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Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 58: Superconductivity: Qubits 2

TT 58.9: Talk

Thursday, April 4, 2019, 17:15–17:30, Theater

Phonon traps to reduce the quasiparticle density in superconducting circuits — •Francesco Valenti1,2, Fabio Henriques1, Maria Martinez3,4, Lukas Grünhaupt1, Daria Gusenkova1, Julian Ferrero1, Sebastian T. Skacel5, Nataliya Maleeva1, Alexey V. Ustinov1,6, and Ioan M. Pop1,51Physikalisches Institut, Karlsruhe Institue of Technology, 76131 Karlsruhe, Germany — 2Institute for Data Processing and Electronics, Karlsruhe Institue of Technology, 76344 Eggenstein-Leopoldshafen, Germany — 3Laboratorio de Física Nuclear y Astropartículas, Universidad de Zaragoza, C/ Pedro Cerbuna 12, 50009 Zaragoza, Spain — 4Fundacíon ARAID, Av. de Ranillas 1D, 50018 Zaragoza, Spain — 5Institute of Nanotechnology, Karlsruhe Institue of Technology, 76344 Eggenstein-Leopoldshafen, Germany — 6Russian Quantum Center, National University of Science and Technology MISIS, 119049 Moscow, Russia

Out of equilibrium quasiparticles (QPs) are a main source of dissipation and noise in superconducting circuits, and pinpointing their origin and decreasing their density remain outstanding tasks. The generation-recombination processes of QPs link their dynamics to the phonon dynamics of the circuit + substrate ensemble. We demonstrate that surrounding granular aluminum resonators with lower gapped aluminum islands increases the internal quality factors of the resonators in the single photon regime, suppresses the noise, and reduces the rate of observed QP generation events. The aluminum islands are positioned far enough from the resonators to be electromagnetically decoupled, and we attribute the decrease in dissipation and noise to phonon trapping.

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