Low Loss Hybrid Nb/Au Superconducting Resonators for Quantum Circuit Applications

Abstract Superconducting resonators are critical components in a wide range of quantum technologies, including high‐performance detectors and amplifiers. However, their performance is often limited by noise and sensitivity issues caused by two‐level systems (TLS) originated from oxide layers, such as , in the device. To address this challenge, a superconducting device combining a 100 nm niobium (Nb) circuit with a 10 nm gold (Au) capping layer is investigated. This study explores the device's performance across a wide range of temperatures and driving powers. Comparing with an uncapped device, it is demonstrated that the Au capping layer effectively avoids oxide formation, thus reducing the TLS density and increasing the internal quality factors. Moreover, an increase in the non‐linearity response is also observed. These findings provide valuable insights into improving resonator performance by addressing material‐specific limitations, paving the way for more robust and efficient superconducting devices and highlight the potential of Nb/Au lumped element resonators for applications where TLS noise mitigation is critical.