Shaping the Hamiltonian of many-body spin systems on a Rydberg-atom quantum simulator - How periodic driving and spin-encoding states tune the dynamics of strongly interacting quantum systems

Quantum simulation enables the experimental investigation of simplified physical models that capture the fundamental aspects of complex quantum many-body systems. In order to understand how interaction parameters impact the macroscopic properties of the system, it is essential to modify the Hamiltonian in a controlled fashion. This thesis presents novel approaches to perform tunable quantum simulations in an isolated many-body spin-1/2 system represented by dipolar interacting Rydberg atoms. These approaches are employed to study out-of-equilibrium dynamics in different regimes. The four major achievements are as follows: (i) Using various spin-encoding states within the Rydberg manifold, we realize XX, XXZ, and Ising models with spatial disorder and study magnetization relaxation dynamics. We identify a universal behavior that is independent of the microscopic properties and explained by the emergence of effective spin pairs. (ii) To introduce new effective interactions into the system, we employ a time-periodic drive to transform the natural dipolar interaction Hamiltonian into a desired target form. This method, known as Floquet engineering, is validated using both a gas of Rydberg atoms and individually trapped Rydberg atoms. We demonstrate its potential for tunable quantum simulation of Heisenberg spin models by altering symmetry and transport properties. (iii) Combining the methods developed in (i) and (ii), we devise and implement a time reversal protocol. The versatility of the approach is demonstrated by reversing quantum dynamics for a variety of many-body Hamiltonian with tunable symmetry, which we realize through Floquet engineering. (iv) Beyond experimental demonstration, we propose alternative approaches to engineer many-body systems, including a new approach to realize time-reversal operations, and an approach for introducing mobile dopants into Ryderg spin systems. The Hamiltonian engineering methods can be directly applied to further study the extend to which the emergence of effective spin pairs is the common feature of disordered quantum spin systems. In general, engineering a wide range of Hamiltonians opens up several new opportunities for investigating fields that range from spin transport and spin glasses to quantum thermalization

2-Undecanone : a new attractant for anthropophilic mosquitoes

Stechmücken der Art Stegomyia aegypti (ehemals Aedes aegypti, REINERT et al. 2004) sind die wichtigsten Überträger von Gelbfieber- und Dengueviren. Diverse Arten der Gattung Anopheles verbreiten die Erreger der Malaria. Bei Versuchen, Malaria, Gelbfieber und Dengue einzudämmen, wurden in den letzten Jahrzehnten wiederholt Kampagnen gegen Stechmücken geführt. Dabei wurden Insektizide vielfach flächendeckend ausgebracht. Dies führte kurzfristig zu geringeren Mückendichten, allerdings entwickelten sich auch vielerorts gegen diese Gifte resistente Mückenpopulationen. Anstelle des flächendeckenden Gifteinsatzes wird heute versucht, die Insektizide örtlich und zeitlich effektiv einzusetzen, um so die Gefahr weiterer Resistenzbildung zu minimieren und sowohl die Kosten als auch die Belastung für Umwelt und Bevölkerung möglichst gering zu halten. Um Insektizide zur richtigen Zeit gezielt ausbringen zu können, ist ein Monitoring der Mücken erforderlich. Mückenfallen, die durch optische Effekte und Duftstoffe gezielt anthropophile Stechmückenarten anlocken, sind für ein derartiges Bestandsmonitoring besonders geeignet. Auf der Suche nach attraktiven Duftstoffen, welche die Effektivität solcher Fallen erhöhen, wurde unter anderem auch 2-Undecanon getestet. In Verhaltensversuchen mit den anthropophilen Mückenarten Stegomyia aegypti und Anopheles stephensi konnte die Attraktivität dieser Substanz sowohl als Einzelreiz als auch in Kombination mit anderen Attraktanzien gezeigt und quantifiziert werden.The attractiveness of 2-undecanone to host-seeking female Stegomyia aegpyti (former Aedes aegypti) and female Anopheles stephensi (Diptera: Culicidae) mosquitoes was tested in a Y-tube bioassay under laboratory conditions. -Undecanone alone in a concentration of 40 ppm was significantly more attractive to S. aegypti mosquitoes than pure air. In combination with other kairomones such as caproic acid, lactic acid and ammonia doses of 2-undecanone from 4 ppm up to 130 ppm augmented significantly the attractiveness of these kairomones. The synergism of 2-undecanone with other attractants is comparable to that one described for lactic acid. The combination of 2-undecanone with lactic acid, however, was more attractive than the two compounds as single stimuli. Interestingly 2-undecanone is neither known as an human skin compound nor as a volatile in human breath. First field experiments near Regensburg in Germany with BG-Sentinel® mosquito traps could not confirm the attractive effect of 2-undecanone (ROSE et al. 2006) for Culex species. A possible explanation could be that the tested dose of 2-undecanone was not in the optimum range or that the studied species do not respond to this compound

