Parametric amplification via superconducting contacts in a Ka band niobium pillbox cavity

TL;DR

This paper explores superconducting parametric amplification in a niobium pillbox cavity at Ka band frequencies, demonstrating mixing and gain via a Josephson-like non-linearity through simulations and cryogenic measurements.

Contribution

It introduces a novel approach using superconducting contacts in a niobium cavity to achieve parametric amplification at microwave frequencies.

Findings

Parametric gain observed at 30.649 GHz

Simulations align with cryogenic measurement results

Maximum gain near bifurcation energy

Abstract

Superconducting parametric amplifiers are commonly fabricated using planar transmission lines with a non-linear inductance provided by either Josephson junctions or the intrinsic kinetic inductance of the thin film. However, Banys et al. [1] reported non-linear behaviour in a niobium pillbox cavity, hypothesising that below Tc, the pair iris-bulk resonator would act as a superconducting contact surface exploiting a Josephson-like non-linearity. 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 nu0 = 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 signal are provided by a Vector Network Analyzer.