@inproceedings{29220, abstract = {{Modern services often comprise several components, such as chained virtual network functions, microservices, or machine learning functions. Providing such services requires to decide how often to instantiate each component, where to place these instances in the network, how to chain them and route traffic through them. To overcome limitations of conventional, hardwired heuristics, deep reinforcement learning (DRL) approaches for self-learning network and service management have emerged recently. These model-free DRL approaches are more flexible but typically learn tabula rasa, i.e., disregard existing understanding of networks, services, and their coordination. Instead, we propose FutureCoord, a novel model-based AI approach that leverages existing understanding of networks and services for more efficient and effective coordination without time-intensive training. FutureCoord combines Monte Carlo Tree Search with a stochastic traffic model. This allows FutureCoord to estimate the impact of future incoming traffic and effectively optimize long-term effects, taking fluctuating demand and Quality of Service (QoS) requirements into account. Our extensive evaluation based on real-world network topologies, services, and traffic traces indicates that FutureCoord clearly outperforms state-of-the-art model-free and model-based approaches with up to 51% higher flow success ratios.}}, author = {{Werner, Stefan and Schneider, Stefan Balthasar and Karl, Holger}}, booktitle = {{IEEE/IFIP Network Operations and Management Symposium (NOMS)}}, keywords = {{network management, service management, AI, Monte Carlo Tree Search, model-based, QoS}}, location = {{Budapest}}, publisher = {{IEEE}}, title = {{{Use What You Know: Network and Service Coordination Beyond Certainty}}}, year = {{2022}}, } @phdthesis{29763, abstract = {{Modern-day communication has become more and more digital. While this comes with many advantages such as a more efficient economy, it has also created more and more opportunities for various adversaries to manipulate communication or eavesdrop on it. The Snowden revelations in 2013 further highlighted the seriousness of these threats. To protect the communication of people, companies, and states from such threats, we require cryptography with strong security guarantees. Different applications may require different security properties from cryptographic schemes. For most applications, however, so-called adaptive security is considered a reasonable minimal requirement of security. Cryptographic schemes with adaptive security remain secure in the presence of an adversary that can corrupt communication partners to respond to messages of the adversaries choice, while the adversary may choose the messages based on previously observed interactions. While cryptography is associated the most with encryption, this is only one of many primitives that are essential for the security of digital interactions. This thesis presents novel identity-based encryption (IBE) schemes and verifiable random functions (VRFs) that achieve adaptive security as outlined above. Moreover, the cryptographic schemes presented in this thesis are proven secure in the standard model. That is without making use of idealized models like the random oracle model.}}, author = {{Niehues, David}}, keywords = {{public-key cryptography, lattices, pairings, verifiable random functions, identity-based encryption}}, title = {{{More Efficient Techniques for Adaptively-Secure Cryptography}}}, doi = {{10.25926/rdtq-jw45}}, year = {{2022}}, } @article{31241, author = {{Verma, A.K. and Bopp, F. and Finley, J.J. and Jonas, B. and Zrenner, A. and Reuter, Dirk}}, issn = {{0022-0248}}, journal = {{Journal of Crystal Growth}}, keywords = {{Materials Chemistry, Inorganic Chemistry, Condensed Matter Physics}}, publisher = {{Elsevier BV}}, title = {{{Low Areal Densities of InAs Quantum Dots on GaAs(100) Prepared by Molecular Beam Epitaxy}}}, doi = {{10.1016/j.jcrysgro.2022.126715}}, year = {{2022}}, } @article{31480, abstract = {{Optical geometric phase encoded by in-plane spatial orientation of microstructures has promoted the rapid development of numerous functional meta-devices. However, pushing the concept of the geometric phase toward the acoustic community still faces challenges. In this work, we utilize two acoustic nonlocal metagratings that could support a direct conversion between an acoustic plane wave and a designated vortex mode to obtain the acoustic geometric phase, in which an orbital angular momentum conversion process plays a vital role. In addition, we realize the acoustic geometric phases of different orders by merely varying the orientation angle of the acoustic nonlocal metagratings. Intriguingly, according to our developed theory, we reveal that the reflective acoustic geometric phase, which is twice the transmissive one, can be readily realized by transferring the transmitted configuration to a reflected one. Both the theoretical study and experimental measurements verify the announced transmissive and reflective acoustic geometric phases. Moreover, the reconfigurability and continuous phase modulation that covers the 2π range shown by the acoustic geometric phases provide us with the alternatives in advanced acoustic wavefront control.}}, author = {{Liu, Bingyi and Zhou, Zhiling and Wang, Yongtian and Zentgraf, Thomas and Li, Yong and Huang, Lingling}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{21}}, publisher = {{AIP Publishing}}, title = {{{Experimental verification of the acoustic geometric phase}}}, doi = {{10.1063/5.0091474}}, volume = {{120}}, year = {{2022}}, } @article{31541, author = {{Kobecki, Michal and Scherbakov, Alexey V. and Kukhtaruk, Serhii M. and Yaremkevich, Dmytro D. and Henksmeier, Tobias and Trapp, Alexander and Reuter, Dirk and Gusev, Vitalyi E. and Akimov, Andrey V. and Bayer, Manfred}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, keywords = {{General Physics and Astronomy}}, number = {{15}}, publisher = {{American Physical Society (APS)}}, title = {{{Giant Photoelasticity of Polaritons for Detection of Coherent Phonons in a Superlattice with Quantum Sensitivity}}}, doi = {{10.1103/physrevlett.128.157401}}, volume = {{128}}, year = {{2022}}, } @article{33264, abstract = {{We investigate bifurcations in feedforward coupled cell networks. Feedforward structure (the absence of feedback) can be defined by a partial order on the cells. We use this property to study generic one-parameter steady state bifurcations for such networks. Branching solutions and their asymptotics are described in terms of Taylor coefficients of the internal dynamics. They can be determined via an algorithm that only exploits the network structure. Similar to previous results on feedforward chains, we observe amplifications of the growth rates of steady state branches induced by the feedforward structure. However, contrary to these earlier results, as the interaction scenarios can be more complicated in general feedforward networks, different branching patterns and different amplifications can occur for different regions in the space of Taylor coefficients.}}, author = {{von der Gracht, Sören and Nijholt, Eddie and Rink, Bob}}, issn = {{0951-7715}}, journal = {{Nonlinearity}}, keywords = {{Applied Mathematics, General Physics and Astronomy, Mathematical Physics, Statistical and Nonlinear Physics}}, number = {{4}}, pages = {{2073--2120}}, publisher = {{IOP Publishing}}, title = {{{Amplified steady state bifurcations in feedforward networks}}}, doi = {{10.1088/1361-6544/ac5463}}, volume = {{35}}, year = {{2022}}, } @article{33332, author = {{Bopp, Frederik and Rojas, Jonathan and Revenga, Natalia and Riedl, Hubert and Sbresny, Friedrich and Boos, Katarina and Simmet, Tobias and Ahmadi, Arash and Gershoni, David and Kasprzak, Jacek and Ludwig, Arne and Reitzenstein, Stephan and Wieck, Andreas and Reuter, Dirk and Müller, Kai and Finley, Jonathan J.