Gate-tunable junctions are key elements in quantum devices based on hybrid semiconductor-superconductor materials. They serve multiple purposes ranging from tunnel spectroscopy probes to voltage-controlled qubit operations in gatemon and topological qubits. Common to all is that junction transparency plays a critical role. In this study, we grow single-crystalline InAs, InSb, and InAs1-xSbx semiconductor nanowires with epitaxial Al, Sn, and Pb superconductors and in situ shadowed junctions in a single-step molecular beam epitaxy process. We investigate correlations between fabrication parameters, junction morphologies, and electronic transport properties of the junctions and show that the examined in situ shadowed junctions are of significantly higher quality than the etched junctions. By varying the edge sharpness of the shadow junctions, we show that the sharpest edges yield the highest junction transparency for all three examined semiconductors. Further, critical supercurrent measurements reveal an extraordinarily high ICRN, close to the KO-2 limit. This study demonstrates a promising engineering path toward reliable gate-tunable superconducting qubits. ... Read more

ArenAPoort is an area in Amsterdam’s Zuidoost (Southeast) district, with multiple functions including working, shopping, and entertainment. Most importantly, it is an event area with three famous venues: Johan Cruijff ArenA, Ziggo Dome, and AFAS Live.
Hundreds of events are held in this area every year. During the event period, mobility can always draw a concern. The Operational Mobility Center (OMC) takes charge of the mobility flows, aiming at improving the mobility situation during events in the ArenAPoort. They are now collecting traffic data to help make predictions on traffic situations of future events and to reactively take precautions. This brings the consideration of whether there are other ways of using the data, for example, making use of data to intervene in visitors’ behavior.
In collaboration with the OMC, this master thesis aims to improve the mobility situation around the ArenAPoort during events by making use of data to change visitors’ mobility behavior. The final outcome is an application that can help visitors to plan their event experience in the ArenAPoort.
The project process follows the double-diamond model. It starts with an introduction of the project background, including the context, the organization OMC, and a project brief. After figuring out the background and having the project brief, four research questions are put forward, aiming to have a deeper understanding of the context, gain an empathy with the target group, and seek for theoretical support. Several research activities were taken, including desk research and field research.
According to research results, a design goal is formulated, together with design guidelines. Next, a series of co-creation sessions were performed for ideation. Based on the ideation results, 13 initial ideas are generated, and after two rounds of evaluation, ideas were summarized and integrated.
The next step is to conceptualize the ideas to a complete concept. During this process, the information structure and the user flow of the concept are defined, together with wireframes of key screens. Evaluation is conducted to assess the concept. Based on evaluation results, a final round of iteration was conducted, and the design is finalized.
Six end-users and two experts from the OMC took part in the evaluation of the final design. By summarizing and concluding evaluation results, overall conclusions of the project are drawn, together with the project limitation, future recommendation, and a personal reflection. ... Read more

III-V semiconductor nanowires have shown great potential in various quantum transport experiments. However, realizing a scalable high-quality nanowire-based platform that could lead to quantum information applications has been challenging. Here, we study the potential of selective area growth by molecular beam epitaxy of InAs nanowire networks grown on GaAs-based buffer layers, where Sb is used as a surfactant. The buffered geometry allows for substantial elastic strain relaxation and a strong enhancement of field effect mobility. We show that the networks possess strong spin-orbit interaction and long phase-coherence lengths with a temperature dependence indicating ballistic transport. With these findings, and the compatibility of the growth method with hybrid epitaxy, we conclude that the material platform fulfills the requirements for a wide range of quantum experiments and applications. ... Read more