Probing High Frequency Noise with Macroscopic Resonant Tunneling

TL;DR

This paper introduces a method to characterize high-frequency noise in flux qubits using macroscopic resonant tunneling, revealing an ohmic environment up to 4 GHz and modeling complex noise spectra.

Contribution

The authors develop a novel technique to extract high-frequency noise spectral density from MRT measurements and derive a comprehensive lineshape model for broadband and low-frequency noise.

Findings

Noise spectral density is consistent with an ohmic environment up to 4 GHz.

The hybrid noise model fits experimental data well across various conditions.

The method enables detailed noise characterization in superconducting qubits.

Abstract

We have developed a method for extracting the high-frequency noise spectral density of an rf-SQUID flux qubit from macroscopic resonant tunneling (MRT) rate measurements. The extracted noise spectral density is consistent with that of an ohmic environment up to frequencies ~ 4 GHz. We have also derived an expression for the MRT lineshape expected for a noise spectral density consisting of such a broadband ohmic component and an additional strongly peaked low-frequency component. This hybrid model provides an excellent fit to experimental data across a range of tunneling amplitudes and temperatures.