Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Qubits 1

TT 40.8: Vortrag

Mittwoch, 3. April 2019, 11:30–11:45, H48

Coherence of a granular aluminum fluxonium qubit — •Martin Spiecker, Lukas Grünhaupt, Daria Gusenkova, Nataliya Maleeva, Sebastian T. Skacel, Ivan Takmakov, Francesco Valenti, Patrick Winkel, Hannes Rotzinger, Alexey V. Ustinov, and Ioan M. Pop — Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

A promising alternative for the implementation of superinductors, compared to the predominantly used mesoscopic Josephson junction arrays, is granular aluminum (grAl), with a microstructure consisting of pure aluminum grains embedded in an AlOx matrix, effectively forming a self-assembled Josephson junction network [1]. This material offers a large kinetic inductance, while its non-linearity is orders of magnitude smaller than that of Josephson junction arrays [2]. We present a fluxonium qubit employing a granular aluminium superinductor with coherence times T up to 23 µs and T up to 30 µs at the flux bias sweet spot. The measured T approaches the limit 2 * T [3]. These coherence times recommend granular aluminum for increasingly complex protected superconducting quantum circuits, while they also evidence the need to further investigate and mitigate loss mechanisms in high impedance circuits.
Grünhaupt et al., Phys. Rev. Lett. 121, 117001 (2018)
Maleeva et al., Nat. Commun. 9, 3889 (2018)
Grünhaupt and Spiecker et al., arXiv:1809.10646 (2018)