Actuation mechanisms of carbon nanotube-based architectures

State of the art smart materials such as piezo ceramics or electroactive polymers cannot feature both, mechanical stiffness and high active strain. Moreover, properties like low density, high mechanical stiffness and high strain at the same time driven by low energy play an increasingly important role for their future application. Carbon nanotubes (CNT), show this behavior. Their active behavior was observed 1999 the first time using paper-like mats made of CNT. Therefore the CNT-papers are electrical charged within an electrolyte thus forming a doublelayer. The measured deflection of CNT material is based on the interaction between the charged high surface area formed by carbon nanotubes and ions provided by the electrolyte. Although CNT-papers have been extensively analyzed as well at the macro-scale as nano-scale there is still no generally accepted theory for the actuation mechanism. This paper focuses on investigations of the actuation mechanisms of CNT-papers in comparison to vertically aligned CNT-arrays. One reason of divergent results found in literature might be attributed to different types of CNT samples. While CNT-papers represent architectures of short CNTs which need to bridge each other to form the dimensions of the sample, the continuous CNTs of the array feature a length of almost 3 mm, along which the experiments are carried out. Both sample types are tested within an actuated tensile test set-up under different conditions. While the CNT-papers are tested in water-based electrolytes with comparably small redox-windows the hydrophobic CNT-arrays are tested in ionic liquids with comparatively larger redox-ranges. Furthermore an in-situ micro tensile test within an SEM is carried out to prove the optimized orientation of the MWCNTs as result of external load. It was found that the performance of CNT-papers strongly depends on the test conditions. However, the CNT-arrays are almost unaffected by the conditions showing active response at negative and positive voltages. A micro alignment as result of tensile stress can be proven. A comparison of both results point out that the actuation mechanism strongly depends on the weakest bonds of the architectures: Van-der-Waals-bonds vs. covalent C-bond

Gibt Keimen keine Chance - Verbundoberflächen mit antimikrobiellen Eigenschaften

Der globale Flugverkehr ist ein stark expansiver Wirtschaftszweig, der sowohl der Luftfahrtindustrie als auch der Tourismusbranche hohe Umsätze ermöglicht. Die Angst vor der Verbreitung des Corona-Virus hat jedoch seit Beginn 2020 z. B. den innerdeutschen Flugverkehr zeitweise um bis zu 75% zurückgehen lassen. Konzepte zur Reduzierung der Keimlast sind zwingend erforderlich. Tatsächlich finden sich im Flugzeug auf den ausklappbaren Tischen und den Sanitäranlagen die größten Keimbelastungen. Um dieses Risiko auch für zukünftige Pandemien zu reduzieren, beschäftigen sich das DLR-Projekt Keimfreies Fliegen und das Luftfahrtforschungsprogramm-Projekt FIONA (Funktions-Integrierte Optimierte Neuartige Additive Strukturen) mit antimikrobiellen Oberflächen. Neben der aerosolbasierten Übertragung mittels kleinster Tröpfchen in der Atemluft, die erfolgreich mit Masken und Luftfiltern reduziert werden kann, liegt der Fokus bei den hier vorgestellten Projekten auf biologischen Oberflächenfilmen und deren energieeffiziente, schneller und dauerhafter Neutralisierung. Dabei soll einerseits mit Faserverbundoberflächen gearbeitet werden, in die antimikrobielle Materialien eingebettet wurden und die gleichzeitig auch thermisch aktiviert werden können. Andererseits wird die Herstellung antimikrobieller Oberflächen durch 3D-Druck untersucht. Die große Designfreiheit der additiven Fertigungstechnologie erlaubt eine schnelle Herstellung funktionsintegrierter Multimaterialbauteile, sodass für die Airlines eine wirtschaftliche Nachrüstung mit antimikrobiellen Kabinenbauteilen möglich ist

