Frequency Control of Superconducting Resonators Using Integrated Interferometers
Year: 2026
Type: other
Abstract: Predictable frequency trimming of superconducting resonators at liquid-helium temperatures re-quires a tuning element whose usable range remains well defined despite screening currents andhysteresis. Here we realize flux-controlled λ/4 coplanar-waveguide resonators terminated by two-junction DC SQUIDs fabricated in a standard Nb/Al-AlOx/Nb multilayer process. Integratedon-chip flux-bias lines allow the resonant frequency to be controlled at 4.2 K. RF measurementsshow periodic frequency modulation with applied flux, with a maximum shift of δfr = 8.63 MHzand a single-valued tuning interval of δfr0 = 2.85 MHz. Near half-integer flux quanta, the responseexhibits hysteretic jumps caused by the finite SQUID loop inductance, so that the usable single-valued tuning interval is smaller than the full modulation range. We develop a semi-analyticalmodel of the frequency-flux response, supported by numerical simulations and 3D electromagneticextraction of the device parameters, which reproduces the measured hysteretic branches and iden-tifies the SQUID loop inductance and junction critical current as the main parameters limiting theusable tuning range. These results provide a quantitative design framework for MHz-scale frequencytrimming of Nb superconducting resonators in 4 K cryogenic readout circuits
Source: AIP Publishing
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204137277