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@ARTICLE{Henriques:866713,
      author       = {Henriques, Fabio and Valenti, Francesco and Charpentier,
                      Thibault and Lagoin, Marc and Gouriou, Clement and
                      Martínez, Maria and Cardani, Laura and Vignati, Marco and
                      Grünhaupt, Lukas and Gusenkova, Daria and Ferrero, Julian
                      and Skacel, Sebastian T. and Wernsdorfer, Wolfgang and
                      Ustinov, Alexey V. and Catelani, Gianluigi and Sander,
                      Oliver and Pop, Ioan M.},
      title        = {{P}honon traps reduce the quasiparticle density in
                      superconducting circuits},
      journal      = {Applied physics letters},
      volume       = {115},
      number       = {21},
      issn         = {1077-3118},
      address      = {Melville, NY},
      publisher    = {American Inst. of Physics},
      reportid     = {FZJ-2019-05783},
      pages        = {212601 -},
      year         = {2019},
      abstract     = {Out of equilibrium quasiparticles (QPs) are one of the main
                      sources of decoherence in superconducting quantum circuits
                      and one that is 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. We therefore attribute the improvements observed in
                      grAl resonators to phonon trapping at frequencies close to
                      the spectral gap of aluminum, well below the grAl gap.},
      cin          = {PGI-11},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-11-20170113},
      pnm          = {144 - Controlling Collective States (POF3-144)},
      pid          = {G:(DE-HGF)POF3-144},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000504303900018},
      doi          = {10.1063/1.5124967},
      url          = {https://juser.fz-juelich.de/record/866713},
}