Publications (69)
Analytical results for non-linear Compton scattering in short intense laser pulses
Daniel Seipt, Vasily Kharin, Sergey Rykovanov +2
We study in detail the strong-field QED process of non-linear Compton scattering in short intense plane wave laser pulses of circular polarization. Our main focus is placed on how…
Electron angular distributions in the two--photon ionization of hydrogen--like ions: relativistic description
Peter Koval, Stephan Fritzsche, Andrey Surzhykov
The angular distribution of the emitted electrons, following the two--photon ionization of the hydrogen--like ions, is studied within the framework of second order perturbation the…
Atomic ionization by twisted photons: Angular distribution of emitted electrons
Oliver Matula, Armen G Hayrapetyan, Valeriy G Serbo +2
We investigate the angular distribution of electrons that are emitted in the ionization of hydrogen-like ions by twisted photons. Analysis is performed based on the first-order per…
Twisting harmonics: Transfer of orbital angular momentum in solid-state high-harmonic generation
Debobrata Rajak, Bikash Kumar Das, Rajaram Shrestha +7
Although solid-state platforms underpin modern electronics, little is known about how intense ultrashort light pulses carrying orbital angular momentum (OAM) interact with solids.…
Mass- and field-shift isotope parameters for the resonance doublet of lithium-like ions
Jiguang Li, Cédric Nazé, Michel Godefroid +4
It was recently shown that dielectronic recombination measurements can be used for accurately inferring changes in the nuclear mean-square charge radii of highly-charged lithium-li…
Large differential attosecond delays in solid state photoemission
Andreas Gebauer, Walter Enns, Sergej Neb +11
Time-resolved photoelectron spectroscopy provides access to the electronic structure and non-equilibrium electron dynamics in matter. At solid surfaces photoemission dynamics can b…
Maximizing the Validity of the Gaussian Approximation for the biphoton State from Parametric Downconversion
Baghdasar Baghdasaryan, Fabian Steinlechner, Stephan Fritzsche
Spontaneous parametric down-conversion (SPDC) is widely used in quantum applications based on photonic entanglement. The efficiency of photon pair generation is often characterized…
Electromagnetic wave propagation in spatially homogeneous yet smoothly time-varying dielectric media
Armen G. Hayrapetyan, Jörg B. Götte, Karen K. Grigoryan +2
We explore the propagation and transformation of electromagnetic waves through spatially homogeneous yet smoothly time-dependent media within the framework of classical electrodyna…
High-dimensional maximally entangled photon pairs in parametric down-conversion
Richard Bernecker, Baghdasar Baghdasaryan, Stephan Fritzsche
Photon pairs generated from spontaneous parametric down-conversion are a well-established method to realize entangled bipartite photonic systems. Laguerre-Gaussian modes, which car…
Radiative Capture of Twisted Electrons by Bare Ions
Oliver Matula, Armen G. Hayrapetyan, Valeriy G. Serbo +2
Recent advances in the production of twisted electron beams with a subnanometer spot size offer unique opportunities to explore the role of orbital angular momentum (OAM) in basic…
Discrete Cavity Dynamics in Free-Space Brillouin Laser
Jiabao Peng, Longjie Zhang, Zhenxu Bai +2
Highly coherent lasers are central to modern photonics. To date, high-coherence operation has been achieved predominantly in microcavity and fiber-based platforms. More recently, f…
Hyperfine-induced effects on the linear polarization of the K emission from helium-like ions
Andrey Surzhykov, Yuri A. Litvinov, Thomas Stöhlker +1
The linear polarization of the characteristic photon emission from few-electron ions is studied for its sensitivity with regard to the nuclear spin and magnetic moment of the ions.…
Laser Resonance Chromatography of Th in He: an ab initio investigation
Giorgio Visentin, Anastasia Borschevsky, Larry A. Viehland +2
We propose a laser resonance chromatography (LRC) experiment on Th, with the goal of detecting the ion's electronic ground F state and metastable $7…
Torus Knot Angular Momentum in Twisted Attosecond Pulses from High Harmonic Generation
