[18p-B5-1~15] 11.4 アナログ応用および関連技術

16:15 〜 16:30英語発表

[18p-B5-12] Two-level System Loss of SiO₂ Measured at 4 K with Millimeter Superconducting Thin-film Resonators

〇Wenlei Shan¹, Shohei Ezaki¹ (1.NAOJ)

キーワード：

Two-Level System、Transmission Loss

Two-level system (TLS) loss inherited in amorphous dielectric materials have been intensively investigated at millikelvin temperatures for its importance in limiting the performance of superconducting qubit devices and incoherent detectors based on superconducting resonators. In contrast, the experimental evidence of TLS loss in superconducting transmission lines at liquid helium temperatures and its relative significance with respect to other losses are not fully revealed. We investigated the loss of amorphous SiO₂ at liquid helium temperatures in a frequency range of 130-170 GHz by measuring Q factors of niobium microstrip and coplanar waveguide resonators. The measured losses show remarkable power and frequency-dependence, which is consistent with that modeled by TLS with a weak-field loss of about 3-7x10^-3 depending on fabrication methods. The TLS loss and the quasiparticle loss exchanges the leading role at about 4 K in the measured frequency range, and this relationship is expected to hold in sub-millimeter wavelengths as well.