Embedding NbN Nanowires Into Quantum Circuits With a Neon Focused Ion Beam

Parasitic two-level systems are generally present in superconducting circuits as a result of conventional fabrication and processing, and these lead to noise and loss of coherence in quantum systems. We examine the use of a Ne focused ion beam for producing nanowires integrated into superconducting circuits with a minimized density of parasitic two-level systems. We report measurements of nanowires produced by Ne focused-ion-beam milling in NbN resonators. The resonator losses increase after the nanowire is fabricated, with the $Q$ factor decreasing by ∼30% to ∼10 ⁵, which is a factor 10–100 higher than in the most closely comparable circuits previously measured. This indicates that the Ne focused ion beam is a promising route for creating superconducting-nanowire-based devices with low levels of decoherence.