Single-Spin Spectrum-Analyzer for a Strongly Coupled Environment

TL;DR

This paper introduces a quantum-based spectral analysis method using a single trapped ion to detect and characterize strong, non-Gaussian discrete magnetic noise, with a novel three-step scheme and comparison of pulse sequences.

Contribution

It presents a new analytical model for spectral analysis of strongly coupled environments and a practical three-step noise characterization scheme for quantum probes.

Findings

Successful detection of non-Gaussian discrete magnetic noise.

Comparison shows differences between equidistant and Uhrig pulse schemes.

Method applicable to various quantum probes with coherent control.

Abstract

A qubit can be used as a sensitive spectrum analyzer of its environment. Here we show how the problem of spectral analysis of noise induced by a strongly coupled environment can be solved for discrete spectra. Our analytical model shows non-linear signal dependence on noise power, as well as possible frequency mixing, both are inherent to quantum evolution. This model enabled us to use a single trapped ion as a sensitive probe for strong, non-Gaussian, discrete magnetic field noise. To overcome ambiguities arising from the non-linear character of strong noise, we develop a three step noise characterization scheme: peak identification, magnitude identification and fine-tuning. Finally, we compare experimentally equidistant versus Uhrig pulse schemes for spectral analysis. The method is readily available to any quantum probe which can be coherently manipulated.