}}, issn = {{2511-9044}}, journal = {{Advanced Quantum Technologies}}, keywords = {{Electrical and Electronic Engineering, Computational Theory and Mathematics, Condensed Matter Physics, Mathematical Physics, Nuclear and High Energy Physics, Electronic, Optical and Magnetic Materials, Statistical and Nonlinear Physics}}, publisher = {{Wiley}}, title = {{{Quantum Dot Molecule Devices with Optical Control of Charge Status and Electronic Control of Coupling}}}, doi = {{10.1002/qute.202200049}}, year = {{2022}}, } @article{33682, author = {{Khazaei, Mohammad and Ranjbar, Ahmad and Kang, Yoon‐Gu and Liang, Yunye and Khaledialidusti, Rasoul and Bae, Soungmin and Raebiger, Hannes and Wang, Vei and Han, Myung Joon and Mizoguchi, Hiroshi and Bahramy, Mohammad S. and Kühne, Thomas and Belosludov, Rodion V. and Ohno, Kaoru and Hosono, Hideo}}, issn = {{1616-301X}}, journal = {{Advanced Functional Materials}}, keywords = {{Electrochemistry, Condensed Matter Physics, Biomaterials, Electronic, Optical and Magnetic Materials}}, number = {{20}}, publisher = {{Wiley}}, title = {{{Electronic Structures of Group III–V Element Haeckelite Compounds: A Novel Family of Semiconductors, Dirac Semimetals, and Topological Insulators}}}, doi = {{10.1002/adfm.202110930}}, volume = {{32}}, year = {{2022}}, } @article{33676, author = {{Schulze Lammers, Bertram and López-Salas, Nieves and Stein Siena, Julya and Mirhosseini, Hossein and Yesilpinar, Damla and Heske, Julian Joachim and Kühne, Thomas and Fuchs, Harald and Antonietti, Markus and Mönig, Harry}}, issn = {{1936-0851}}, journal = {{ACS Nano}}, keywords = {{General Physics and Astronomy, General Engineering, General Materials Science}}, number = {{9}}, pages = {{14284--14296}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Real-Space Identification of Non-Noble Single Atomic Catalytic Sites within Metal-Coordinated Supramolecular Networks}}}, doi = {{10.1021/acsnano.2c04439}}, volume = {{16}}, year = {{2022}}, } @article{33833, author = {{Kim, Sanghoon and Pathak, Sachin and Rhim, Sonny H. and Cha, Jongin and Jekal, Soyoung and Hong, Soon Cheol and Lee, Hyun Hwi and Park, Sung‐Hun and Lee, Han‐Koo and Park, Jae‐Hoon and Lee, Soogil and Steinrück, Hans-Georg and Mehta, Apurva and Wang, Shan X. and Hong, Jongill}}, issn = {{2198-3844}}, journal = {{Advanced Science}}, keywords = {{General Physics and Astronomy, General Engineering, Biochemistry, Genetics and Molecular Biology (miscellaneous), General Materials Science, General Chemical Engineering, Medicine (miscellaneous)}}, number = {{24}}, pages = {{2201749}}, publisher = {{Wiley}}, title = {{{Giant Orbital Anisotropy with Strong Spin–Orbit Coupling Established at the Pseudomorphic Interface of the Co/Pd Superlattice}}}, doi = {{10.1002/advs.202201749}}, volume = {{9}}, year = {{2022}}, } @article{33694, abstract = {{Abstract The round robin test investigated the reliability users can expect for AlSi10Mg additive manufactured specimens by laser powder bed fusion through examining powder quality, process parameter, microstructure defects, strength and fatigue. Besides for one outlier, expected static material properties could be found. Optical microstructure inspection was beneficial to determine true porosity and porosity types to explain the occurring scatter in properties. Fractographic analyses reveal that the fatigue crack propagation starts at the rough as-built surface for all specimens. Statistical analysis of the scatter in fatigue using statistical derived safety factors concludes that at a stress of 36.87 MPa the fatigue limit of 107 cycles could be reached for all specimen with a survival probability of 99.999 %.}}, author = {{Schneider, M. and Bettge, D. and Binder, M. and Dollmeier, K. and Dreyer, Malte and Hilgenberg, K. and Klöden, B. and Schlingmann, T. and Schmidt, J.