@article{54865, author = {{Krenz, Marvin and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, number = {{7}}, publisher = {{American Physical Society (APS)}}, title = {{{Defect-Assisted Exciton Transfer across the Tetracene-Si(111):H Interface}}}, doi = {{10.1103/physrevlett.132.076201}}, volume = {{132}}, year = {{2024}}, } @article{62868, abstract = {{We theoretically investigate strategies for the deterministic creation of trains of time-bin entangled photons using an individual quantum emitter described by a Λ-type electronic system. We explicitly demonstrate the theoretical generation of linear cluster states with substantial numbers of entangled photonic qubits in full microscopic numerical simulations. The underlying scheme is based on the manipulation of ground state coherences through precise optical driving. One important finding is that the most easily accessible quality metrics, the achievable rotation fidelities, fall short in assessing the actual quantum correlations of the emitted photons in the face of losses. To address this, we explicitly calculate stabilizer generator expectation values as a superior gauge for the quantum properties of the generated many-photon state. With widespread applicability in other emitter and excitation–emission schemes also, our work lays the conceptual foundations for an in-depth practical analysis of time-bin entanglement based on full numerical simulations with predictive capabilities for realistic systems and setups, including losses and imperfections. The specific results shown in the present work illustrate that with controlled minimization of losses and realistic system parameters for quantum-dot type systems, useful linear cluster states of significant lengths can be generated in the calculations, discussing the possibility of scalability for quantum information processing endeavors.}}, author = {{Bauch, David and Köcher, Nikolas and Heinisch, Nils and Schumacher, Stefan}}, issn = {{2835-0103}}, journal = {{APL Quantum}}, number = {{3}}, publisher = {{AIP Publishing}}, title = {{{Time-bin entanglement in the deterministic generation of linear photonic cluster states}}}, doi = {{10.1063/5.0214197}}, volume = {{1}}, year = {{2024}}, } @article{62942, abstract = {{AbstractNanostructured bilayer thin films with superhydrophobic and superhydrophilic surfaces were prepared using Ti6Al4V alloy substrates which allowed for the comparative analysis of polyvinyl acetate (PVAc) particle adsorption as a function of the interface structure. The PVAc particles were obtained from emulsion polymerization of vinyl acetate. A superhydrophilic TiO2 nanofiber-based 3D network was created on the Ti6Al4V alloy substrate by application of a hydrothermal method. Subsequent UV-grafting of ultra-thin polydimethylsiloxane (PDMS) layers resulted in a superhydrophobic surface. The modification steps were followed via Diffuse Reflectance Infrared Fourier Transform Spectroscopy, X-ray Photoelectron Spectroscopy, Field Emission-Scanning Electron Microscopy, contact angle and Electrochemical Impedance Spectroscopy. A mechanism for the adsorption of PVAc at the two electrolyte/substrate interfaces could be revealed.}}, author = {{Neßlinger, Vanessa and Atlanov, Jan and Grundmeier, Guido}}, issn = {{3004-9261}}, journal = {{Discover Applied Sciences}}, number = {{6}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Interactions of polyvinyl acetate dispersions with nanostructured superhydrophilic and superhydrophobic Ti6Al4V alloy surfaces}}}, doi = {{10.1007/s42452-024-05916-z}}, volume = {{6}}, year = {{2024}}, } @article{53202, abstract = {{At large scales, quantum systems may become advantageous over their classical counterparts at performing certain tasks. Developing tools to analyze these systems at the relevant scales, in a manner consistent with quantum mechanics, is therefore critical to benchmarking performance and characterizing their operation. While classical computational approaches cannot perform like-for-like computations of quantum systems beyond a certain scale, classical high-performance computing (HPC) may nevertheless be useful for precisely these characterization and certification tasks. By developing open-source customized algorithms using high-performance computing, we perform quantum tomography on a megascale quantum photonic detector covering a Hilbert space of 106. This requires finding 108 elements of the matrix corresponding to the positive operator valued measure (POVM), the quantum description of the detector, and is achieved in minutes of computation time. Moreover, by exploiting the structure of the problem, we achieve highly efficient parallel scaling, paving the way for quantum objects up to a system size of 1012 elements to be reconstructed using this method. In general, this shows that a consistent quantum mechanical description of quantum phenomena is applicable at everyday scales. More concretely, this enables the reconstruction of large-scale quantum sources, processes and detectors used in computation and sampling tasks, which may be necessary to prove their nonclassical character or quantum computational advantage.