Achievements of DK ALM PhD student researchers
Besides publications in scientific journals and research results, prizes were won and some papers were selected for front pages.
DK ALM scientific outreach project
Front Page Covers
Nina K. Bersenkowitsch, Sarah J. Madlener, Jakob Heller
Nina K. Bersenkowitsch, Sarah J. Madlener, Jakob Heller, Christian van der Linde, Milan Ončák, and Martin K. Beyer
Environ. Sci.: Atmos., 2023, 3, 10, 1396-1406
https://doi.org/10.1039/D3EA00039G
Spectroscopy of cluster aerosol models: IR and UV spectra of hydrated glyoxylate with and without sea salt
Abstract:
Glyoxylic acid is formed in the troposphere by oxidation of organic molecules. In sea salt aerosols, it is expected to be present as glyoxylate, integrated into the salt environment and strongly interacting with water molecules. In water, glyoxylate is in equilibrium with its gem-diol form. To understand the influence of water and salt on the photophysics and photochemistry of glyoxylate, we generate small model clusters containing glyoxylate by electrospray ionization and study them by Fourier-Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry. We used infrared multiple photon dissociation spectroscopy and UV/vis photodissociation spectroscopy for structural characterization as well as quantum chemical calculations to model the spectra and dissociation patterns. Resonant absorption of infrared radiation leads to water evaporation, which indicates that water and glyoxylate are separate molecular entities in a significant fraction of the clusters, in line with the observed absorption of UV light in the actinic region. Hydration of glyoxylate leads to a change of the dihedral angle in the CHOCOO−.H2O complex, causing a slight redshift of the S1 ← S0 transition. However, the barriers for internal rotation are below 5 kJ mol−1, which explains the broad S1 ← S0 absorption extending from about 320 to 380 nm. Most importantly, hydration hinders dissociation in the S1 state, thus enhancing the quantum yield of fluorescence combined with water evaporation. No C–C bond photolysis is observed, but due to the limited signal-to-noise ratio, it cannot be ruled out. The quantum yield, however, will be relatively low. Fluorescence dominates the photophysics of glyoxylate embedded in the dry salt cluster, but the quantum yield shifts towards internal conversion upon addition of one or two water molecules.
Yusuf Karli
Yusuf Karli, Florian Kappe, Vikas Remesh, Thomas K. Bracht, Julian Münzberg, Saimon Covre da Silva, Tim Seidelmann, Vollrath Martin Axt, Armando Rastelli, Doris E. Reiter, and Gregor Weihs
SUPER Scheme in Action: Experimental Demonstration of Red-Detuned Excitation of a Quantum Emitter
Abstract: The quest for the perfect single-photon source includes finding the optimal protocol for exciting the quantum emitter. Coherent optical excitation was, up until now, achieved by tuning the laser pulses to the transition frequency of the emitter, either directly or in average. Recently, it was theoretically discovered that an excitation with two red-detuned pulses is also possible where neither of which would yield a significant upper-level population individually. We show that the so-called swing-up of quantum emitter population (SUPER) scheme can be implemented experimentally with similar properties to existing schemes by precise amplitude shaping of a broadband pulse. Because of its truly off-resonant nature, this scheme has the prospect of powering high-purity photon sources with superior photon count rate.
Maximilian Zanner
Maximilian Zanner, Tuure Orell, Christian M.F. Schneider, Romain Albert, Stefan Oleschko, Mathieu L. Juan, Matti Silveri and Gerhard Kirchmair
Nature Physics, 2022, volume 18, pages 538–543
https://www.nature.com/articles/s41567-022-01527-w
Coherent control of a multi-qubit dark state in waveguide quantum electrodynamics
Abstract: Superconducting qubits in a waveguide have long-range interactions mediated by photons that cause the emergence of collective states. Destructive interference between the qubits decouples the collective dark states from the waveguide environment. Their inability to emit photons into the waveguide render dark states a valuable resource for preparing long-lived quantum many-body states and realizing quantum information protocols in open quantum systems. However, they also decouple from fields that drive the waveguide, making manipulation a challenge. Here we show the coherent control of a collective dark state that is realized by controlling the interactions between four superconducting transmon qubits and local drives. The dark state’s protection against decoherence results in decay times that exceed those of the waveguide-limited single qubits by more than two orders of magnitude. Moreover, we perform a phase-sensitive spectroscopy of the two-excitation manifold and reveal bosonic many-body statistics in the transmon array. Our dark-state qubit provides a starting point for implementing quantum information protocols with collective states.
