Transmission-line resonators for the study of individual two-level tunneling systems

TL;DR

This paper introduces a novel superconducting transmission-line resonator setup that enables detailed study of individual two-level tunneling systems (TLS) and their collective effects, advancing understanding of noise sources in quantum devices.

Contribution

The work presents a new experimental platform that allows for the manipulation and measurement of individual TLS properties and their ensemble behavior in amorphous dielectrics.

Findings

Strong coupling between TLS and resonator observed

TLS-induced frequency fluctuations and phase noise characterized

Insights into TLS interactions and spectral diffusion obtained

Abstract

Parasitic two-level tunneling systems (TLS) emerge in amorphous dielectrics and constitute a serious nuisance for various microfabricated devices, where they act as a source of noise and decoherence. Here, we demonstrate a new test bed for the study of TLS in various materials which provides access to properties of individual TLS as well as their ensemble response. We terminate a superconducting transmission-line resonator with a capacitor that hosts TLS in its dielectric. By tuning TLS via applied mechanical strain, we observe the signatures of individual TLS strongly coupled to the resonator in its transmission characteristics and extract the coupling components of their dipole moments and energy relaxation rates. The strong and well-defined coupling to the TLS bath results in pronounced resonator frequency fluctuations and excess phase noise, through which we can study TLS ensemble effects such as spectral diffusion, and probe theoretical models of TLS interaction.