}}, author = {{Schapeler, Timon and Schade, Robert and Lass, Michael and Plessl, Christian and Bartley, Tim}}, journal = {{Quantum Science and Technology}}, number = {{1}}, publisher = {{IOP Publishing}}, title = {{{Scalable quantum detector tomography by high-performance computing}}}, doi = {{10.1088/2058-9565/ad8511}}, volume = {{10}}, year = {{2024}}, } @inproceedings{53824, author = {{Koch, Kevin and Claes, Leander and Jurgelucks, Benjamin and Meihost, Lars and Henning, Bernd}}, booktitle = {{Fortschritte der Akustik - DAGA 2024}}, editor = {{Gesellschaft für Akustik e.V., Deutsche }}, pages = {{1113–1116}}, title = {{{Inverses Verfahren zur Identifikation piezoelektrischer Materialparameter unterstützt durch neuronale Netze}}}, year = {{2024}}, } @misc{55470, author = {{Koch, Kevin and Friesen, Olga and Claes, Leander}}, publisher = {{Zenodo}}, title = {{{Randomised material parameter impedance dataset of piezoelectric rings}}}, doi = {{10.5281/zenodo.13143680}}, year = {{2024}}, } @misc{53662, author = {{Koch, Kevin and Claes, Leander}}, publisher = {{zenodo}}, title = {{{Randomised material parameter piezoelectric impedance dataset with structured electrodes}}}, doi = {{10.5281/ZENODO.11064206}}, year = {{2024}}, } @misc{55416, author = {{Claes, Leander and Koch, Kevin and Friesen, Olga and Meihost, Lars}}, title = {{{Machine learning in inverse measurement problems: An application to piezoelectric material characterisation}}}, year = {{2024}}, } @article{54314, author = {{Koch, Kevin and Claes, Leander and Jurgelucks, Benjamin and Meihost, Lars}}, journal = {{tm - Technisches Messen}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{Neuronale Netze zur Startwertschätzung bei der Identifikation piezoelektrischer Materialparameter}}}, doi = {{10.1515/teme-2024-0099}}, year = {{2024}}, } @phdthesis{56654, abstract = {{Residual stresses in directly joined laminates made of steel and carbon fiber reinforced epoxy resin reduce the interface and bond strength and thus have to be taken into account for the strength analysis of structural components. For a holistic description of residual stresses, a thermo-chemo-mechanical constitutive model is introduced in the present work and presented for the multi-scale analysis of residual stress patterns. In this context, the analysis of representative unit cells with regular and stochastic distribution of fibers gives information about the associated deformation and stress fields. Dehomogenization at macroscopically highly stressed regions, characterized by local stress peaks, reveals the effect of gradient deformation in the microstructure. Another aspect of this work is the development of FFT-based Galerkin methods, which allows an evaluation of the effect of defect densities, heterogeneities and morphologies on the applicability of the incremental hole drilling method. It could be demonstrated that the incremental hole drilling method is particularly sensitive to defects running along the surface.}}, author = {{Tinkloh, Steffen Rainer}}, isbn = {{9783757887650}}, keywords = {{Hybride Werkstoffverbunde, Eigenspanungen, FFT-basierte Galerkin-Methode, Mikromechanik, Finite-Elemente-Methode}}, pages = {{168}}, publisher = {{BoD - Books on Demand}}, title = {{{Mikromechanische Analyse von Eigenspannungen in direktgefügten kohlenstofffaserverstärkten Kunststoff-Stahl-Schichtverbunden}}}, year = {{2024}}, } @inproceedings{56481, author = {{Berganski, Christoph and Jentzsch, Felix and Platzner, Marco and Kuhmichel, Max and Giefers, Heiner}}, location = {{Sydney}}, title = {{{FINN-T: Compiling Custom Dataflow Accelerators for Quantized Transformers}}}, year = {{2024}}, } @misc{54245, author = {{Henke, Luca-Sebastian}}, title = {{{Exploring Custom FPGA Accelerators for DNN-based RF Fingerprinting}}}, year = {{2024}}, } @article{21199, abstract = {{As in almost every other branch of science, the major advances in data science and machine learning have also resulted in significant improvements regarding the modeling and simulation of nonlinear dynamical systems. It is nowadays possible to make accurate medium to long-term predictions of highly complex systems such as the weather, the dynamics within a nuclear fusion reactor, of disease models or the stock market in a very efficient manner. In many cases, predictive methods are advertised to ultimately be useful for control, as the control of high-dimensional nonlinear systems is an engineering grand challenge with huge potential in areas such as clean and efficient energy production, or the development of advanced medical devices. However, the question of how to use a predictive model for control is often left unanswered due to the associated challenges, namely a significantly higher system complexity, the requirement of much larger data sets and an increased and often problem-specific modeling effort. To solve these issues, we present a universal framework (which we call QuaSiModO: Quantization-Simulation-Modeling-Optimization) to transform arbitrary predictive models into control systems and use them for feedback control. The advantages of our approach are a linear increase in data requirements with respect to the control dimension, performance guarantees that rely exclusively on the accuracy of the predictive model, and only little prior knowledge requirements in control theory to solve complex control problems. In particular the latter point is of key importance to enable a large number of researchers and practitioners to exploit the ever increasing capabilities of predictive models for control in a straight-forward and systematic fashion.