurements of the triplet n=2 fine structure in positronium that takes advantage of these developments. I will also present a new technique for performing matter-wave interferometry with atoms in Rydberg states that has been developed using helium atoms [5], but in the future could be exploited for accurate gravity measurements with Rydberg positronium. [1] A. Beyer, L. Maisenbacher, A. Matveev, R. Pohl, K. Khabarova, A. Grinin, T. Lamour, D. C. Yost, Th. W. Hänsch, N. Kolachevsky, and Th. Udem, The Rydberg constant and proton size from atomic hydrogen, Science 358, 79 (2017) [2] N. Hölsch, M. Beyer, E. J. Salumbides, K. S. E. Eikema, W. Ubachs, Ch. Jungen, and F. Merkt, Benchmarking Theory with an Improved Measurement of the Ionization and Dissociation Energies of H2, Phys. Rev. Lett. 122, 103002 (2019) [3] T. E. Wall, A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan, and D. B. Cassidy, Selective Production of Rydberg-Stark States of Positronium, Phys. Rev. Lett. 114, 173001 (2015) [4] S. D. Hogan, Rydberg-Stark deceleration of atoms and molecules, EPJ Techniques and Instrumentation 3, 1 (2016) [5] J. E. Palmer and S. D. Hogan, Electric Rydberg-atom interferometry, Phys. Rev. Lett. 122, 250404 (2019)
08.11.19Dr. Stephan Schlamminger, National Institute of Standards and Technology, Gaithersburg, USA
Up to May 20th this year, there was one mass on earth that we knew with absolute precision, i.e., zero uncertainty. This mass was the international prototype of the kilogram. Since May 20th, it is just another mass and thew mass unit is now defined via a fixed value of the Planck constant, h=6.62607015×〖10〗^(-34) "J s" with zero uncertainty. In this presentation, I will explain how the unit of mass can be realized at the kilogram scale via the Kibble balance and the X-ray crystal density method. In the present SI, it is, however, no longer necessary to realize the unit at the cardinal point of 1 kg, it can be realized at any scale. The talk will present some future possibilities of this scale invariant definition of the mass unit.

Sondertermin - Bitte um Beachtung!

14.11.19Dr. Johannes W. Deiglmayr, Felix-Bloch Institute, Universität Leipzig
Exciting an atom or molecule into a high-lying electronic state, a Rydberg state, changes its properties in a drastic, but very well-understood way. While the binding energy of the Rydberg electron decrease with the principal quantum number n as 1/n^2, the orbital radius and transition dipole moments increase as n^2. This results in the electric polarizability increasing as n^7. I will present recent experiments in which we have exploited these scaling laws and exaggerated properties to perform precision measurements of ionization energies with relative accuracies up to 10^11, to characterize precisely static and alternating electric fields, and to reduce the detrimental role of stray fields in applications of Rydberg atoms. In a second part, I’ll discuss our progress towards extracting accurate scattering phase shifts from the spectroscopy of hetero-nuclear long-range Rydberg molecules, which are bound by the interaction of the Rydberg electron with ground-state atoms within its orbit, and how we plan to exploit the exotic properties of long-range Rydberg molecules to create ultracold, strongly correlated plasmas.
zukünftige Termine
28.11.19Dr. Juan Manuel Cornejo-Garcia, Institut für Quantenoptik, Universität Hannover
Cosmological observations point to an apparent imbalance of matter and antimatter in our universe, which contrasts with the nearly perfect symmetry arising on the level of single particles. Tests for hypothetical limits to this symmetry rest on high precision comparisons of the fundamental properties of particles and antiparticles - for example, with measurements of the proton and antiproton g-factors in Penning traps. However, these measurements rely on cooling and detections schemes that are highly sensitive on the particle's motional energy [1,2]. In this talk, it will be shown an alternative experimental method which enables a speed up of the particles' preparation and a boost in readout fidelity in the respective experiments [3]. Our method allows for sympathetic cooling of a proton or antiproton to its quantum mechanical ground state and provides readout of their spin state, by means of coupling to a laser cooled 9Be+ ion co-trapped in a double well potential. In addition, an overview of the current experimental setup featuring a cryogenic Penning trap stack for first demonstrations of motional coupling between two 9Be+ ions will be presented. [1] C. Smorra et al., Nature 550, 371-374 (2017) [2] G. Schneider et al., Science 358, 1081-1084 (2017) [3] D. J. Wineland et al., J. Res. NIST 103, 259-328 (1998)
12.12.19Dr. Guillaume Salomon, Max-Planck-Institut für Quantenoptik, Garching
Developing new approaches to study quantum many-body systems is of fundamental importance in var­ious felds of physics ranging from high energy and condensed matter physics to quantum information and quantum computation. It also holds promise for a better understanding of materials, such as high-Tc superconductors, and fault-tolerant quantum computing which could strongly impact our modern soci­eties. Ultracold atoms have emerged as versatile and well controlled platforms to study fundamental problems in quantum many-body physics. In particular, spin-resolved quantum gas microscopy enables to probe strongly correlated fermions with a resolution down to the single particle and offers fascinating oppor­tunities for experiments. I will detail here this technique and discuss our recent experimental studies of the interplay between magnetism and doping in the Fermi-Hubbard model, a minimal model for high-Tc superconductivity.
19.12.19Prof. Dr. Sile Nic Chormaic, OIST Graduate University, Okinawa, Japan
Ultrathin optical fibres, with diameters on the order of the propagating light wavelength, have already proven their versatility across a variety of different areas, such as sensing, particle manipulation, cold atom physics, and as optical couplers. The intense evanescent field at the fibre waist is one of the main advantages offered by these systems as it allows us to achieve ultrahigh light intensities that may otherwise not be attainable in a standard laboratory. In this talk, I will present work conducted at OIST with particular focus on our work on optical nanofibre-mediated multiphoton processes for the generation of highly excited Rydberg atoms and for exploring some other effects, such as quadrupole transitions and stimulated emission from Rb atoms. Overall, the versatility of these fibres for many different experimental platforms particularly if one goes beyond the basic, single mode fibre design will be promoted.
16.01.20Dr. Tobias Jenke, Institut Laue Langevin, Grenoble, Frankreich
23.01.20Dr. Maria Chekhova, Institut für Optik, Information und Photonik, Universität Erlangen
30.01.20Prof. Dr. Philipp Haslinger, Atominstitut, TU Wien, Österreich
Koordinator und Kontakt:
Prof. Dr. Klaus Wendt
Institut fuer Physik, WA Quantum