Simulation-Driven Analysis of Two-Level System (TLS) Loss in CPW Resonators

CPW) resonators offer a unique platform for analyzing material losses, particularly the two-level system (TLS) losses that occur at the single quantum excitation level in planar superconducting circuits. In this study, we used simulations to explore these TLS losses by evaluating the resonator quality factors (Q) under various interface modifications. By introducing low-loss materials of differing thicknesses and applying etching techniques to specific interfaces, we simulated a marked improvement in the quality factor. This result directly supports experimental findings that emphasize the benefits of air-interface modifications. Our simulations provide a comprehensive view of how these changes impact TLS losses, suggesting that modifying CPW resonator interfaces can significantly enhance device coherence and stability. This simulation-driven approach establishes a valuable framework for refining resonator design and fabrication, offering precise guidelines for TLS mitigation.