Quantum Nanoelectronics Seminar : Thomas Schäpers

Tuesday 27 February 2018 - 14h00 - Room « Remy Lemaire » (K223)

Nanowire-based structures for applications in quantum information processing
Thomas Schäpers (Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Germany)

Nanowires are not only interesting as building blocks for future nanoelectronic device applications they are also very promising candidates for realizing circuits for quantum information processing. Here, two major directions can be identified. First, nanowires can be employed to create Majorana fermions for robust topological quantum computing. One essential prerequisite is the verification of spin helical transport. In quantum point contacts based on InAs nanowires we achieved ballistic transport with quantized conductance. At the last step a dip feature is observed which is attributed to the presence of helical states [1]. The emergence of this dip feature is explained in the framework of exchange interactions. Recently, our research towards topological quantum computation is extended by using nanowires based on topological insulators such as Bi2Te3 or Sb2Te3. As a second option for applications in quantum information, semiconductor nanowires are also interesting for gate-controlled Josephson junctions in transmon qubits. In order to optimize the junction performance, the InAs nanowire is covered in-situ by a superconducting Al or Nb shell. These junctions are subsequently integrated in a superconducting resonator circuit.
Work done in collaboration with: D. Grützmacher, Y. Günel, N. Güsken, A. R. Jalil, J. Kölzer, S. Heedt, M. Lepsa, G. Mussler, T. Rieger, D. Rosenbach, J. Schubert, P. Schüffelgen, S. Trellenkamp, Ch. Weyrich, P. Zellekens (Jülich), N. Traverso Ziani, F. Crepin, B. Trauzettel (University of Würzburg), F. W. Prost (University Duisburg-Essen), M. Weides, S. Schlör (KIT Karlsruhe).

[1] S. Heedt, N. T. Ziani, F. Crepin, W. Prost, S. Trellenkamp, J. Schubert, D. Grützmacher, B. Trauzettel, Th. Schäpers, Nature Physics, 13, 563 (2017). doi:10.1038/nphys4070

Contact : Thomas Schäpers

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Seminar Josep Puigmartí-Luis

Wednesday 28 February 2018 - 10h30 - Grenoble INP - Phelma

Engineering liquid-liquid interfacial reactions for materials synthesis

Dr. Josep Puigmartí-Luis
ETH Zürich
Department of Chemistry and Applied Biosciences
Institute for Chemical and Bioengineering

If you want to speak to Dr. Josep Puigmartí-Luis after the seminar, please contact :
David Munoz-Rojas :

Self-assembly has long being used to control materials synthesis and their function. The main reason being that, like in nature, a full control over self-assembly processes could lead to functional materials with rationalized structure-property correlations, a long-time sought in materials engineering.
In this seminar, Dr. Josep Puigmarti-Luis will show that controlled heat and mass transport processes accomplished in microfluidic devices (a top-down approach) are excellent physicochemical vehicles to control the synthesis and rational design of functional matter in time and space (a bottom-up approach).

Dr. Josep Puigmarti-Luis is a senior scientist and group leader in Prof. Andrew deMello’s group at ETH Zurich, where he leads a number of projects, e.g. an ERC Starting Grant (2016-2021) a Swiss National Project (2015-2019) and an ETH Grant (2018-2021). Dr. Puigmartí-Luis is a scientist who completed a master in chemical engineering at “Institut Químico de Serrià (IQS)” (2003) and did a PhD in material sciences at Institut de Ciència de Materials de Barcelona (ICMAB). His work in supramolecular and flow chemistry, has been awarded with “Premi Antoni de Martí i Franquès de Ciències Químiques”, award from the Institut d’Estudis Catalans (2009), St. Jordi award from the Institut d’Estudis Catalans and the Societat Catalana de Química (2006) and an ETH fellowship award in 2008. In 2012, he was also appointed a Ramon Y Cajal researcher. Since 2014, he relocated his research activities in Switzerland.

Quantum Nanoelectronics Seminar : Erik Bakkers

Tuesday 6 March 2018 - 14h00 - Room « Remy Lemaire » (K223)

Bottom-up grown nanowire quantum devices
Erik Bakkers (Technische Universiteit Eindhoven)

InSb nanowires are used to detect first signatures of quasi particles called Majorana fermions. Recently, different schemes for performing braiding operations and uncovering the non-Abelian statistics of Majorana fermions are proposed. Such operations are fundamental for topological quantum computing. For such a universal computational architecture the realization of a near-perfect nanowire network assembly is needed in which Majorana states are coherently coupled.
Here, we demonstrate a generic process by which we can design any proposed braiding device by manipulating an InP substrate and thereby the nanowire growth position and orientation [1]. This approach combines recent advances in materials growth and theoretical proposals. Our method leads to highly controlled growth of InSb nanowire networks with single crystalline wire-wire junctions. Additionally, nanowire “hashtag” structures are grown with a high yield and contacted. In these devices, the Aharonov–Bohm (AB) effect is observed, demonstrating phase coherent transport. These measurements reveal the high quality of these structures. This generic platform will open new applications in quantum information processing. Furthermore, these structures are well suited for epitaxial shadow growth of a superconductor on the nanowire facets. We study the growth of superconductors on nanowires and reveal the electronic properties.

1. S. Gazibegovic et al. Nature 548 (2017), 434

Contact : Erik Bakkers

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Quantum Nanoelectronics Seminar : Ines Safi

Tuesday 13 March 2018 - 14h00 - Room « Remy Lemaire » (K223)

Ines Safi (Laboratoire de Physique des Solides, Orsay)

Contact : Ines Safi

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