Strong kinetic-inductance Kerr nonlinearity with titanium nitride nanowires

TL;DR

This paper demonstrates enhanced kinetic-inductance Kerr nonlinearity in titanium nitride nanowires, enabling high-frequency quantum devices with significant nonlinearity at elevated temperatures.

Contribution

It introduces a method to magnify KI nonlinearity by confining current density in TiN nanowires, achieving large Kerr shifts suitable for quantum applications.

Findings

Maximum Kerr-shift per photon of 123.5 kHz

Nonlinearity-to-linewidth ratio of 21%

Potential to reach strong quantum nonlinearity regime

Abstract

Thin films of disordered superconductors such as titanium nitride (TiN) exhibit large kinetic inductance (KI), high critical temperature, and large quality factors at the single-photon level. KI nonlinearity can be exploited as an alternative to Josephson junctions for creating novel nonlinear quantum devices with the potential to operate at higher frequencies and at elevated temperatures. We study a means of magnifying KI nonlinearity by confining the current density of resonant electromagnetic modes in nanowires with a small volume $V \simeq 10^{-4}\text{um}^3$. Using this concept, we realize microwave-frequency Kerr cavities with a maximum Kerr-shift per photon of $K/2\pi = 123.5 \pm 3$ kHz and report a nonlinearity-to-linewidth ratio $K/\gamma = 21\%$. With improved design, our devices are expected to approach the regime of strong quantum nonlinearity in the millimeter-wave spectrum.