Tunable Nb superconducting resonators based upon a Ne-FIB-fabricated constriction nanoSQUID

TL;DR

This paper presents a method to create tunable, high-Q niobium superconducting resonators with magnetic field resilience using neon FIB-patterned constriction nanoSQUIDs, suitable for hybrid spin systems.

Contribution

It introduces a novel fabrication technique for Nb resonators with tunability and high magnetic field resilience using neon FIB-patterned constriction nanoSQUIDs.

Findings

Achieved high quality factor in Nb resonators.

Demonstrated frequency tunability under magnetic fields.

Showed potential for coupling to spin systems.

Abstract

Hybrid superconducting--spin systems offer the potential to combine highly coherent atomic quantum systems with the scalability of superconducting circuits. To fully exploit this potential requires a high quality-factor microwave resonator, tunable in frequency and able to operate at magnetic fields optimal for the spin system. Such magnetic fields typically rule out conventional Al-based Josephson junction devices that have previously been used for tunable high-$Q$ microwave resonators. The larger critical field of niobium (Nb) allows microwave resonators with large field resilience to be fabricated. Here, we demonstrate how constriction-type weak links, patterned in parallel into the central conductor of a Nb coplanar resonator using a neon focused ion beam (FIB), can be used to implement a frequency-tunable resonator. We study transmission through two such devices and show how they realise high quality factor, tunable, field resilient devices which hold promise for future applications coupling to spin systems.