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TT: Fachverband Tiefe Temperaturen

TT 49: Poster Session: Superconductivity

TT 49.39: Poster

Mittwoch, 3. April 2019, 15:00–18:30, Poster D

Design of a granular aluminium fluxonium qubit with phonon traps — •Alexandru Ionita¹, Martin Spiecker¹, Lukas Grünhaupt¹, Daria Gusenkova¹, and Ioan Pop^{1, 2} — ¹Physikalisches Institut, Karlsruhe Institute of Technology, Germany — ²Institute of Nanotechnology, Karlsruhe Institute of Technology, Germany

Fluxonium qubits employing the high kinetic inductance of granular aluminum (grAl) have recently been implemented, demonstrating state of the art coherence. One of the main sources of decoherence can be attributed to non-equilibrium quasiparticles (QPs) inside the grAl superinductance of the qubit. The generation of QPs can be partially traced back to bursts of phonons in the sapphire substrate, of yet unknown origin, which are followed by a slow QP population decay on a characteristic time-scale of 1 second. We present a grAl fluxonium design in a 2D-environment with phonon traps filling the entire waver, potentially decreasing the number of quasiparticle bursts.