}}, issn = {{2195-8599}}, journal = {{Practical Metallography}}, keywords = {{Metals and Alloys, Mechanics of Materials, Condensed Matter Physics, Electronic, Optical and Magnetic Materials}}, number = {{10}}, pages = {{580--614}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{Reproducibility and Scattering in Additive Manufacturing: Results from a Round Robin on PBF-LB/M AlSi10Mg Alloy}}}, doi = {{10.1515/pm-2022-1018}}, volume = {{59}}, year = {{2022}}, } @article{35232, author = {{Meier, Falco and Littmann, Mario and Bürger, Julius and Riedl, Thomas and Kool, Daniel and Lindner, Jörg and Reuter, Dirk and As, Donat Josef}}, issn = {{0370-1972}}, journal = {{physica status solidi (b)}}, keywords = {{Condensed Matter Physics, Electronic, Optical and Magnetic Materials}}, publisher = {{Wiley}}, title = {{{Selective Area Growth of Cubic Gallium Nitride in Nanoscopic Silicon Dioxide Masks}}}, doi = {{10.1002/pssb.202200508}}, year = {{2022}}, } @article{34056, abstract = {{ A process sequence enabling the large-area fabrication of nanopillar-patterned semiconductor templates for selective-area heteroepitaxy is developed. Herein, the nanopillar tops surrounded by a SiNx mask film serve as nanoscale growth areas. The molecular beam epitaxial growth of InAs on such patterned GaAs[Formula: see text]A templates is investigated by means of electron microscopy. It is found that defect-free nanoscale InAs islands grow selectively on the nanopillar tops at a substrate temperature of 425 °C. High-angle annular dark-field scanning transmission electron microscopy imaging reveals that for a growth temperature of 400 °C, the InAs islands show a tendency to form wurtzite phase arms extending along the lateral [Formula: see text] directions from the central zinc blende region of the islands. This is ascribed to a temporary self-catalyzed vapor–liquid–solid growth on [Formula: see text] B facets, which leads to a kinetically induced preference for the nucleation of the wurtzite phase driven by the local, instantaneous V/III ratio, and to a concomitant reduction of surface energy of the nanoscale diameter arms. }}, author = {{Riedl, Thomas and Kunnathully, Vinay S. and Verma, Akshay Kumar and Langer, Timo and Reuter, Dirk and Büker, Björn and Hütten, Andreas and Lindner, Jörg}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{18}}, publisher = {{AIP Publishing}}, title = {{{Selective area heteroepitaxy of InAs nanostructures on nanopillar-patterned GaAs(111)A}}}, doi = {{10.1063/5.0121559}}, volume = {{132}}, year = {{2022}}, } @inproceedings{36335, abstract = {{Transformation of Fe- and Cu-rich primary phase particles was studied in an Al-Li-based alloy prepared by twin-roll casting. Thin foils for combined STEM and SEM experiments were prepared by electrolytic twin-jet polishing. They were in-situ heated in a TEM heating stage and observed at 200 kV in the JEOL JEM 2200FS electron microscope equipped with STEM HAADF and BF detectors and SEM BSE and SE detectors working both in composition and topographic modes. The resulting structures were combined with EDS mapping performed directly in the heating holder. Dissolution and transformation of Cu- and Fe-rich particles occur above 500 °C. EDS maps acquired on the foil cooled down to room temperature show that Cu and Fe are both still present in newly formed particles, most likely indicating the presence of the Al7Cu2Fe phase.}}, author = {{CIESLAR, Miroslav and KŘIVSKÁ, Barbora and KRÁLÍK, Rostislav and BAJTOŠOVÁ, Lucia and Grydin, Olexandr and STOLBCHENKO, Mykhailo and Schaper, Mirko}}, booktitle = {{METAL 2022 Conference Proeedings}}, issn = {{2694-9296}}, keywords = {{Al-Li-based alloy, in-situ TEM, homogenization, phase transformation}}, location = {{Brno}}, publisher = {{TANGER Ltd.