Acoustic spectral hole-burning in a two-level system ensemble

G Andersson,M Scigliuzzo,A L O Bilobran,P Delsing,J H Cole,M M De Lima

doi:10.1038/s41534-020-00348-0

Abstract

Microscopic two-level system (TLS) defects at dielectric surfaces and interfaces are among the dominant sources of loss in superconducting quantum circuits, and their properties have been extensively probed using superconducting resonators and qubits. We report on spectroscopy of TLSs coupling to the strain field in a surface acoustic wave (SAW) resonator. The narrow free spectral range of the resonator allows for two-tone spectroscopy where a strong pump is applied at one resonance, while a weak signal is used to probe a different mode. We map the spectral hole burnt by the pump tone as a function of frequency and extract parameters of the TLS ensemble. Our results suggest that detuned acoustic pumping can be used to enhance the coherence of superconducting devices by saturating TLSs.

Highlights

Two-level systems (TLSs) have attracted substantial interest in recent years[1,2] as they are among the most important sources of loss limiting the performance of superconducting quantum circuits[3,4,5,6,7,8]
Our measurements have revealed the shape of the spectral hole burnt in a TLS ensemble by a strong pump
We have shown that the response in acoustic susceptibility due to pumping is qualitatively well captured by theory based on the STM22, but find a deviation in the scaling of the extracted Rabi frequency with pump power

Summary

Introduction

Two-level systems (TLSs) have attracted substantial interest in recent years[1,2] as they are among the most important sources of loss limiting the performance of superconducting quantum circuits[3,4,5,6,7,8]. TLSs couple both to electromagnetic fields[4,5,11] and to strain[12,13,14] and recent approaches to investigating their behaviour typically involve measuring the lifetimes and resonance frequencies of superconducting resonators and qubits[6,7,8,15]. From experiments applying strain to superconducting qubit devices, there is an evidence that the same individual TLSs couple to both strain and electric field[12,18,19]. The strain associated with applied acoustic fields should probe the same ensemble as circuit electric fields

Methods

Results

Conclusion