Acoustic spectral hole-burning in a two-level system ensemble

Microscopic two-level system (TLS) defects at dielectric surfaces and interfaces are among the dominant sources of loss in superconducting quantum circuits, their properties have been extensively probed using resonators qubits. We report on spectroscopy TLSs coupling to strain field a surface acoustic wave (SAW) resonator. The narrow free spectral range resonator allows for two-tone where strong pump is applied one resonance while weak signal used probe different mode. map hole burnt by tone as function frequency extract parameters TLS ensemble. Our results suggest that detuned pumping can be enhance coherence devices saturating TLSs.