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 Valenti^1,2, Fabio Henriques¹, Maria Martinez^3,4, Lukas Grünhaupt¹, Daria Gusenkova¹, Julian Ferrero¹, Sebastian T. Skacel⁵, Nataliya Maleeva¹, Alexey V. Ustinov^1,6, and Ioan M. Pop^1,5 — ¹Physikalisches 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.