Experimental and finite element analyses of multifunctional skins for morphing wing applications

As a consequence of operational efficiency because of rising energy costs, future transport systems need to be mission-adaptive. Especially in aircraft design the limits of lightweight construction, reduced aerodynamic drag and optimized propulsion are pushed further and further. The first two aspects can be addressed by using a morphing leading edge. Great economic advantages can be expected as a result of gapless surfaces which feature longer areas of laminar flow. Instead of focusing on the kinematics, which are already published in a great number of varieties, this paper emphasizes as major challenge, the qualification of a multi-material layup which meets the compromise of needed stiffness, flexibility and essential functions to match the flight worthiness requirements, such as erosion shielding, impact safety, lighting protection and de-icing. It is the aim to develop an gapless leading edge device and to prepare the path for higher technology readiness levels resulting in an airborne application. During several national and European projects the DLR developed a gapless smart droop nose concept, which functionality was successfully demonstrated using a two-dimensional 5 m in span prototype in low speed (up to 50 m/s) wind tunnel tests. The basic structure is made of commercially available and certified glass-fiber reinforced plastics (GFRP, Hexcel Hexply 913). This paper presents 4-point bending tests to characterize the composite with its integrated functions. The integrity and aging/fatigue issues of different material combinations are analyzed by experiments. It can be demonstrated that only by adding functional layers the mentioned requirements such as erosion-shielding or de-icing can be satisfied. The total thickness of the composite skin increases by more than 100 % when required functions are integrated as additional layers. This fact has a tremendous impact on the maximum strain of the outer surface if it features a complete monolithic build-up. Based on experimental results a numerical model can be set up for further structural optimizaton of the multi-functional laminate. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Structure-Integrated Thin-Film Supercapacitor as a Sensor

Today, aircraft composite structures are generally over-dimensioned to avoid catastrophic failure by unseen damages. This leads to a higher system weight and therefore an unwanted increase in greenhouse gas emissions. To reduce this parasitic mass, load monitoring can play an important role in damage detection. Additionally, the weight and volume of future aircraft structures can also be reduced by energy storing and load carrying structures: so-called power composites. In this study a novel method of combining both approaches for maximum weight reduction is shown. This is achieved by using power composites as load monitoring sensors and energy suppliers. Therefore, supercapacitors are integrated into fiber reinforced polymers and are then used to investigate the mechanical load influence. By using four-point bending experiments and in situ electrochemical impedance spectroscopy, a strong relation between the mechanical load and the electrochemical system is found and analyzed using a model. For the first time, it is possible to detect small strain values down to 0.2% with a power composite. This strain is considerably lower than the conventional system load. The developed model and the impedance data indicate the possibility of using the composite as an energy storage as well as a strain sensor

Observation of universal relaxation dynamics in disordered quantum spin systems

A major goal toward understanding far-from-equilibrium dynamics of quantum many-body systems consists in finding indications of universality in the sense that the dynamics no longer depends on microscopic details of the system. We realize a large range of many-body spin systems on a Rydberg atom quantum simulator by choosing appropriate Rydberg state combinations. We use this platform to compare the magnetization relaxation dynamics of disordered Heisenberg XX-, XXZ- and Ising Hamiltonians in a scalable fashion. After appropriate rescaling of evolution time, the dynamics collapse onto a single curve. We find that the observed universal behavior is captured by theoretical models that only consider local pairs of spins. Associated to each pair is a local quasi-conserved quantity, allowing us to describe the early time dynamics of the system in terms of an integrable model similar to systems featuring prethermalization. Since the dynamics of pairs are independent of the type of Hamiltonian up to a scaling factor, this integrable model explains the observed universal relaxation dynamics of disordered Heisenberg quantum spin systems