Quasiparticle-tuned superconducting mixer

We have successfully employed the recently observed quasiparticle admittance of a superconducting tunnel junction as the tuning element for a superconductor- insulator-superconductor mixer. This is the first demonstration of an electronic on-chip tuning element for a superconducting detector. We observe an increase in the dynamic resistance and an improvement in mixer gain and noise temperature as the dc bias voltage of the tuning junction array is varied. We compare our results with the quantum theory of mixing.