# Quantum-limited measurements of distance fluctuations with a multimode detector

## TL;DR

This paper introduces an experimental scheme using multimode detection and spectrally-resolved homodyne detection to measure multiple phase-encoded parameters of light simultaneously, achieving quantum-limited sensitivity.

## Contribution

It presents a novel multimode measurement approach that allows simultaneous extraction of multiple parameters encoded in light with quantum-limited precision.

## Key findings

- Achieved shot-noise limited sensitivity in pulse delay measurement.
- Successfully extracted dispersion value of a dispersive medium.
- Demonstrated simultaneous multi-parameter measurement with a single setup.

## Abstract

An experimental scheme is introduced to measure multiple parameters that are encoded in the phase quadrature of a light beam. Using a modal description and a spectrally-resolved homodyne detection, it is shown that all of the information is collected simultaneously, such that a single measurement allows extracting the value of multiple parameters \emph{post-facto}. With a femtosecond laser source, we apply this scheme to a measurement of the delay between two pulses with a shot-noise limited sensitivity as well as extracting the dispersion value of a dispersive medium.