Enhancing Intrinsic Quality Factors Approaching 10 Million in Superconducting Planar Resonators via Spiral Geometry

TL;DR

This paper demonstrates that spiral geometry superconducting resonators significantly improve intrinsic quality factors, reaching nearly 10 million, by reducing surface participation ratios and TLS interactions, outperforming traditional designs.

Contribution

It introduces spiral geometry resonators fabricated with TiN on silicon, achieving record-high quality factors and providing a detailed numerical analysis of surface participation ratios.

Findings

Achieved intrinsic Q-factors of nearly 10 million at single-photon levels.

Spiral resonators have lower surface participation ratios than coplanar waveguides.

Numerical analysis explains the superior performance due to reduced TLS coupling.

Abstract

This study investigates the use of spiral geometry in superconducting resonators to achieve high intrinsic quality factors, crucial for applications in quantum computation and quantum sensing. We fabricated Archimedean Spiral Resonators (ASRs) using domain-matched epitaxially grown titanium nitride (TiN) on silicon wafers, achieving intrinsic quality factors of $Q_\mathrm{i} = (9.6 \pm 1.5) \times 10^6$ at the single-photon level and $Q_\mathrm{i} = (9.91 \pm 0.39) \times 10^7$ at high power, significantly outperforming traditional coplanar waveguide (CPW) resonators. We conducted a comprehensive numerical analysis using COMSOL to calculate surface participation ratios (PRs) at critical interfaces: metal-air, metal-substrate, and substrate-air. Our findings reveal that ASRs have lower PRs than CPWs, explaining their superior quality factors and reduced coupling to two-level systems (TLSs).