Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 79: Superconductivity: Superconducting Electronics - Circuit QED

TT 79.2: Talk

Thursday, March 15, 2018, 09:45–10:00, H 2053

Quasiparticle dynamics in microwave resonators from granular aluminum close to the superconductor to insulator transition — •Lukas Grünhaupt¹, Nataliya Maleeva¹, Sebastian T. Skacel¹, Florence Lévy-Bertrand², Alexey V. Ustinov^{1, 3}, Hannes Rotzinger¹, Alessandro Monfardini², and Ioan M. Pop¹ — ¹Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany — ²Institut Néel, CNRS and Université Grenoble Alpes, Grenoble, France — ³Russian Quantum Center, National University of Science and Technology MISIS, Moscow, Russia

Superconducting high kinetic inductance elements constitute a valuable resource for quantum circuit design and millimeter-wave detection. Granular aluminum (GrAl) is a particularly interesting material since it has already shown a kinetic inductance in the range of nH/ and its deposition is compatible with conventional Al/AlO_x/Al Josephson junction fabrication. We characterize microstrip resonators in the GHz range fabricated from GrAl thin films with resistivity and geometry dependent kinetic inductances between 0.3 and 2.0 nH/. Our results suggest that non-equilibrium quasiparticles limit their internal qualitiy factors at a level of 10⁵. We extract quasiparticle relaxation times on the order of 1 s and we observe quasiparticle producing events approximately every 30 s. The current level of coherence of GrAl resonators makes them attractive for integration in quantum devices, while it also evidences the need to reduce the density of non-equilibrium quasiparticles.