Dielectric surface loss in superconducting resonators with flux-trapping holes

TL;DR

This study investigates how flux-trapping holes in superconducting resonators affect dielectric TLS loss, finding a small increase near the holes and negligible magnetic loss contribution, informing design choices for quantum circuits.

Contribution

It provides the first detailed measurement of dielectric TLS loss increase due to flux-trapping holes and estimates magnetic loss contributions in superconducting resonators.

Findings

Dielectric TLS loss increases by ~25% when holes are within 2 μm of the resonator edge.

Holes further away from the edge do not significantly affect dielectric loss.

Magnetic loss contribution is negligible at magnetic fields up to 5 μT.

Abstract

Surface distributions of two level system (TLS) defects and magnetic vortices are limiting dissipation sources in superconducting quantum circuits. Arrays of flux-trapping holes are commonly used to eliminate loss due to magnetic vortices, but may increase dielectric TLS loss. We find that dielectric TLS loss increases by approximately 25% for resonators with a hole array beginning 2 $\mu \text{m}$ from the resonator edge, while the dielectric loss added by holes further away was below measurement sensitivity. Other forms of loss were not affected by the holes. Additionally, we estimate the loss due to residual magnetic effects to be $9\times 10^{-10} /\mu\text{T} $ for resonators patterned with flux-traps and operated in magnetic fields up to $5$ $\mu\text{T}$. This is orders of magnitude below the total loss of the best superconducting coplanar waveguide resonators.