Björn Minneker, Birger Böning, Anne Weber +1
Bicircular twisted Laguerre-Gaussian beams possess a definite torus knot angular momentum (TKAM) as a new form of angular momentum. TKAM is conserved in nonlinear atomic processes…
Delocalization of quantum information in long-range interacting systems
Darvin Wanisch, Stephan Fritzsche
We investigate the delocalization of quantum information in the nonequilibrium dynamics of the spin chain with asymptotically decaying interactions . As a figure…
High-precision calculations of the spin-allowed transition in C {\small III}
Moazzam Bilal, Andrey V Volotka, Randolf Beerwerth +3
Large-scale relativistic calculations are performed for the transition energy and line strength of the transition in Be-like…
Chemical Evolution of R-process Elements in Stars (CERES): IV. An observational run-up of the third r-process peak with Hf, Os, Ir, and Pt
Arthur Alencastro Puls, Jan Kuske, Camilla Juul Hansen +8
The third r-process peak (Os, Ir, Pt) is poorly understood due to observational challenges, with spectral lines located in the blue or near-ultraviolet region of stellar spectra. T…
Enhancing narrowband high order harmonic generation by Fano resonances
Jan Rothhardt, Steffen Hädrich, Stefan Demmler +4
Resonances in the photo-absorption spectrum of the generating medium can modify the spectrum of high order harmonics. In particular, window-type Fano resonances can reduce photo-ab…
Line strengths of QED-sensitive forbidden transitions in B-, Al-, F- and Cl-like ions
Moazzam Bilal, Andrey V Volotka, Randolf Beerwerth +1
The magnetic dipole (M1) line strength between the fine-structure levels of the ground configurations in B-, F-, Al- and Cl-like ions are calculated for the four elements argon, ir…
Spectral Properties of Transverse Laguerre-Gauss Modes in Parametric Down-Conversion
Carlos Sevilla-Gutiérrez, Varun Raj Kaipalath, Baghdasar Baghdasaryan +3
The first color photos of the parametric down-conversion (PDC) emission cone illustrate the correlation of longitudinal- and transverse momentum in the process, i.e., wavelength-de…
Interaction of vector light beams with atoms exposed to a time-dependent magnetic field
Shreyas Ramakrishna, Riaan P. Schmidt, Anton A. Peshkov +3
During recent years interest has been rising for applications of vector light beams towards magnetic field sensing. In particular, a series of experiments were performed to extract…
Transport property predictions for laser resonance chromatography on Rf (Z = 104)
Giorgio Visentin, Harry Ramanantoanina, Anastasia Borschevsky +5
We propose a theoretically designed laser resonance chromatography (LRC) experiment on Rf (Z = 104) drifting in He buffer gas. To this end, we first developed a four-level rate…
Coincidence measurement of two-photon double ionization of argon through an autoionizing resonance
Sebastian Hell, Julian Späthe, Morten Førre +8
We present coincidence measurements of two-photon double-ionization (TPDI) of argon driven by femtosecond pulses tunable around 26.5 eV photon energy, which are obtained from a hig…
Exploring Valence Electron Dynamics of Xenon through Laser-Induced Electron Diffraction
Fang Liu, Slawomir Skruszewicz, Julian Späthe +11
Strong-field ionization can induce electron motion in both the continuum and the valence shell of the parent ion. Here, we explore their interplay by studying laser-induced electro…
Relativistic polarization analysis of Rayleigh scattering by atomic hydrogen
Laleh Safari, Pedro Amaro, Stephan Fritzsche +3
A relativistic analysis of the polarization properties of light elastically scattered by atomic hydrogen is performed, based on the Dirac equation and second order perturbation the…
Angular distribution studies on the two-photon ionization of hydrogen-like ions: Relativistic description
Peter Koval, Stephan Fritzsche, Andrey Surzhykov
The angular distribution of the emitted electrons, following the two-photon ionization of the hydrogen-like ions, is studied within the framework of second order perturbation theor…
Collinear laser spectroscopy of atomic cadmium
Nadja Frömmgen, Dimiter L. Balabanski, Mark L. Bissell +16
Hyperfine structure and factors of the atomic transition are determined from collinear laser spectroscopy data of…
