Centrala begrepp
A simple and versatile low-characteristic-impedance lumped-element resonator design based on a superconducting coplanar waveguide strip shunted with a parallel-plate capacitor, enabling tailored impedance and frequency in the sub-gigahertz regime while maintaining a small footprint.
Sammanfattning
The authors demonstrate a novel superconducting resonator design, dubbed the "tadpole resonator", which combines a short strip of a coplanar waveguide transmission line shorted at one end and shunted with a large parallel-plate capacitor at the other end. This design allows for tuning the characteristic impedance of the resonator to values as low as 2 Ω, while operating in the frequency range of 290 MHz to 1.1 GHz.
Key highlights:
The tadpole resonator design enables a wide range of characteristic impedances (2-10 Ω) and frequencies (290 MHz to 1.1 GHz) in a compact on-chip footprint.
The authors fabricated and characterized 12 tadpole resonators, reaching internal quality factors up to 8,500, corresponding to a dielectric loss tangent of 1.2 × 10−4 for the aluminum oxide used as the parallel-plate capacitor dielectric.
The resonator frequency can be accurately modeled using a simple lumped-element circuit approach, with the parallel-plate capacitance being the key tuning parameter.
The low characteristic impedance and concentrated magnetic field of the tadpole resonator make it a promising candidate for applications requiring strong inductive coupling, such as SQUID-mediated coupling schemes.
While the quality factors are moderate compared to high-frequency CPW resonators, the tadpole design offers advantages in terms of versatility, small footprint, and suitability for low-frequency applications.
Statistik
We demonstrate characteristic impedances ranging from Zc = 2 Ω to 10 Ω and a frequency range from f0 = 290 MHz to 1.1 GHz while reaching internal quality factors of order Qint = 8.5 × 103 translating into a loss tangent of tan(δ) = 1.2 × 10−4 for the aluminium oxide used as the dielectric in the parallel plate capacitor.
Citat
"The low characteristic impedance of the tadpole resonator renders it a promising candidate for achieving strong inductive coupling to other microwave components."
"We find an average internal quality factor of 5.2×103 at the intermediate probe power of −116 dBm."
"The internal quality factor increases linearly with probe power in the intermediate power range and displays saturation at both, low and high power limits."