Strain-spectroscopy of strongly interacting defects in superconducting qubits

TL;DR

This paper offers a theoretical framework to understand the spectral response of strongly interacting tunneling two-level-systems in superconducting qubits, aiding experimental identification and characterization of these defects.

Contribution

It provides a simple theoretical model to interpret strain-assisted spectroscopy of interacting TLS within superconducting qubits.

Findings

Spectral signatures of strongly interacting TLS can be predicted theoretically.

The model helps distinguish different states of TLS in experimental spectra.

Insights can improve the understanding and mitigation of defect-related decoherence.

Abstract

The proper functioning of some micro-fabricated novel quantum devices, such as superconducting resonators and qubits, is severely affected by the presence of parasitic structural material defects known as tunneling two-level-systems (TLS). Recent experiments have reported unambiguous evidence of the strong interaction between individual (coherent) TLS using strain-assisted spectroscopy. This work provides an alternative and simple theoretical insight that illustrates how to obtain the spectral response of such strongly interacting defects residing inside the amorphous tunnel barrier of a qubit's Josephson junction. Moreover, the corresponding spectral signatures obtained here may serve to quickly and efficiently elucidate the actual state of these interacting TLS in experiments based on strain- or electric-field spectroscopy.