%0 Journal Article
%A Grünhaupt, Lukas
%A Maleeva, Nataliya
%A Skacel, Sebastian T.
%A Calvo, Martino
%A Levy-Bertrand, Florence
%A Ustinov, Alexey V.
%A Rotzinger, Hannes
%A Monfardini, Alessandro
%A Catelani, Gianluigi
%A Pop, Ioan M.
%T Loss Mechanisms and Quasiparticle Dynamics in Superconducting Microwave Resonators Made of Thin-Film Granular Aluminum
%J Physical review letters
%V 121
%N 11
%@ 1079-7114
%C College Park, Md.
%I APS
%M FZJ-2018-05287
%P 117001
%D 2018
%X Superconducting high kinetic inductance elements constitute a valuable resource for quantum circuit design and millimeter-wave detection. Granular aluminum (grAl) in the superconducting regime 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/AlOx/Al Josephson junction fabrication. We characterize microwave resonators fabricated from grAl with a room temperature resistivity of 4×103  μΩ cm, which is a factor of 3 below the superconductor to insulator transition, showing a kinetic inductance fraction close to unity. The measured internal quality factors are on the order of Qi=105 in the single photon regime, and we demonstrate that nonequilibrium quasiparticles (QPs) constitute the dominant loss mechanism. We extract QP relaxation times in the range of 1 s and we observe QP bursts every ∼20  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 nonequilibrium QPs.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:30265102
%U <Go to ISI:>//WOS:000444586600016
%R 10.1103/PhysRevLett.121.117001
%U https://juser.fz-juelich.de/record/851772