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Advertising division: PGI-9 - Semiconductor Nanoelectronics
Reference number: D151/2018, Physics, Nanoengineering;

Master thesis: Hybridization of adjacent Majorana modes

Start of work: by arrangement

Background:
We are in the midst of the second quantum revolution. Research institutes and companies worldwide work towards harnessing the power of quantum physics for technological applications. Quantum computation in particular promises to solve problems, which the most powerful supercomputers cannot. Topological quantum computation has been predicted to have an intrinsic protection against quantum errors [1]. A fully degenerated subspace of quantum states make relaxation (and decoherence) in these kinds of Quantum bits (Qubits) impossible, though other (more unlikely) errors can occur (e.g. quasi particle poisoning). In total this promises to reduce the required overhead of physical Qubits per logical Qubit from 1,000-10,000 (estimated for Qubits without topological protection) to only 10. Once demonstrated, topological quantum processors could become the most promising computational platform in terms of scalability. For building a first successful prototype, topological materials need being integrated into superconducting circuitry.

Your task:
In Jülich we focus on topological insulators of the Bi2-xSbxTe3 family, because those materials provide an exemplarily large topological gap, which is necessary for the intrinsic protection of the quantum states. For creating Majorana modes in these materials, superconducting electrodes have to be deposited on top of the surface of our topological materials. Importantly the interface between superconductor and topological insulator must be of superior quality. In the research center of Jülich we developed a novel fabrication technique, which allows for fabrication of high-quality superconductor (S) – topological insulator (TI) hybrid devices under ultra-high vacuum conditions (details about the fabrication process can be found here: [2]); The process provides highly transparent S-TI interfaces and transport experiments in as-prepared Josephson junctions indicate the presence of Majorana bound states. In a next step Majorana zero modes and their hybridization as function of distance to each other are investigated [3]. Therefore you will fabricate complex arrays of superconductor – topological insulator networks fully in-situ. The responsible Ph.D student will teach and guide you through each fabrication step of this highly complex and novel process. As-prepared arrays are transported to Shanghai for low temperature scanning tunnel spectroscopy [4].

References:
[1]: https://www.youtube.com/watch?v=qj-w6ISQL5Y
[2]: https://arxiv.org/abs/1711.01665
[3]: https://arxiv.org/abs/1603.03217
[4]: https://arxiv.org/abs/1603.02549

Techniques to be used:
Molecular beam epitaxy, nanofabrication (electron beam lithography, reactive ion etching etc.), scanning tunneling microscopy at cryogenic temperatures.

Requirements:
University studies in physics or nanoengineering; interested in new physics and phenomena; ability to work in a team and autonomously.

We offer:

  • A pleasant working environment within a highly competent, international team in one of the most prestigious research facilities in Europe
  • You will be supported by top-end scientific and technical infrastructure as well as close guidance by experts
  • You will have the opportunity to work with excited researchers from various scientific fields and take part in the fabrication and characterization of cutting edge topological devices
  • The master thesis is remunerated

Contact:
Dr. Peter Schüffelgen
Peter Grünberg Institute (PGI)
PGI-9: Topological quantum computation
52425 Jülich

E-Mail: p.schueffelgen@fz-juelich.de
http://www.fz-juelich.de/pgi/pgi-9/EN