Nondipole strong-field approximation for above threshold ionization in few-cycle pulse
Danish Furekh Dar, Björn Minneker, Stephan Fritzsche
The ionization of atoms and molecules by strong laser fields has been studied extensively, both theoretically and experimentally. The strong-field approximation (SFA) allows for th…
Near L-Edge Single and Multiple Photoionization of Doubly Charged Iron Ions
Stefan Schippers, Randolf Beerwerth, Sadia Bari +11
Using the photon-ion merged-beams technique at a synchrotron light source, we have measured relative cross sections for single and up to five-fold photoionization of Fe ions…
Proton-neutron pairing correlations in the self-conjugate nucleus Sc
Agota Koszorus, Liam Vormawah, Randolf Beerwerth +16
Collinear laser spectroscopy of the self-conjugate nucleus Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-squ…
Enhancing the purity of single photons in parametric down-conversion through simultaneous pump-beam and crystal-domain engineering
Baghdasar Baghdasaryan, Fabian Steinlechner, Stephan Fritzsche
Spontaneous parametric down-conversion (SPDC) has shown great promise in the generation of pure and indistinguishable single photons. Photon pairs produced in bulk crystals are hig…
Spatial and temporal characteristics of spontaneous parametric down-conversion with varying focal planes of interacting beams
Richard Bernecker, Baghdasar Baghdasaryan, Stephan Fritzsche
Spontaneous parametric down-conversion (SPDC) is a widely used process to prepare entangled photon pairs. In SPDC, a second-order nonlinear crystal is pumped by a coherent laser be…
MCDHF calculations of the electric dipole moment of radium induced by the nuclear Schiff moment
Jacek Bieron, Gediminas Gaigalas, Erikas Gaidamauskas +3
The multiconfiguration Dirac-Hartree-Fock theory (MCDHF) has been employed to calculate the electric dipole moment of the 7s6d 3D2 state of radium induced by the nuclear Schiff mom…
Modification of multipole transitions by twisted light
Sabrina. A. -L. Schulz, Stephan Fritzsche, Robert A. Müller +1
A theoretical analysis is presented for the excitation of single many-electron atoms and ions by twisted (or vortex) light. Special emphasis is put on excitations that can proceed…
Hanle effect for lifetime determinations in the soft X-ray regime
Moto Togawa, Jan Richter, Chintan Shah +16
By exciting a series of transitions in helium-like nitrogen ions with linearly polarized mono…
Strong higher-order resonant contributions to x-ray line polarization in hot plasmas
Chintan Shah, Pedro Amaro, Rene Steinbrügge +6
We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic ch…
Relativistic central--field Green's functions for the RATIP package
Peter Koval, Stephan Fritzsche
From perturbation theory, Green's functions are known for providing a simple and convenient access to the (complete) spectrum of atoms and ions. Having these functions available, t…
Universal quantum Controlled-NOT gate
Michael Siomau, Stephan Fritzsche
An investigation of an optimal universal unitary Controlled-NOT gate that performs a specific operation on two unknown states of qubits taken from a great circle of the Bloch spher…
multiconfigurational calculations of experimentally significant energy levels and transition rates in Lr I
Joseph S. Andrews, Andrey I. Bondarev, Per Jönsson +4
Large-scale multiconfigurational calculations are conducted on experimentally significant transitions in Lr I and its lanthanide homologue Lu I, exhibiting good agreement with rece…
Comparison between Jacobi-Anger and saddle point methods to treat Above-threshold ionization
Danish Furekh Dar, Stephan Fritzsche
We present a detailed comparison of theoretical approaches for modeling strong-field ionization by few-cycle laser pulses. The dipole approximation is shown to accurately capture i…
Near L-edge photoionization of triply charged iron ions
Randolf Beerwerth, Ticia Buhr, Alexander Perry-SaÃmannshausen +12
Relative cross sections for -fold photoionization () of Fe by single photon absorption were measured employing the photon-ion merged-beams setup PIPE at the…
Polarization measurement of dielectronic recombination transitions in highly charged krypton ions
Chintan Shah, Holger Jörg, Sven Bernitt +10
