Frequency-tunable Kerr-free three-wave mixing with a gradiometric SNAIL

TL;DR

This paper introduces a gradiometric SNAIL device that allows independent tuning of inductance and Kerr effect, enabling flexible three-wave mixing with suppressed parasitic effects over a broad frequency range.

Contribution

It presents a novel doubly-flux biased SNAIL that overcomes the limitation of single Kerr-free points, allowing continuous Kerr suppression for improved quantum amplification.

Findings

Suppression of Kerr effect over a 1.7 GHz frequency range.

Independent tuning of inductance and Kerr coefficient.

Demonstration of enhanced three-wave mixing performance.

Abstract

Three-wave mixing is a key process in superconducting quantum information processing, being involved in quantum-limited amplification and parametric coupling between superconducting cavities. These operations can be implemented by SNAIL-based devices that present a Kerr-free flux-bias point where unwanted parasitic effects such as Stark shift are suppressed. However, with a single flux-bias parameter, these circuits can only host one Kerr-free point, limiting the range of their applications. In this Letter, we demonstrate how to overcome this constraint with a gradiometric SNAIL, a doubly-flux biased superconducting circuit for which both effective inductance and Kerr coefficient can be independently tuned. Experimental data show the capability of the gradiometric SNAIL to suppress Kerr effect in a three-wave mixing parametric amplifier over a continuum of flux bias points corresponding to a 1.7 GHz range of operating frequencies.