Parametric Amplification via Superconducting Contacts in a Ka Band Niobium Pillbox Cavity

Abstract

Superconducting parametric amplifiers are commonly fabricated using planar transmission lines with a nonlinear inductance provided by either Josephson junctions or the intrinsic kinetic inductance of the thin film. However, Banys et al. (J Low Temp Phys, 2020) reported nonlinear behaviour in a niobium pillbox cavity, hypothesising that below T_c, the pair iris-bulk resonator would act as a superconducting contact surface exploiting a Josephson-like nonlinearity. This work investigates this effect further by applying Keysight Technologies’ Advanced Design System (ADS) to simulate the cavity using an equivalent circuit model that includes a user defined Josephson inductance component. The simulations show that for a resonance centred at nu _0=30.649 GHz, when two tones (pump and signal) are injected into the cavity, mixing and parametric gain occur. The maximum achievable gain is explored when the resonator is taken to its bifurcation energy. These results are compared to cryogenic measurements where the pump and the signal are provided by a Vector Network Analyzer.