Superconducting quantum circuits for hybrid architectures

Im Bestreben nach neuen Quantentechnologien gehören supraleitende Quantenschaltkreise (SQS) zu den weltweit führenden Hardware-Plattformen, und finden bereits Anwendung in den Bereichen der Quanteninformationsverarbeitung, Quantenkommunikation und –kryptographie, sowie in der Quantensensorik. Obwohl die Kohärenz solcher Schaltkreise in den vergangenen zwei Jahrzehnten enorm gesteigert werden konnte, existieren konkurrierende Plattformen, die teilweise in bedeutenden Aspekten noch immer überlegen sind. Gerade deshalb erscheint eine Verknüpfung unterschiedlicher Implementierungen zu einer Quantenhybridarchitektur reizvoll, mit dem Ziel, die Stärken der individuellen Plattformen zu kombinieren und gleichzeitig vorhandene Schwächen auszugleichen. In diesem Zusammenhang habe ich im Rahmen meiner Dissertation eine nichtlineare Induktivität für die Verwendung in SQSs entwickelt, die, basierend auf dem ungeordneten Supraleiter „granulares Aluminium“ (grAl), auch in hohen Magnetfeldern verwendet werden kann, was eine Grundvoraussetzung für die Anwendbarkeit in Hybridstrukturen darstellt. Als Machbarkeitsnachweise habe ich den konventionellen Josephson-Kontakt in einem Transmon-Qubit mit dieser grAl-Induktivität ausgetauscht, und die Mikrowelleneigenschaften des Systems im Magnetfeld charakterisiert. Um das Signal-Rausch-Verhältnis der Messung zu verbessern, habe ich zudem einen nicht-entarteten parametrischen Verstärker entwickelt, der auf langen Ketten von Josephson-Kontakten basiert. Die Neuheit des zugrundeliegenden Konzeptes ist dabei die Verwendung von mehreren Eigenmodpaaren der Josephson-Kette, um den Frequenzbereich zwischen 1 und 10 GHz möglichst mit einem einzigen Verstärker abzudecken

A case study evaluating the ergonomic and productivity impacts of partial automation strategies in the electronics industry

A case study is presented that evaluates the impact of partial automation strategies on productivity and ergonomics. A company partly automated its assembly and transportation functions while moving from a parallel-batch to a serial line-based production system. Data obtained from company records and key informants were combined with detailed video analysis, biomechanical modelling data and field observations of the system. The new line system was observed to have 51% higher production volumes with 21% less per product labour input and lower work-in-process levels than the old batch-cart system. Partial automation of assembly operations was seen to reduce the total repetitive assembly work at the system level by 34%. Automation of transportation reduced transport labour by 63%. The strategic decision to implement line-transportation was found to increase movement repetitiveness for operators at manual assembly stations, even though workstations were constructed with consideration to ergonomics. Average shoulder elevation at these stations increased 30% and average shoulder moment increased 14%. It is concluded that strategic decisions made by designers and managers early in the production system design phase have considerable impact on ergonomic conditions in the resulting system. Automation of transport and assembly both lead to increased productivity, but only elements related to the automatic line system also increased mechanical loads on operators and hence increased the risk for work-related disorders. Suggestions for integrating the consideration of ergonomics into production system design are made

Ballistic aggregation for one-sided Brownian initial velocity

We study the one-dimensional ballistic aggregation process in the continuum limit for one-sided Brownian initial velocity (i.e. particles merge when they collide and move freely between collisions, and in the continuum limit the initial velocity on the right side is a Brownian motion that starts from the origin $x=0$). We consider the cases where the left side is either at rest or empty at $t=0$. We derive explicit expressions for the velocity distribution and the mean density and current profiles built by this out-of-equilibrium system. We find that on the right side the mean density remains constant whereas the mean current is uniform and grows linearly with time. All quantities show an exponential decay on the far left. We also obtain the properties of the leftmost cluster that travels towards the left. We find that in both cases relevant lengths and masses scale as $t^2$ and the evolution is self-similar.Comment: 18 pages, published in Physica

Onset of phase diffusion in high kinetic inductance granular aluminum micro-SQUIDs

Superconducting granular aluminum is attracting increasing interest due to its high kinetic inductance and low dissipation, favoring its use in kinetic inductance particle detectors, superconducting resonators or quantum bits. We perform switching current measurements on DC-SQUIDs, obtained by introducing two identical geometric constrictions in granular aluminum rings of various normal-state resistivities in the range from ρ n = 250–5550 μΩ cm. The relative high kinetic inductance of the SQUID loop, in the range of tens of nH, leads to a suppression of the modulation in the measured switching current versus magnetic flux, accompanied by a distortion towards a triangular shape. We observe a change in the temperature dependence of the switching current histograms with increasing normal-state film resistivity. This behavior suggests the onset of a diffusive motion of the superconducting phase across the constrictions in the two-dimensional washboard potential of the SQUIDs, which could be caused by a change of the local electromagnetic environment of films with increasing normal-state resistivities

Influence of the Available Surface Area and Cell Elasticity on Bacterial Adhesion Forces on Highly Ordered Silicon Nanopillars

[Image: see text] Initial bacterial adhesion to solid surfaces is influenced by a multitude of different factors, e.g., roughness and stiffness, topography on the micro- and nanolevel, as well as chemical composition and wettability. Understanding the specific influences and possible interactive effects of all of these factors individually could lead to guidance on bacterial adhesion and prevention of unfavorable consequences like medically relevant biofilm formation. On this way, the aim of the present study was to identify the specific influence of the available surface area on the adhesion of clinically relevant bacterial strains with different membrane properties: Gram-positive Staphylococcus aureus and Gram-negative Aggregatibacter actinomycetemcomitans. As model surfaces, silicon nanopillar specimens with different spacings were fabricated using electron beam lithography and cryo-based reactive ion etching techniques. Characterization by scanning electron microscopy and contact angle measurement revealed almost defect-free highly ordered nanotopographies only varying in the available surface area. Bacterial adhesion forces to these specimens were quantified by means of single-cell force spectroscopy exploiting an atomic force microscope connected to a microfluidic setup (FluidFM). The nanotopographical features reduced bacterial adhesion strength by reducing the available surface area. In addition, the strain-specific interaction in detail depended on the bacterial cell’s elasticity and deformability as well. Analyzed by confocal laser scanning microscopy, the obtained results on bacterial adhesion forces could be linked to the subsequent biofilm formation on the different topographies. By combining two cutting-edge technologies, it could be demonstrated that the overall bacterial adhesion strength is influenced by both the simple physical interaction with the underlying nanotopography and its available surface area as well as the deformability of the cell