Direct Spectroscopy of Ensemble Material Defect Behavior using 3D Waveguide and Microwave Combs

Two-level systems (TLS) in amorphous materials are the primary source of loss for superconducting qubits. Various studies have characterized these TLSs indirectly by measuring the T₁ times of superconducting qubits as a function of frequency. This work introduces a novel approach based on a broadband 3D aluminum waveguide where we directly measure TLS loss across the pass band of the waveguide. Our approach is entirely modular, meaning samples can be removed for further processing and characterization to enable longitudinal material studies. To improve our acquisition times and probe coherent processes in our TLS ensemble, we utilize frequency combs directly generated from an RFSoC (Radio Frequency System-on-Chip) board using QICK (Quantum Instrumentation Control Kit). Here, we will present measurements of the dynamics of an ensemble of TLSs using this platform and provide an outlook for future experiments.