Jakob Heller
Jakob Heller, Ethan M. Cunningha, Jessica C. Hartmann, Christian van der Linde, Milan Ončák, and Martin K. Beyer
Phys. Chem. Chem. Phys., 2022, 24, 14699-14708
https://doi.org/10.1039/D2CP00833E
Size-dependent H and H2 formation by infrared multiple photon dissociation spectroscopy of hydrated vanadium cations, V+(H2O)n, n = 3–51
Abstract: Infrared spectra of the hydrated vanadium cation (V+(H2O)n; n = 3–51) were measured in the O–H stretching region employing infrared multiple photon dissociation (IRMPD) spectroscopy. Spectral fingerprints, along with size-dependent fragmentation channels, were observed and rationalized by comparing to spectra simulated using density functional theory. Photodissociation leading to water loss was found for cluster sizes n = 3–7, consistent with isomers featuring intact water ligands. Loss of molecular hydrogen was observed as a weak channel starting at n = 8, indicating the advent of inserted isomers, HVOH+(H2O)n−1. The majority of ions for n = 8, however, are composed of two-dimensional intact isomers, concordant with previous infrared studies on hydrated vanadium. A third channel, loss of atomic hydrogen, is observed weakly for n = 9–11, coinciding with the point at which the H and H2O calculated binding energies become energetically competitive for intact isomers. A clear and sudden spectral pattern and fragmentation channel intensity at n = 12 suggest a structural change to inserted isomers. The H2 channel intensity decreases sharply and is not observed for n = 20 and 25–51. IRMPD spectra for clusters sizes n = 15–51 are qualitatively similar indicating no significant structural changes, and are thought to be composed of inserted isomers, consistent with recent electronic spectroscopy experiments.
Jakob Heller
Jakob Heller, Tobias F. Pascher, Dominik Muß, Christian van der Linde, Martin K. Beyer, and Milan Ončák
Abstract: Photochemical hydrogen evolution provides fascinating perspectives for light harvesting. Hydrated metal ions in the gas phase are ideal model systems to study elementary steps of this reaction on a molecular level. Here we investigate mass-selected hydrated monovalent vanadium ions, with a hydration shell ranging from 1 to 41 water molecules, by photodissociation spectroscopy. The most intense absorption bands correspond to 3d–4p transitions, which shift to the red from n = 1 to n = 4, corresponding to the evolution of a square-planar complex. Additional water molecules no longer interact directly with the metal center, and no strong systematic shift is observed in larger clusters. Evolution of atomic and molecular hydrogen competes with loss of water molecules for all V+(H2O)n, n ≤ 12. For n ≥ 15, no absorptions are observed, which indicates that the cluster ensemble is fully converted to HVOH+(H2O)n−1. For the smallest clusters, the electronic transitions are modeled using multireference methods with spin–orbit coupling. A large number of quintet and triplet states is accessible, which explains the broad features observed in the experiment. Water loss most likely occurs after a series of intersystem crossings and internal conversions to the electronic ground state or a low-lying quintet state, while hydrogen evolution is favored in low lying triplet states.
