We have generated frequency combs spanning 0.5 to 20 GHz in superconducting half wave resonators at T=3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high cr
itical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory and the measured spectrum is shown to agree with the theory. The sideband spacing is measured to be accurate to 1 part in 10 million. The sidebands coalesce into a continuous comb structure that has been observed to cover at least 6 octaves in frequency.
We present the characteristics of superconducting nanowire single photon detectors (SNSPDs) fabricated from amorphous Mo0.75Ge0.25 thin-films. Fabricated devices show a saturation of the internal detection efficiency at temperatures below 1 K, with s
ystem dark count rates below 500 counts per second. Operation in a Gifford-McMahon (GM) cryocooler at 2.5 K is possible with system detection efficiencies (SDE) exceeding 20% for SNSPDs which have not been optimized for high detection efficiency.
We demonstrate enhanced relaxation and dephasing times of transmon qubits, up to ~ 60 mu s by fabricating the interdigitated shunting capacitors using titanium nitride (TiN). Compared to lift-off aluminum deposited simultaneously with the Josephson j
unction, this represents as much as a six-fold improvement and provides evidence that previous planar transmon coherence times are limited by surface losses from two-level system (TLS) defects residing at or near interfaces. Concurrently, we observe an anomalous temperature dependent frequency shift of TiN resonators which is inconsistent with the predicted TLS model.
