# Beating the Rayleigh Limit Using Two-Photon Interference

## TL;DR

This paper demonstrates that two-photon Hong-Ou-Mandel interference combined with spatial detection can surpass the Rayleigh limit by simultaneously estimating the separation and centroid of two point sources, both theoretically and experimentally.

## Contribution

It introduces a novel measurement scheme using two-photon interference to improve multiparameter imaging beyond classical limits.

## Key findings

- Achieved super-resolution in estimating source separation and centroid.
- Validated the method through experimental implementation.
- Surpassed traditional Rayleigh limit constraints.

## Abstract

Multiparameter estimation theory offers a general framework to explore imaging techniques beyond the Rayleigh limit. While optimal measurements of single parameters characterizing a composite light source are now well understood, simultaneous determination of multiple parameters poses a much greater challenge that in general requires implementation of collective measurements. Here we show, theoretically and experimentally, that Hong-Ou-Mandel interference followed by spatially resolved detection of photons provides precise information on both the separation and the centroid for a pair of point emitters, avoiding trade-offs inherent to single-photon measurements.