Franziska Dahlmann
Franziska Dahlmann, Christine Lochmann, Aravingh N. Marimuthu, Miguel Lara-Moreno, Thierry Stoecklin, Philippe Halvick, Maurice Raoult, Olivier Dulieu, Robert Wild, Stephan Schlemmer, Sandra Brünken, and Roland Wester
J. Chem. Phys., 2021, 155, 241101
https://doi.org/10.1063/5.0073749
Strong ortho/para effects in the vibrational spectrum of Cl−(H2)
Abstract: The predissociation spectrum of the 35Cl-(H2) complex is measured between 450 and 800 cm−1 in a multipole radiofrequency ion trap at different temperatures using the FELIX infrared free electron laser. Above a certain temperature, the removal of the Cl−(p-H2) para nuclear spin isomer by ligand exchange to the Cl−(o-H2) ortho isomer is suppressed effectively, thereby making it possible to detect the spectrum of this more weakly bound complex. At trap temperatures of 30.5 and 41.5 K, we detect two vibrational bands of Cl−(p-H2) at 510(1) and 606(1) cm−1. Using accurate quantum calculations, these bands are assigned to transitions to the inter-monomer vibrational modes (v1, v2l2) = (0, 20) and (1, 20), respectively.
Govind Unnikrishnan
Phys. Rev. Lett., 2021, 125, 133001
https://doi.org/10.1063/5.0049320
Interaction-Enhanced Group Velocity of Bosons in the Flat Band of an Optical Kagome Lattice
Abstract: Geometric frustration of particle motion in a kagome lattice causes the single-particle band structure to have a flat s-orbital band. We probe this band structure by placing a Bose-Einstein condensate into excited Bloch states of an optical kagome lattice, and then measuring the group velocity through the atomic momentum distribution. We find that interactions renormalize the band structure, greatly increasing the dispersion of the third band, which is nearly non-dispersing the single-particle treatment. Calculations based on the lattice Gross-Pitaevskii equation indicate that band structure renormalization is caused by the distortion of the overall lattice potential away from the kagome geometry by interactions.
Jakob Heller
Jakob Heller, Tobias F. Pascher, Christian van der Linde, Milan Ončák, and Martin K. Beyer
Chem. Eur. J., 2021, 66
Abstract: More complex than expected: Photochemical hydrogen evolution in Al+(H2O)n involves conical intersections, multiple intersystem crossings between singlet and triplet surfaces, and electron transfer. Three neutral photoproducts are observed—hydrogen atoms, hydrogen molecules, and water. For the Al+(H2O)2 cluster, we show how a hydrogen radical is ejected and dictates reactivity. Our results underline the multitude of pathways in photochemistry of these seemingly simple ions.
Poster Prizes
David Weßmayer / David Wessmayer
David Wessmayer, Norbert Przybilla, Keith Butler
Contribution submission to the conference SMuK 2023
Quantitative spectroscopy of B-type supergiants
Abstract: B-type supergiants are a resourceful tool in adressing various astrophysical questions concerning stellar atmospheres, stellar and galactic evolution and the cosmic distance scale. To facilitate a comprehensive analysis of these objects we assess the applicability of a hybrid non-LTE approach, in which line-blanketed model atmospheres computed under the assumptions of local thermodynamic equilibrium (LTE) are combined with non-LTE line-formation calculations. High-resolution Echelle spectra – constituting an observational sample of 14 Galactic B-type supergiants with masses below about 30 𝑀⊙ – serve as the basis of this investigation. The results of the analysis, including atmospheric and fundamental stellar parameters, multi-species abundances and derived spectroscopic distances, are probed via multiple checks of consistency. Finally, we also test the employed methodology for analyses of intermediate-resolution spectra of extragalactic B-type supergiants.
Dasarath Swaraj
Dasarth Swaraj, Jerin Judy, Tim Michaelsen, Fabio Zappa, Arnab Khan, Robert Wild and Roland Wester
799. WE-Heraeus-Seminar on Laboratory Astrophyiscs
September 2023, Heidelberg, DE
Simulated H3+ product ion distribution for assumed isotropic scattering and vibrational state population according to degeneracy
Abstract: Crossed-beam reactive scattering experiments offer a detailed understanding of the dynamics involved in elementary reactions occurring in the gas phase. By employing velocity map imaging (VMI), it is possible to acquire angle and energy differential cross-sections, as demonstrated in previous studies. In this study, we present a comprehensive design plan and relevant simulations for an experimental setup intended to investigate ion-molecule reactions with enhanced precision to achieve stateto-state resolution for ion-molecule reactions.