We report linear polarization measurements of x rays emitted due to dielectronic recombination into highly charged krypton ions. The ions in the He-like through O-like charge state…
Transport of intense ion beams in plasmas: collimation and energy-loss reduction
Yongtao Zhao, Benzheng Chen, Dong Wu +15
We compare the transport properties of a well-characterized hydrogen plasma for low and high current ion beams. The energy-loss of low current beams can be well understood, within…
Relativistic calculations of the non-resonant two-photon ionization of neutral atoms
Jiri Hofbrucker, Andrey V. Volotka, Stephan Fritzsche
The non-resonant two-photon one-electron ionization of neutral atoms is studied theoretically in the framework of relativistic second-order perturbation theory and independent part…
Evolution equation of entanglement for multi-qubit systems
Michael Siomau, Stephan Fritzsche
We discuss entanglement evolution of a multi-qubit system when one of its qubits is subjected to a general noisy channel. For such a system, an evolution equation of entanglement f…
Entanglement dynamics of three-qubit states in noisy channels
Michael Siomau, Stephan Fritzsche
We study entanglement dynamics of the three-qubit system which is initially prepared in pure Greenberger-Horne- Zeilinger (GHZ) or W state and transmitted through one of the Pauli…
High-fidelity copies from a symmetric 1 to 2 quantum cloning machine
Michael Siomau, Stephan Fritzsche
A symmetric 1 to 2 quantum cloning machine (QCM) is presented that provides high-fidelity copies with for all pure (single-qubit) input states from a given me…
Relativistic and retardation effects in the two--photon ionization of hydrogen--like ions
Peter Koval, Stephan Fritzsche, Andrey Surzhykov
The non-resonant two-photon ionization of hydrogen-like ions is studied in second-order perturbation theory, based on the Dirac equation. To carry out the summation over the comple…
LCLS in - photon out: fluorescence measurement of neon using soft x-rays
Razib Obaid, Christian Buth, Georgi L. Dakovski +10
We measured the fluorescence photon yield of neon upon soft x-ray ionization (~1200 eV) from the x-ray free electron laser at Linac Coherent Light Source, and demonstrated the usag…
Hyperfine interaction with the Th nucleus and its low lying isomeric state
Robert A. Müller, Anna V. Maiorova, Stephan Fritzsche +8
The thorium nucleus with mass number has attracted much interest because its extremely low lying first excited isomeric state at about eV opens the possibility for the d…
Surprising charge-radius kink in the Sc isotopes at N=20
Kristian König, Stephan Fritzsche, Gaute Hagen +11
Charge radii of neutron deficient 40Sc and 41Sc nuclei were determined using collinear laser spectroscopy. With the new data, the chain of Sc charge radii extends below the neutron…
Quadratic Zeeman and Electric Quadrupole Shifts in Highly Charged Ions
Jan Gilles, Stephan Fritzsche, Lukas J. Spieà +2
Recent advances in high-precision spectroscopy of highly charged ions necessitate an understanding of energy shifts of ionic levels caused by external electric and magnetic fields.…
Algebraic tools for dealing with the atomic shell model. I. Wavefunctions and integrals for hydrogen--like ions
Andrey Surzhykov, Peter Koval, Stephan Fritzsche
Today, the 'hydrogen atom model' is known to play its role not only in teaching the basic elements of quantum mechanics but also for building up effective theories in atomic and mo…
Engineering of maximally entangled orbital angular momentum states via path identity
Richard Bernecker, Baghdasar Baghdasaryan, Stephan Fritzsche
Cutting-edge quantum technologies lean on sources of high-dimensional entangled states (HDES) that reliably prepare high-fidelity target states. The idea to overlap photon paths fr…
Coulomb excitation of hydrogen atoms by vortex ion beams
Anna V. Maiorova, Dmitry Karlovets, Stephan Fritzsche +2
Coulomb excitation of hydrogen atoms by vortex protons is theoretically investigated within the framework of the non--relativistic first--Born approximation and the density matrix…
The effect of bound state dressing in laser assisted radiative recombination
Robert Alexander Müller, Daniel Seipt, Stephan Fritzsche +1
