# Rabi noise spectroscopy of individual two-level tunneling defects

## TL;DR

This study uses a superconducting qubit to perform Rabi spectroscopy on individual two-level tunneling defects, revealing how their dephasing rates depend on strain and defect interactions, advancing understanding of defect coherence.

## Contribution

It demonstrates a novel method to probe and manipulate single tunneling defects using Rabi oscillations, providing insights into their dephasing mechanisms and interactions.

## Key findings

- Dephasing rates scale quadratically with applied strain.
- Dephasing rates are inversely proportional to Rabi frequency.
- Pure dephasing is caused by interactions with incoherent low-frequency defects.

## Abstract

Understanding the nature of two-level tunneling defects is important for minimizing their disruptive effects in various nano-devices. By exploiting the resonant coupling of these defects to a superconducting qubit, one can probe and coherently manipulate them individually. In this work we utilize a phase qubit to induce Rabi oscillations of single tunneling defects and measure their dephasing rates as a function of the defect's asymmetry energy, which is tuned by an applied strain. The dephasing rates scale quadratically with the external strain and are inversely proportional to the Rabi frequency. These results are analyzed and explained within a model of interacting standard defects, in which pure dephasing of coherent high-frequency (GHz) defects is caused by interaction with incoherent low-frequency thermally excited defects.