Initially, we are concentrating on the experimental studies on the ion-molecule reaction H2+ + H2 → H3+ + H. Additionally, Monte
Carlo simulations were conducted to determine the expected resolution of the product energy for the reaction. To generate H₂⁺
ions, we employ laser-induced ionization of H₂ using the 3rd or 4th harmonic of a pulsed Nd:YAG laser, ensuring that the ions
primarily occupy the vibrational ground state. The ion beam is then overlapped with a beam of neutral molecules, and the
resulting collision products are collected and analyzed using the VMI spectrometer. Furthermore, we plan to implement
coincidence detection to simultaneously observe both the ionic and neutral products subsequent to the reaction.
Franziska Dahlmann
Franziska Dahlmann, Christine Lochmann, Aravindh N. Marimuthu, Miguel Lara-Moreno, Thierry Stoecklin, Philippe Halvick, Maurice Raoult, Olivier Dulieu, Robert Wild, Stephan Schlemmer, Sandra Brünken and Roland Wester
739. WE-Heraeus-Seminar on Molecular Physics and Physical Chemistry with Advanced Photon Sources
January 2022, Bad Honnef, DE
Strong ortho/para effects in the vibrational spectrum of Cl-(H2)
Abstract: The predissociation spectrum of the 35Cl-(H2) complex is measured between 450 and 800 cm-1 in a multipole radiofrequency ion trap at different temperatures using the FELIX infrared free electron laser. Above a certain temperature, the removal of the Cl-(para-H2) para nuclear spin isomer by ligand exchange to the Cl-(ortho-H2) ortho isomer is suppressed effectively, thereby making it possible to detect the spectrum of this more weakly bound complex. At trap temperatures of 30.5 and 41.5 K, we detect two vibrational bands of Cl-(para-H2) at 510(1) and 606(1) cm-1. Using accurate quantum calculations, these bands are assigned to transitions to the inter-monomer vibrational modes (ν1, ν2, l2) = (0, 2, 0 ) and (1, 2, 0), respectively.
Verena Scheil
Verena Scheil, Raphael Holzinger, Maria Moreno-Cardoner, and Helmut Ritsch
71th annual meeting of the ÖPG
Optical Properties of Nanoscopic Double-Rings of Quantum Emitters
Abstract: A single ring of sub-wavelength spaced dipole-coupled quantum emitters can exhibit very special optical features, in contrast to a one-dimensional chain of emitters. This includes the emergence of extremely subradiant collective eigenmodes whose lifetime increases exponentially with the atom number, and the existence of optical modes acting as those of an optical resonator.
Motivated by structures commonly appearing in natural light harvesting complexes we extend these studies to strongly coupled rings geometries. We find that a spin wave ansatz properly describes the radiation properties of double-ring structures, allowing us to study the rich behavior of superradiance and subradiance in these systems. We further proceed to analyze the collective eigenmodes of realistic light harvesting complexes in purple bacteria which share a similar coupled ring structure. These findings can be relevant in the context of excitation energy transport in both natural and artificial light harvesting complexes.
Matthias Englbrecht
Matthias Englbrecht, Tristan Kraft, and Barbara Kraus
Conference Entanglement in Action, Benasque Spain
Party-local Clifford transformations of stabilizer states
Abstract: Stabilizer states and graph states find application in quantum error correction, measurement-based quantum computation and various other concepts in quantum information theory. In this work, we study party-local Clifford (PLC) transformations among stabilizer states. These transformations arise as a physically motivated extension of local operations in quantum networks with access to bipartite entanglement between some of the nodes of the network. First, we show that PLC transformations among graph states are equivalent to a generalization of the well-known local complementation, which describes local Clifford transformations among graph states. Then, we introduce a new mathematical framework to study PLC equivalence of stabilizer states. This framework allows us to study decompositions of stabilizer states into tensor products of indecomposable ones, that is, decompositions into states from the entanglement generating set (EGS). While the EGS is finite up to 3 parties [Bravyi et al., J. Math. Phys. 47, 062106 (2006)], we show that for 4 and more parties it is an infinite set. Finally, we generalize the framework to qudit stabilizer states in prime dimensions not equal to 2, which allows us to show that qudit stabilizer states decompose uniquely into states from the EGS.