}}, author = {{Peitz, Sebastian and Bieker, Katharina}}, journal = {{Automatica}}, publisher = {{Elsevier}}, title = {{{On the Universal Transformation of Data-Driven Models to Control Systems}}}, doi = {{10.1016/j.automatica.2022.110840}}, volume = {{149}}, year = {{2023}}, } @article{35602, abstract = {{Continuous Speech Separation (CSS) has been proposed to address speech overlaps during the analysis of realistic meeting-like conversations by eliminating any overlaps before further processing. CSS separates a recording of arbitrarily many speakers into a small number of overlap-free output channels, where each output channel may contain speech of multiple speakers. This is often done by applying a conventional separation model trained with Utterance-level Permutation Invariant Training (uPIT), which exclusively maps a speaker to an output channel, in sliding window approach called stitching. Recently, we introduced an alternative training scheme called Graph-PIT that teaches the separation network to directly produce output streams in the required format without stitching. It can handle an arbitrary number of speakers as long as never more of them overlap at the same time than the separator has output channels. In this contribution, we further investigate the Graph-PIT training scheme. We show in extended experiments that models trained with Graph-PIT also work in challenging reverberant conditions. Models trained in this way are able to perform segment-less CSS, i.e., without stitching, and achieve comparable and often better separation quality than the conventional CSS with uPIT and stitching. We simplify the training schedule for Graph-PIT with the recently proposed Source Aggregated Signal-to-Distortion Ratio (SA-SDR) loss. It eliminates unfavorable properties of the previously used A-SDR loss and thus enables training with Graph-PIT from scratch. Graph-PIT training relaxes the constraints w.r.t. the allowed numbers of speakers and speaking patterns which allows using a larger variety of training data. Furthermore, we introduce novel signal-level evaluation metrics for meeting scenarios, namely the source-aggregated scale- and convolution-invariant Signal-to-Distortion Ratio (SA-SI-SDR and SA-CI-SDR), which are generalizations of the commonly used SDR-based metrics for the CSS case.}}, author = {{von Neumann, Thilo and Kinoshita, Keisuke and Boeddeker, Christoph and Delcroix, Marc and Haeb-Umbach, Reinhold}}, issn = {{2329-9290}}, journal = {{IEEE/ACM Transactions on Audio, Speech, and Language Processing}}, keywords = {{Continuous Speech Separation, Source Separation, Graph-PIT, Dynamic Programming, Permutation Invariant Training}}, pages = {{576--589}}, publisher = {{Institute of Electrical and Electronics Engineers (IEEE)}}, title = {{{Segment-Less Continuous Speech Separation of Meetings: Training and Evaluation Criteria}}}, doi = {{10.1109/taslp.2022.3228629}}, volume = {{31}}, year = {{2023}}, } @article{49634, author = {{Ruiz Alvarado, Isaac Azahel and Zare Pour, Mohammad Amin and Hannappel, Thomas and Schmidt, Wolf Gero}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{4}}, publisher = {{American Physical Society (APS)}}, title = {{{Structural fingerprints in the reflectance anisotropy of AlInP(001)}}}, doi = {{10.1103/physrevb.108.045410}}, volume = {{108}}, year = {{2023}}, } @article{48599, abstract = {{AbstractThe biexciton‐exciton emission cascade commonly used in quantum‐dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work, it focuses on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishability. It achieves this goal by selectively reducing the biexciton lifetime with an optical resonator. It demonstrates that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and twofold degenerate optical modes. The in‐depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum‐dot cavity excitation dynamics with full access to photon properties. It reports non‐trivial dependencies on system parameters and use the predictive power of the combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values, here specifically for the telecom C‐band at 1550 nm.}}, author = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}}, issn = {{2511-9044}}, journal = {{Advanced Quantum Technologies}}, keywords = {{tet_topic_qd}}, publisher = {{Wiley}}, title = {{{On‐Demand Indistinguishable and Entangled Photons Using Tailored Cavity Designs}}}, doi = {{10.1002/qute.202300142}}, year = {{2023}}, } @unpublished{43246, abstract = {{The biexciton-exciton emission cascade commonly used in quantum-dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work we focus on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishibility. We achieve this goal by selectively reducing the biexciton lifetime with an optical resonator. We demonstrate that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and two-fold degenerate optical modes. Our in-depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum-dot cavity excitation dynamics with full access to photon properties. We report non-trivial dependencies on system parameters and use the predictive power of our combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values in the telecom C-band at $1550\,\mathrm{nm}$.