https://doi.org/10.1140/epjqt/s40507-025-00367-w
Research
Intrinsic quality factors approaching 10 million in superconducting planar resonators enabled by spiral geometry
1
RIKEN Center for Quantum Computing, 351-0198, Wako, Saitama, Japan
2
Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, 153-8902, Tokyo, Japan
3
Advanced ICT Research Institute, National Institute of Information and Communications Technology (NICT), 651-2492, Kobe, Hyogo, Japan
4
Inamori Research Institute for Science (InaRIS), 600-8411, Kyoto-shi, Kyoto, Japan
a
yusuke.tominaga@riken.jp
b
u-atsushi@g.ecc.u-tokyo.ac.jp
Received:
27
February
2025
Accepted:
16
May
2025
Published online:
13
June
2025
This study investigates the use of spiral geometry in superconducting resonators to achieve high intrinsic quality factors, crucial for applications in quantum computation and quantum sensing. We fabricated Archimedean Spiral Resonators (ASRs) using domain-matched epitaxially grown titanium nitride (TiN) on silicon wafers, achieving intrinsic quality factors of 
at the single-photon level and 
at high power, which is more than twice as high as those for coplanar waveguide (CPW) resonators under identical conditions on the same chip. We conducted a comprehensive numerical analysis using COMSOL to calculate surface participation ratios (PRs) at critical interfaces: metal-air, metal-substrate, and substrate-air. Our findings reveal that ASRs have lower PRs than CPWs, explaining their superior quality factors and reduced coupling to two-level systems (TLSs).
Key words: Superconducting resonators / Two-level systems / Surface participation ratio
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjqt/s40507-025-00367-w.
© The Author(s) 2025
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