We present a theoretical study on the recombination of a free electron into the ground state of a hydrogen-like ion in the presence of an external laser field. Emphasis is placed o…
Comparison of theory and experiment for radiative characteristics in neutral thulium
Andrey I. Bondarev, Maris Tamanis, Ruvin Ferber +4
Intensities in Tm I emission series originating from a common upper level are measured using a Fourier transform spectrometer. The derived relative transition probabilities within…
Quantum correlations in the two-photon decay of few-electron ions
Filippo Fratini, Malte Christopher Tichy, Thorsten Jahrsetz +3
A theoretical study of the polarization entanglement of two photons emitted in the decay of metastable ionic states is performed within the framework of density matrix theory and s…
Information Scrambling and the Correspondence of Entanglement- and Operator Dynamics in Systems with Nonlocal Interactions
Darvin Wanisch, Juan Diego Arias Espinoza, Stephan Fritzsche
How fast quantum information scrambles such that it becomes inaccessible by local probes turns out to be central to various fields. Motivated by recent works on spin systems with n…
Generalized description of the spatio-temporal biphoton State in spontaneous parametric down-conversion
Baghdasar Baghdasaryan, Carlos Sevilla-Gutiérrez, Fabian Steinlechner +1
Spontaneous parametric down-conversion (SPDC) is a widely used source for photonic entanglement. Years of focused research have led to a solid understanding of the process, but a c…
Relativistic wave and Green's functions for hydrogen--like ions
Peter Koval, Stephan Fritzsche
The \textsc{Greens} library is presented which provides a set of C++ procedures for the computation of the (radial) Coulomb wave and Green's functions. Both, the nonrelativistic as…
Asynchronous Multi-photon Interference for Quantum Networks
Baghdasar Baghdasaryan, Karen Lozano-Méndez, Markus Leipe +11
Advanced quantum communication protocols require high-visibility quantum interference between photons generated at distant nodes, which places stringent demands on optical synchron…
Neon in ultrashort and intense x rays from free electron lasers
Christian Buth, Randolf Beerwerth, Razib Obaid +3
We theoretically examine neon atoms in ultrashort and intense x rays from free electron lasers and compare our results with data from experiments conducted at the Linac Coherent Li…
Near L-Edge Single and Multiple Photoionization of Singly Charged Iron Ions
Stefan Schippers, Michael Martins, Randolf Beerwerth +7
Absolute cross sections for m-fold photoionization (m=1,...,6) of Fe+ by a single photon were measured employing the photon-ion merged-beams setup PIPE at the PETRA III synchrotron…
Bessel beams of two-level atoms driven by a linearly polarized laser field
Armen G. Hayrapetyan, Oliver Matula, Andrey Surzhykov +1
We study Bessel beams of two-level atoms that are driven by a linearly polarized laser field. Starting from the Schroedinger equation, we determine the states of two-level atoms in…
Quantum computing with mixed states
Michael Siomau, Stephan Fritzsche
We discuss a model for quantum computing with initially mixed states. Although such a computer is known to be less powerful than a quantum computer operating with pure (entangled)…
Multiconfiguration calculations of electronic isotope shift factors in Al I
Livio Filippin, Randolf Beerwerth, Jörgen Ekman +3
The present work reports results from systematic multiconfiguration Dirac-Hartree-Fock calculations of electronic isotope shift factors for a set of transitions between low-lying s…
Bound-state Compton scattering of linearly polarized photons
Jonas Sommerfeldt, Nick M. Mayer, Anna Maiorova +4
We present a theoretical study of Compton scattering of X- and -rays by a -shell electron. Special attention is paid to the double-differential cross section and polarizatio…
Relativistic effects in the non-resonant two-photon K-shell ionization of neutral atoms
Jiri Hofbrucker, Andrey V. Volotka, Stephan Fritzsche
Relativistic effects in the non-resonant two-photon K-shell ionization of neutral atoms are studied theoretically within the framework of second-order perturbation theory. The non-…