Towards individual TLS detection by scanning gate microscopy

Superconducting circuits have emerged as a promising platform for quantum computations and quantum sensing applications. However, superconducting circuits are persistently plagued by challenges related to decoherence and losses caused by two-level system (TLS) defects. Hence, understanding their origin, properties, location and ultimately mitigating these defects will play a central role in realizing superconducting circuits capable of long-term storage and manipulation of quantum states. In this talk, we will present a novel technique to detect, measure and image individual TLS defects in operational superconducting quantum circuits. We will first briefly discuss the challenges and complexities of incorporating a custom-built scanning probe microscope in a mK dry fridge while maintaining a coherent environment for operating superconducting circuits, followed by our protocol for TLS detection with a sharp AFM tip. Our results open a new avenue for a systematic exploration of individual TLS defects in superconducting circuits and demonstrates a path forward to study their spatial distribution, physical structures, and chemical compositions.