Measurement of the Noise Spectrum Using a Multiple-Pulse Sequence

TL;DR

This paper introduces a practical method to directly measure the noise spectrum affecting a qubit's phase coherence using multiple-pulse sequences, applicable across various noise environments.

Contribution

It presents a simple, experimentally accessible relationship between noise spectrum and qubit coherence time, valid for multiple noise types.

Findings

The method accurately captures the noise spectrum from experimental data.

It applies to classical, bosonic, and spin bath noise models.

The relationship holds universally across different qubit environments.

Abstract

A method is proposed for obtaining the spectrum for noise that causes the phase decoherence of a qubit directly from experimentally available data. The method is based on a simple relationship between the spectrum and the coherence time of the qubit in the presence of a pi-pulse sequence. The relationship is found to hold for every system of a qubit interacting with the classical-noise, bosonic, and spin baths.