Modeling Kinetic Inductance in Superconductors: A Practical Guide
应用文章
Accurate modeling of superconducting materials is critical for designing high-performance microwave circuits used in quantum computing and quantum sensing applications. Unlike conventional conductors, superconductors exhibit temperature-dependent kinetic inductance, which can significantly influence resonant frequency, impedance, and overall circuit behavior — especially in thin-film structures where kinetic inductance may represent a substantial portion of total inductance.
This application note demonstrates how Keysight ADS provides a physics-based workflow for superconducting circuit simulation by defining materials through key physical properties, including critical temperature (Tc), London penetration depth (λL(0)), and normal-state conductivity or sheet resistance (σn/Rs). Rather than relying on manual impedance adjustments, ADS automatically calculates superconducting kinetic inductance and surface impedance effects for both circuit-level and electromagnetic (EM) simulations.
Using a coplanar waveguide (CPW) resonator example, the application note explores how temperature variations impact superconducting device performance. The results show that changes in kinetic inductance with temperature can cause significant resonant frequency shifts, potentially reaching several gigahertz. These effects must be accurately modeled to ensure reliable quantum circuit design and optimization.
The note also compares analysis approaches within ADS, including fast circuit simulation for early design exploration and QuantumPro EM simulation for geometry-accurate predictions. Full EM analysis and Energy Participation Analysis (EPA) demonstrate how material properties and physical layout interact to determine resonator behavior.
By combining material-based superconducting models, circuit simulation, and advanced EM analysis, Keysight ADS provides a unified environment for designing and validating superconducting microwave structures. This workflow helps engineers account for real-world material behavior, improve simulation accuracy, and accelerate development of quantum technologies requiring precise control of superconducting devices.