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Phonon traps reduce the quasiparticle density in superconducting circuits

Henriques, Fabio; Valenti, Francesco; Charpentier, Thibault; Lagoin, Marc; Gouriou, Clement; Martínez, M.; Cardani, L.; Vignati, M.; Grünhaupt, Lukas; Gusenkova, Daria; Ferrero, Julian; Skacel, Sebastian T.; Wernsdorfer, Wolfgang; Ustinov, Alexey V.; Catelani, G.; Sander, Oliver; Pop, Ioan M.

Abstract:
Out of equilibrium quasiparticles (QPs) are one of the main sources of decoherence in superconducting quantum circuits, and are particularly detrimental in devices with high kinetic inductance, such as high impedance resonators, qubits, and detectors. Despite significant progress in the understanding of QP dynamics, pinpointing their origin and decreasing their density remain outstanding tasks. The cyclic process of recombination and generation of QPs implies the exchange of phonons between the superconducting thin film and the underlying substrate. Reducing the number of substrate phonons with frequencies exceeding the spectral gap of the superconductor should result in a reduction of QPs. Indeed, we demonstrate that surrounding high impedance resonators made of granular aluminum (grAl) with lower gapped thin film 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 bursts. The aluminum islands are positioned far enough from the resonators to be electromagnetically decoupled, thus not changing the resonator frequency, nor the loading. ... mehr



Zugehörige Institution(en) am KIT Institut für Nanotechnologie (INT)
Institut für Prozessdatenverarbeitung und Elektronik (IPE)
Physikalisches Institut (PHI)
Publikationstyp Forschungsbericht/Preprint
Publikationsjahr 2019
Sprache Englisch
Identifikator ISSN: 0003-6951, 1077-3118, 1520-8842
KITopen-ID: 1000104832
HGF-Programm 43.21.02 (POF III, LK 01) Quantum Properties of Nanostructures
Verlag American Institute of Physics (AIP)
Nachgewiesen in arXiv
Relationen in KITopen
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