Yusuf Karli
Yusuf Karli, Florian Kappe, Vikas Remesh, Thomas K. Bracht, Julian Münzberg, Saimon Covre da Silva, Tim Seidelmann, Vollrath Martin Axt, Armando Rastelli, Doris E. Reiter, and Gregor Weihs
Photonic Quantum Technologies – A Revolution in Communication, Sensing, and Metrology
March 2022, Bad Honnef, DE
SUPER Scheme in Action: Experimental Demonstration of Red-detuned Excitation of a Quantum Dot
Abstract: The quest for the perfect single-photon source includes finding the optimal protocol for exciting the quantum emitter. Based on a recently proposed, so-called SUPER (swing-up of quantum emitter population) scheme, we demonstrate experimentally that two red-detuned laser pulses, neither of which could yield a significant upper-level population individually, lead to the coherent excitation of a semiconductor quantum dot. We characterize the emitted single photons and show that they have properties comparable to those achieved under resonant excitation schemes.
Magdalena Salzburger
Magdalena Salzburger, Milan Ončák, Christian van der Linde, and Martin K. Beyer
Unimolecular reaction Faraday Discussion
June 2022, Oxford, UK
A simplified multiple-well approach for the master equation modeling of blackbody infrared radiative dissociation (BIRD) of hydrated carbonate radical anions
Abstract: Molecular clusters CO3●‑(H2O)1,2 are found in the lower region of the ionosphere and in the troposphere. Investigation of their properties can be helpful to understand atmospheric chemistry. In this work, we analyze blackbody infrared radiative dissociation (BIRD) of singly and doubly hydrated carbonate radical anion clusters at different temperatures.
The molecular clusters are generated with a laser vaporisation source and guided to a Fourier Transformation Ion Cyclotron Resonance Mass Spectrometer (FT-ICR-MS). The temperature of the ICR-Cell can be regulated by a variable supply of liquid nitrogen or warm water.
We observe loss of water from CO3●‑(H2O)1,2 clusters. BIRD‑kinetics were measured for temperatures between 210 and 350 K. Dissociation kinetics are first order, and are fitted with a genetic algorithm to obtain unimolecular rate constants. The kinetics exhibit apparent Arrhenius behavior. Master equation modeling of the temperature dependent kinetics is performed, taking into account all low-lying isomers that are populated at the experimental temperatures. Densities of states calculated with the Beyer-Swinehart algorithm are compared with ab initio molecular dynamics simulations. Modeling yields binding energies, which are compared with quantum chemical calculations on the CCSD/aug-cc-pVDZ level of theory.
Anna Maria Reider
Anna Maria Reider, Felix Laimer, Fabio Zappa, Michael Gatchell, and Paul Scheier
14th International Conference on Quantum Fluid Clusters
April 2022, Erice, IT
Multiply Charged Superfluid Helium Droplets
Abstract: The poster presents our experimental approaches and the results that prove the existence of multiply charged anionic and cationic superfluid helium droplets. Anionic helium droplets carrying up to five charges and cations exceeding 50+ charge centres can be identified in the data and scaling laws for the distribution of the charge centres with the helium droplets are discussed.
Maximilian Sohmen
24th YAO conference
June 2018, Glasgow, UK
Versatile Experiment for ultracold Erbium, Dysprosium, and their Mixture
Awards & Prizes
Hendrik Poulsen-Nautrup
Alexey A. Melnikov, Hendrik Poulsen Nautrup, Mario Krenn, Vedran Dunjko, Markus Tiersch, Anton Zeilinger, and Hans J. Briegel
PNAS, 115 (6) 1221-1226
https://www.pnas.org/doi/10.1073/pnas.1714936115
Class I: Physical and Mathematical Sciences
The 2018 Cozzarelli Prize was awarded at the 156th Annual Meeting of the National Academy of Sciences in April 2019 in Washington, DC.