}}, title = {{{HOMOGENIZATION OF TWIN-ROLL CAST Al-Li-BASED ALLOY STUDIED BY IN-SITU ELECTRON MICROSCOPY}}}, doi = {{10.37904/metal.2022.4438}}, year = {{2022}}, } @article{36414, abstract = {{ Recently, microcavities with anisotropic materials were shown to be able to create bands with non-zero local Berry curvature. The anisotropic refractive index of the cavity layer is believed to be critical in opening an energy gap at the tilted Dirac points. In this work, we show that the anticrossing between a cavity mode and a Bragg mode can also be realized within an empty microcavity without any birefringent materials in the cavity layer. Nondispersive bands are observed within the energy gap due to the particular refractive index distribution of the sample. The intrinsic TE-TM splitting and XY splitting of DBR mirrors induce the squeezing of the cavity modes in momentum space, so that the nondispersive bands are tilted and spin-dependent. Our results pave the way to investigate interesting physical phenomena of photonic modes close to or in the nondispersive bands without anisotropic cavity layers. }}, author = {{Gao, Ying and Li, Yao and Ma, Xuekai and Gao, Meini and Dai, Haitao and Schumacher, Stefan and Gao, Tingge}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{20}}, publisher = {{AIP Publishing}}, title = {{{Tilting nondispersive bands in an empty microcavity}}}, doi = {{10.1063/5.0093908}}, volume = {{121}}, year = {{2022}}, } @article{33671, abstract = {{Abstract We demonstrate the fabrication of micron-wide tungsten silicide superconducting nanowire single-photon detectors on a silicon substrate using laser lithography. We show saturated internal detection efficiencies with wire widths ranging from 0.59 µm to 1.43 µm under illumination at 1550 nm. We demonstrate both straight wires, as well as meandered structures. Single-photon sensitivity is shown in devices up to 4 mm in length. Laser-lithographically written devices allow for fast and easy structuring of large areas while maintaining a saturated internal efficiency for wire widths around 1 µm.}}, author = {{Protte, Maximilian and Verma, Varun B and Höpker, Jan Philipp and Mirin, Richard P and Woo Nam, Sae and Bartley, Tim}}, issn = {{0953-2048}}, journal = {{Superconductor Science and Technology}}, keywords = {{Materials Chemistry, Electrical and Electronic Engineering, Metals and Alloys, Condensed Matter Physics, Ceramics and Composites}}, number = {{5}}, publisher = {{IOP Publishing}}, title = {{{Laser-lithographically written micron-wide superconducting nanowire single-photon detectors}}}, doi = {{10.1088/1361-6668/ac5338}}, volume = {{35}}, year = {{2022}}, } @article{30342, author = {{Lange, Nina Amelie and Höpker, Jan Philipp and Ricken, Raimund and Quiring, Viktor and Eigner, Christof and Silberhorn, Christine and Bartley, Tim}}, issn = {{2334-2536}}, journal = {{Optica}}, keywords = {{Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials}}, number = {{1}}, publisher = {{The Optical Society}}, title = {{{Cryogenic integrated spontaneous parametric down-conversion}}}, doi = {{10.1364/optica.445576}}, volume = {{9}}, year = {{2022}}, } @article{33672, abstract = {{Abstract Lithium niobate is a promising platform for integrated quantum optics. In this platform, we aim to efficiently manipulate and detect quantum states by combining superconducting single photon detectors and modulators. The cryogenic operation of a superconducting single photon detector dictates the optimisation of the electro-optic modulators under the same operating conditions. To that end, we characterise a phase modulator, directional coupler, and polarisation converter at both ambient and cryogenic temperatures. The operation voltage V π / 2 of these modulators increases, due to the decrease in the electro-optic effect, by 74% for the phase modulator, 84% for the directional coupler and 35% for the polarisation converter below 8.5 K . The phase modulator preserves its broadband nature and modulates light in the characterised wavelength range. The unbiased bar state of the directional coupler changed by a wavelength shift of 85 n m while cooling the device down to 5 K . The polarisation converter uses periodic poling to phasematch the two orthogonal polarisations. The phasematched wavelength of the utilised poling changes by 112 n m when cooling to 5 K .