Universal bound on microwave dissipation in superconducting circuits

TL;DR

This paper establishes an empirical scaling law linking microwave dissipation in superconductors to superfluid density, revealing an intrinsic bulk dissipation limit affecting quantum circuit coherence.

Contribution

It uncovers a universal bulk dissipation channel related to nonequilibrium quasiparticles, independent of surface losses, across diverse superconducting materials and device geometries.

Findings

Identifies a scaling relation between dissipation and superfluid density.

Reveals an intrinsic dissipation mechanism due to trapped quasiparticles.

Provides a basis for selecting materials to optimize quantum coherence.

Abstract

Improving the coherence of superconducting qubits is essential for advancing quantum technologies. While superconductors are theoretically perfect conductors, they consistently exhibit residual energy dissipation when driven by microwave currents, limiting coherence times. Here, we report an empirical scaling relation between microwave dissipation and the superfluid density, a bulk property of superconductors related to charge carrier density and disorder. Our analysis spans a wide range of superconducting materials and device geometries, from highly disordered amorphous films to ultra-clean systems with record-high quality factors, including resonators, 3D cavities, and transmon qubits. This scaling reveals an intrinsic bulk dissipation channel, independent of surface dielectric losses, which we attribute to nonequilibrium quasiparticles trapped within disorder-induced spatial variations of the superconducting gap, with a density set by a universal material parameter. Our findings identify an empirical coherence limit associated with intrinsic material properties and provide a data-driven basis for materials selection in future superconducting quantum circuits.