# Reconstructing nonlinearities with intermodulation spectroscopy

## TL;DR

This paper introduces a spectroscopic method to reconstruct nonlinearities in high-Q harmonic oscillators by analyzing intermodulation spectra, enhancing information extraction without increasing detection bandwidth.

## Contribution

The paper presents a novel analysis technique that reconstructs oscillator nonlinearities from intermodulation spectra, improving measurement sensitivity and information content.

## Key findings

- Effective reconstruction of nonlinearities from spectral data
- Enhanced measurement sensitivity near resonance
- Reduced detector noise impact

## Abstract

We describe a method of analysis which allows for reconstructing the nonlinear disturbance of a high Q harmonic oscillator. When the oscillator is driven with two or more frequencies, the nonlinearity causes intermodulation of the drives, resulting in a complicated spectral response. Analysis of this spectrum allows one to approximate the nonlinearity. The method, which is generally applicable to measurements based on resonant detection, increases the information content of the measurement without requiring large detection bandwidth, and optimally uses the enhanced sensitivity near resonance to extract information and minimize error due to detector noise.