Hybridized-Mode Parametric Amplifier in Kinetic-Inductance Circuits

TL;DR

This paper introduces a high-gain, broadband parametric amplifier using coupled kinetic-inductance resonators made from NbTiN and NbN, offering advantages over traditional Josephson-based amplifiers in power handling and magnetic resilience.

Contribution

It demonstrates a novel two-mode kinetic-inductance parametric amplifier with high gain, bandwidth, and power handling, using distributed Kerr nonlinearity in NbTiN and NbN materials.

Findings

Achieved gains approaching 40 dB and gain-bandwidth products up to 6.9 MHz.

Demonstrated 1-dB compression powers 100-1000 times higher than Josephson amplifiers.

Validated a coupled-mode theoretical model matching experimental results.

Abstract

Parametric amplification is essential for quantum measurement, enabling the amplification of weak microwave signals with minimal added noise. While Josephson-junction-based amplifiers have become standard in superconducting quantum circuits, their magnetic sensitivity, limited saturation power, and sub-kelvin operating requirements motivate the development of alternative nonlinear platforms. Here we demonstrate a two-mode kinetic-inductance parametric amplifier based on a pair of capacitively coupled Kerr-nonlinear resonators fabricated from NbTiN and NbN thin films. The distributed Kerr nonlinearity of these materials enables nondegenerate four-wave-mixing amplification with gains approaching 40 dB, gain-bandwidth products up to 6.9 MHz, and 1-dB compression powers two to three orders of magnitude higher than those of state-of-the-art Josephson amplifiers. A coupled-mode theoretical model accurately captures the pump-induced modification of the hybridized modes and quantitatively reproduces the observed signal and idler responses. The NbN device exhibits a significantly larger Kerr coefficient and superior gain-bandwidth performance, highlighting the advantages of high-kinetic-inductance materials. Our results establish coupled kinetic-inductance resonators as a robust platform for broadband, high-power, and magnetically resilient quantum-limited amplification, offering a scalable route for advanced readout in superconducting qubits, spin ensembles, quantum dots, and other microwave-quantum technologies.