# Entanglement-inspired frequency-agile rangefinding

## TL;DR

A new rangefinding system inspired by quantum entanglement works well in bright light and long distances with low power.

## Contribution

A classical energy-time correlated source that surpasses quantum illumination in brightness and noise reduction for practical rangefinding.

## Key findings

- