In-situ scanning gate imaging of individual two-level material defects in live superconducting quantum circuits

The low-temperature physics of structurally amorphous materials is governed by low-energy two-level system defects (TLS). Being impervious to much of traditional condensed matter probes, the exact origin and nature of TLS remain elusive. Recent advances towards realising stable high-coherence quantum computing platforms have increased the importance of studying TLS in solid-state quantum circuits, as they are a persistent source of decoherence and instability. In this talk, we will present a scanning gate microscopy technique at millikelvin temperatures, locating individual TLS in a live superconducting quantum circuit. Mapping and visualising the most detrimental TLS in the bath pinpoints the dominant sources of ubiquitous 1/f dielectric noise and energy relaxation. We also deduce the three-dimensional orientation of individual TLS electric dipole moments. Combining such insights with structural information of the underlying materials can help unravel the detailed microscopic nature and chemical origin of TLS, directing targeted strategies for their eventual mitigation.