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Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 64: Poster: Topology

FM 64.3: Poster

Wednesday, September 25, 2019, 16:30–18:30, Tents

Designing transmon qubits to study topological insulator Josephson junctions in a 3D cavity — •Jonas Krause1,2, Christian Dickel1, Junya Feng1, Richard Bounds1, Shabir Barzanjeh3, Johannes Fink3, and Yoichi Ando11University of Cologne — 2ETH Zurich — 3IST Austria

Transmon qubits are a leading platform for quantum computing and have also been used to study unconventional Josephson junctions based on proximitized semiconductor nanowires, graphene and carbon nanotubes. We aim to use a transmon to study topological insulator (TI) Josephson junctions. TI-superconductor hybrid devices are predicted to host Majorana bound states that can be used for topological quantum computing. The transmon has in this context been proposed as a readout circuit via charge-parity detection. However, many proposals require considerable magnetic fields. Copper cavities are unaffected by strong magnetic fields and provide a clean microwave environment, making them ideal for the study of the transmon response to magnetic fields. We first study the magnetic-field dependence in conventional aluminum transmons and then move to TI devices. The transmon design for this purpose leads to a few changes from conventional 3D-cavity transmons: Higher charging energies are likely desirable for investigating quasiparticle poisoning dynamics. We will also investigate the effect of vortex traps on coherence and field resilience of the transmons. As opposed to on-chip resonators, the 3D setup requires minimal fabrication steps, thus implementing a fast and easy-to-use microwave probe station for TI junctions.

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