Superconducting parametric amplifiers (SPAs) have seen great interest in recent years due to their high gain and quantum limited noise performance. Among these amplifiers, resonant SPAs have been widely developed for experiments where ultralow-noise narrow-band amplification is of interest, such as the search for axion dark matter in particle physics and the detection of spectroscopic lines in astrophysics, while also finding applications in quantum computing. This work presents an amplifier based on a complementary split-ring resonator, patterned on a Nb Ti -coated sapphire substrate embedded within a waveguide, designed to work at a set of four narrow frequency bands throughout the K band (18–27 GHz) using the kinetic inductance of the superconducting film. The S -parameters measured at 400 mK, using a sorption cooler, show the four resonances between 23.3 and 26.3 GHz at 1-GHz spacing, with a maximum transmission on resonance of − 1 dB. Four-wave mixing has been observed with each resonance, and a maximum signal gain of 30 dB has been measured, corresponding to 29 dB of insertion gain. The noise performance of the amplifier has been measured, showing an added noise of 1.2 half-quanta at 400 mK. These results are relevant to high-frequency axion dark matter experiments and help motivate the exploration of higher frequencies in quantum technologies.
Superconducting parametric amplifier, originally developed more than half a century ago, gained renewed interests in some experiments of superconducting quantum electronics about a decade ago, and now has become an indispensable tool in the field of superconducting quantum information processing. More recently, there are several proposals, where a parametric oscillator, which is a parametric amplifier pumped above the threshold, is used as a quantum bit and the network of the parametric oscillators solve some computational tasks. Here, we briefly introduce the research activity on the development of the superconducting parametric devices, including our results, with some historical backgrounds.
At microwave frequencies, Josephson junction arrays have been widely employed to create metamaterials exhibiting a third-order (
χ(3)) nonlinearity, analogous to the Kerr effect in optics. These nonlinear metamaterials enable parametric amplification, as in Josephson Travelling-Wave Parametric Amplifiers (JTWPAs), which achieve quantum-limited noise performance over multi-gigahertz bandwidths. The exceptional properties of JTWPAs make them ideal for the sensitive readout of weak microwave signals, with applications in quantum computing, astrophysics, and fundamental physics experiments. Extending JTWPAs to higher frequencies, such as the W-band (70–110 GHz), holds promise for first-stage amplification in astronomical receivers, lowering system noise; as well as for reading out emerging superconducting qubit architectures at these frequencies. In this work, we investigate the
χ(3)nonlinear properties of Josephson arrays operating in the W-band as a step toward realising parametric gain at these frequencies. We designed and fabricated an array composed of 704 Nb/Al-AlO
x/Nb tunnel junctions and experimentally demonstrated four-wave mixing via idler tone generation, providing clear evidence of third-order nonlinearity. These results mark an important step toward novel millimetre-wave and sub-millimetre-wave parametric-amplifier-based receiver technologies.