Reducing microwave loss in superconducting resonators due to trapped vortices

TL;DR

This paper demonstrates that etching a narrow slot into superconducting microwave resonators significantly reduces vortex-induced losses, thereby improving their quality factors in magnetic environments.

Contribution

It introduces a simple slot etching technique to enhance vortex pinning and reduce microwave loss in superconducting resonators.

Findings

Over tenfold reduction in vortex-related loss

Enhanced quality factors in magnetic fields

Effective vortex pinning without affecting resonator performance

Abstract

Microwave resonators with high quality factors have enabled many recent breakthroughs with superconducting qubits and photon detectors, typically operated in shielded environments to reduce the ambient magnetic field. Insufficient shielding or pulsed control fields can introduce vortices, leading to reduced quality factors, although increased pinning can mitigate this effect. A narrow slot etched into the resonator surface provides a straightforward method for pinning enhancement without otherwise affecting the resonator. Resonators patterned with such a slot exhibited over an order of magnitude reduction in the excess loss due to vortices compared with identical resonators from the same film with no slot.