}}, author = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}}, keywords = {{tet_topic_phc, tet_topic_qd}}, title = {{{On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs}}}, year = {{2023}}, } @unpublished{50172, abstract = {{Viscous hydrodynamics serves as a successful mesoscopic description of the Quark-Gluon Plasma produced in relativistic heavy-ion collisions. In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the hydrodynamic and non-hydrodynamic modes of linear response in the sound channel from a first-principle calculation in kinetic theory. We do this with a new approach wherein we discretize the collision kernel to directly calculate eigenvalues and eigenmodes of the evolution operator. This allows us to study the Green's functions at any point in the complex frequency space. Our study focuses on scalar theory with quartic interaction and we find that the analytic structure of Green's functions in the complex plane is far more complicated than just poles or cuts which is a first step towards an equivalent study in QCD kinetic theory.}}, author = {{Ochsenfeld, Stephan and Schlichting, Sören}}, booktitle = {{arXiv:2308.04491}}, title = {{{Hydrodynamic and Non-hydrodynamic Excitations in Kinetic Theory -- A Numerical Analysis in Scalar Field Theory}}}, year = {{2023}}, } @unpublished{50221, abstract = {{Memory Gym presents a suite of 2D partially observable environments, namely Mortar Mayhem, Mystery Path, and Searing Spotlights, designed to benchmark memory capabilities in decision-making agents. These environments, originally with finite tasks, are expanded into innovative, endless formats, mirroring the escalating challenges of cumulative memory games such as ``I packed my bag''. This progression in task design shifts the focus from merely assessing sample efficiency to also probing the levels of memory effectiveness in dynamic, prolonged scenarios. To address the gap in available memory-based Deep Reinforcement Learning baselines, we introduce an implementation that integrates Transformer-XL (TrXL) with Proximal Policy Optimization. This approach utilizes TrXL as a form of episodic memory, employing a sliding window technique. Our comparative study between the Gated Recurrent Unit (GRU) and TrXL reveals varied performances across different settings. TrXL, on the finite environments, demonstrates superior sample efficiency in Mystery Path and outperforms in Mortar Mayhem. However, GRU is more efficient on Searing Spotlights. Most notably, in all endless tasks, GRU makes a remarkable resurgence, consistently outperforming TrXL by significant margins. Website and Source Code: https://github.com/MarcoMeter/endless-memory-gym/}}, author = {{Pleines, Marco and Pallasch, Matthias and Zimmer, Frank and Preuss, Mike}}, booktitle = {{arXiv:2309.17207}}, title = {{{Memory Gym: Towards Endless Tasks to Benchmark Memory Capabilities of Agents}}}, year = {{2023}}, } @unpublished{50147, abstract = {{Many materials processes and properties depend on the anisotropy of the energy of grain boundaries, i.e.~on the fact that this energy is a function of the five geometric degrees of freedom (DOF) of the interface. To access this parameter space in an efficient way and to discover energy cusps in unexplored regions, a method was recently established, which combines atomistic simulations with statistical methods 10.1002/adts.202100615. This sequential sampling technique is now extended in the spirit of an active learning algorithm by adding a criterion to decide when the sampling has advanced enough to stop. In this instance, two parameters to analyse the sampling results on the fly are introduced: the number of cusps, which correspond to the most interesting and important regions of the energy landscape, and the maximum change of energy between two sequential iterations. Monitoring these two quantities provides valuable insight into how the subspaces are energetically structured. The combination of both parameters provides the necessary information to evaluate the sampling of the 2D subspaces of grain boundary plane inclinations of even non-periodic, low angle grain boundaries. With a reasonable number of data points in the initial design, only a few appropriately chosen sequential iterations already improve the accuracy of the sampling substantially and unknown cusps can be found within a few additional sequential steps.}}, author = {{Schmalofski, Timo and Kroll, Martin and Dette, Holger and Janisch, Rebecca}}, booktitle = {{arXiv:2302.01603}}, title = {{{Towards active learning: A stopping criterion for the sequential sampling of grain boundary degrees of freedom}}}, year = {{2023}}, }