Abstract: Modern experiments in quantum physics have advanced researchers’ understanding of several fundamental concepts of quantum theory. However, further advances in quantum physics are likely to require complex experiments that are challenging to design and potentially counterintuitive. Melnikov, Poulsen Nautrup, et al. developed an artificial intelligence system capable of designing experiments for producing complex entangled photon states, which are difficult to realize experimentally. The system learned to design the desired experiments more efficiently than previous approaches, discovering nonstandard experimental techniques in the process. The work expands the possibilities for the role of machines in scientific research.
About Cozzarelli Prize: The Cozzarelli Prize is awarded annually to six research teams whose PNAS articles have made outstanding contributions to their field. Each team represents one of the six classes of the National Academy of Sciences (NAS): Physical and Mathematical Sciences; Biological Sciences; Engineering and Applied Sciences; Biomedical Sciences; Behavioral and Social Sciences; and Applied Biological, Agricultural, and Environmental Sciences.
David Sauerwein
David Sauerwein, Nolan R. Wallach, Gilad Gour, and Barbara Kraus
Phys. Rev. X 8, 031020
https://doi.org/10.1103/PhysRevX.8.031020
Transformations among Pure Multipartite Entangled States via Local Operations are Almost Never Possible
1st Prize for David Sauerwein - Thanksgiving 2018Zentrum für Kanadastudien an der Universität Innsbruck
Canadian Studies Centre - Centre d‘études canadiennes
Abstract: Local operations assisted by classical communication (LOCC) constitute the free operations in entanglement theory. Hence, the determination of LOCC transformations is crucial for the understanding of entanglement. We characterize here almost all LOCC transformations among pure multipartite multilevel states. Combined with the analogous results for qubit states shown by Gour et al. [J. Math. Phys. (N.Y.) 58, 092204 (2017)], this gives a characterization of almost all local transformations among multipartite pure states. We show that nontrivial LOCC transformations among generic, fully entangled, pure states are almost never possible. Thus, almost all multipartite states are isolated. They can neither be deterministically obtained from local-unitary-inequivalent (LU-inequivalent) states via local operations, nor can they be deterministically transformed to pure, fully entangled LU-inequivalent states. In order to derive this result, we prove a more general statement, namely, that, generically, a state possesses no nontrivial local symmetry. We discuss further consequences of this result for the characterization of optimal, probabilistic single-copy and probabilistic multicopy LOCC transformations and the characterization of LU-equivalence classes of multipartite pure states.
About Canada Award: Since the end of the 20th century the Canadian Studies Centre of the University of Innsbruck has been celebrating the "scientific harvest" of the current year with a special event in November, framed by music and lectures and recalling the North American "Thanksgiving" celebrations. This event is meant to present and honor promising young scholars of the University of Innsbruck who have dealt with Canadian Studies topics in their scientific work (thesis, article) or have collaborated with Canadian scholars.
DK ALM scientific outreach project
Hendrik Poulsen-Nautrup, Lea Trenkwalder
Fulvio Flamini, Hendrik Poulsen-Nautrup, Lea Trenkwalder (alphabethical order)
Seeker – A trading card game for outreach in science
Seeker has been sponsored by DK ALM trough the funding of the FWF, W1259-N27, and the Förderkreis 1669 at the University of Innsbruck. (https://www.uibk.ac.at/de/foerderkreis1669/)
Abstract: Science education has become progressively more central at a European level, as exemplified by the efforts put forth by the Horizon 2020 Work Programme. In this direction, the team aims to develop a trading card game – Seeker – which fully incarnates the attitudinal, cognitive and social objectives that are usually associated with outreach. Their ambitious project holds the potential to bring young generations closer to science.
As physicists, the team believes being scientists is both a privilege and a responsibility towards society. They believe that, while pursuing the truth according to the ethics standards, substantial effort should be devoted in shortening the distance from the general public. In the long term, this has concrete, practical consequences for science itself: raising science literacy increases the potential of the youngest generation, increases trust in scientists and enables a more efficient diffusion of results, among others. Hence, while their professional career is dedicated to advancing science, they are also driven by the wish to further enhance it, and, with it, to enhance society. Seeker allows them to make a step in this direction, by using a medium we are all familiar with: a trading card game and the power of internet.