Transformation optics: a tool to reveal and make use of symmetries in plasmonics

Symmetries are omnipresent in physics. From classical mechanics, via solid state physics to particle physics, symmetries provide a means for classification and often lead to deep physical insight. In this thesis, we study symmetries in plasmonics using Transformation optics. We show how Transformation optics can be used to reveal, study and make us of symmetries in practical calculations, by studying a range of plasmonic systems. First, we show that an ellipse and spheroids possess a `hidden' rotational symmetry that becomes apparent when transforming them to a rotationally symmetric structure. Next, we investigate plasmonic gratings and show that a whole class of plasmonic gratings (and other periodic structures) can be related to a translationally invariant slab, thereby inheriting all the slabs spectral properties. In studying the plasmonic grating, we extend the Transformation optics approach to treat periodic systems with extent larger than the wavelength in one direction. Finally, we use Transformation optics to study electron energy loss spectroscopy and cathodoluminescence problems in plasmonics, by mapping the plasmonic nanoparticles under investigation to more symmetric ones. Thus, again using the symmetry of the transformed structures to derive analytical solutions to the problem at hand.Open Acces

Noise assisted transport in the Wannier-Stark system

We investigated how the presence of an additional lattice potential, driven by a harmonic noise process, changes the transition rate from the ground band to the first excited band in a Wannier-Stark system. Alongside numerical simulations, we present two models that capture the essential features of the dynamics. The first model uses a noise-driven Landau-Zener approximation and describes the short time evolution of the full system very well. The second model assumes that the noise process' correlation time is much larger than the internal timescale of the system, yet it allows for good estimates of the observed transition rates and gives a simple interpretation of the dynamics. One of the central results is that we obtain a way to control the interband transitions with the help of the second lattice. This could readily be realized in state-of-the-art experiments using either Bose-Einstein condensates or optical pulses in engineered potentials

Dimensioning Microgrids for Productive Use of Energy in the Global South—Considering Demand Side Flexibility to Reduce the Cost of Energy

Microgrids using renewable energy sources play an important role in providing universal electricity access in rural areas in the Global South. Current methods of system dimensioning rely on stochastic load profile modeling, which has limitations in microgrids with industrial consumers due to high demand side uncertainties. In this paper, we propose an alternative approach considering demand side management during system design which we implemented using a genetic scheduling algorithm. The developed method is applied to a test case system on Idjwi Island, Democratic Republic of the Congo (DRC), which is to be powered by a micro hydropower plant (MHP) in combination with a photovoltaic (PV) system and a battery energy storage system (BESS). The results show that the increased flexibility of industrial consumers can significantly reduce the cost of electricity. Most importantly, the presented method quantifies the trade-off between electricity cost and consumer flexibility. This gives local stakeholders the ability to make an informed compromise and design an off-grid system that covers their electricity needs in the most cost-efficient way

Standardised documentation of instrument use during laparoscopic surgery

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.To date, usability problems for laparoscopic instruments have mainly been investigated using questionnaires or laboratory studies. However, this methodology prevents the duration and frequency of instrument use from being documented objectively. Therefore, a tablet was used to create a graphic user interface which enables instrument use by operating and assisting surgeons to be documented with a high level of temporal precision. In a preliminary study, instrument use was documented for five laparoscopic operations (0:44h-6:01h). 2021 actions and 221 changes of instruments were documented. The longest uninterrupted usage period without changing hands was determined for grasping forceps at 97 min

Transformations of Stabilizer States in Quantum Networks

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 mathematical framework to study PLC equivalence of stabilizer states, relating it to the classification of tuples of bilinear forms. 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. {\bf 47}, 062106~(2006)], we show that for $4$ and more parties it is an infinite set, even when considering party-local unitary transformations. Moreover, we explicitly compute the EGS for $4$ parties up to $10$ qubits. Finally, we generalize the framework to qudit stabilizer states in prime dimensions not equal to $2$, which allows us to show that the decomposition of qudit stabilizer states into states from the EGS is unique.Comment: 37 pages, 7 figures, final versio

High-resolution real-world electricity data from three microgrids in the global south

Microgrids are a promising solution for providing renewable electricity access to rural populations in the Global South. To ensure such renewable microgrids are affordable, careful planning and dimensioning are required. High-resolution data on electricity generation and consumption is necessary for optimal design. Unfortunately, real-world electricity data for microgrids in the Global South is scarce, and the limited data that is available has a low temporal resolution. Therefore, in this paper, we introduce a unique high-resolution real-world electricity data set from three micro-grids in the Democratic Republic of the Congo, Rwanda, and Haiti. The data has a temporal resolution of up to five seconds and focuses on microgrids with renewable generation from either hydropower or photovoltaic systems. Furthermore, we include data from both residential and industrial microgrids. We describe the recorded data and highlight the advantages of the high resolution. We demonstrate how this resolution offers insight into consumption patterns and enables the analysis of grid voltage and frequency, which is highly relevant for the planning and dimensioning of affordable renewable microgrids in the Global South

High-Resolution Real-World Electricity Data from Three Microgrids in the Global South

Microgrids are a promising solution for providing renewable electricity access to rural populations in the Global South. To ensure such renewable microgrids are affordable, careful planning and dimensioning are required. High-resolution data on electricity generation and consumption is necessary for optimal design. Unfortunately, real-world electricity data for microgrids in the Global South is scarce, and the little data that is available has a low temporal resolution. Therefore, in this paper, we introduce a unique highresolution real-world electricity data set from three microgrids in the Democratic Republic of the Congo, Rwanda, and Haiti. The data has a temporal resolution of up to five seconds and focuses on microgrids with renewable generation from either hydropower or photovoltaic systems. Furthermore, we include data from both residential and industrial microgrids. We describe the recorded data and highlight the advantages of the high resolution. We demonstrate how this resolution offers insight into consumption patterns and enables the analysis of grid voltage and frequency, which is highly relevant for the planning and dimensioning of affordable renewable microgrids in the Global South