SQUIDs as tunable inductors integrated in the design of filters

Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2007

This work presents the dc-SQUID based tunable inductance and its relevance into the design of resonators and filters for the qubit application. The SQUID inductance depends on loop inductance, applied magnetic field and bias current for a given thermal noise. Tunable resonators and filters have been designed by replacing the inductances of the resonator with a chain of SQUIDs in series. A narrow bandpass filter with variable central frequency is useful for superconducting qubit applications, specifically for improving the line widths of Josephson junction oscillators. We have designed a tunable 3.5 GHz resonator and 2 GHz 7 stage Chebyshev filters to be fabricated in Hypres 4.5 kA/cm2 process. According to simulations, up to 50% of the operating frequency of the designed filter can be varied. We present data that shows a frequency tuning of >2 GHz.