}}, author = {{Thiele, Frederik and vom Bruch, Felix and Brockmeier, Julian and Protte, Maximilian and Hummel, Thomas and Ricken, Raimund and Quiring, Viktor and Lengeling, Sebastian and Herrmann, Harald and Eigner, Christof and Silberhorn, Christine and Bartley, Tim}}, issn = {{2515-7647}}, journal = {{Journal of Physics: Photonics}}, keywords = {{Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials}}, number = {{3}}, publisher = {{IOP Publishing}}, title = {{{Cryogenic electro-optic modulation in titanium in-diffused lithium niobate waveguides}}}, doi = {{10.1088/2515-7647/ac6c63}}, volume = {{4}}, year = {{2022}}, } @article{33673, abstract = {{ Superconducting Nanowire Single Photon Detectors (SNSPDs) have become an integral part of quantum optics in recent years because of their high performance in single photon detection. We present a method to replace the electrical input by supplying the required bias current via the photocurrent of a photodiode situated on the cold stage of the cryostat. Light is guided to the bias photodiode through an optical fiber, which enables a lower thermal conduction and galvanic isolation between room temperature and the cold stage. We show that an off-the-shelf InGaAs–InP photodiode exhibits a responsivity of at least 0.55 A/W at 0.8 K. Using this device to bias an SNSPD, we characterize the count rate dependent on the optical power incident on the photodiode. This configuration of the SNSPD and photodiode shows an expected plateau in the single photon count rate with an optical bias power on the photodiode above 6.8 µW. Furthermore, we compare the same detector under both optical and electrical bias, and show there is no significant changes in performance. This has the advantage of avoiding an electrical input cable, which reduces the latent heat load by a factor of 100 and, in principle, allows for low loss RF current supply at the cold stage. }}, author = {{Thiele, Frederik and Hummel, Thomas and Protte, Maximilian and Bartley, Tim}}, issn = {{2378-0967}}, journal = {{APL Photonics}}, keywords = {{Computer Networks and Communications, Atomic and Molecular Physics, and Optics}}, number = {{8}}, publisher = {{AIP Publishing}}, title = {{{Opto-electronic bias of a superconducting nanowire single photon detector using a cryogenic photodiode}}}, doi = {{10.1063/5.0097506}}, volume = {{7}}, year = {{2022}}, } @article{47984, abstract = {{Recent analyses by polarization resolved second-harmonic (SH) microscopy have demonstrated that ferroelectric (FE) domain walls (DWs) can possess non-Ising wall characteristics and topological nature. These analyses rely on locally analyzing the properties, directionality, and magnitude of the second-order nonlinear tensor. However, when inspecting FE DWs with SH microscopy, a manifold of different effects may contribute to the observed signal difference between domains and DWs, i.e., far-field interference, Čerenkov-type phase-matching (CSHG), and changes in the aforementioned local nonlinear optical properties. They all might be present at the same time and, therefore, require careful interpretation and separation. In this work, we demonstrate how the particularly strong Čerenkov-type contrast can selectively be blocked using dark- and bright-field SH microscopy. Based on this approach, we show that other contrast mechanisms emerge that were previously overlayed by CSHG but can now be readily selected through the appropriate experimental geometry. Using the methods presented, we show that the strength of the CSHG contrast compared to the other mechanisms is approximately 22 times higher. This work lays the foundation for the in-depth analysis of FE DW topologies by SH microscopy.}}, author = {{Hegarty, Peter A. and Beccard, Henrik and Eng, Lukas M. and Rüsing, Michael}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{24}}, publisher = {{AIP Publishing}}, title = {{{Turn all the lights off: Bright- and dark-field second-harmonic microscopy to select contrast mechanisms for ferroelectric domain walls}}}, doi = {{10.1063/5.0094988}}, volume = {{131}}, year = {{2022}}, }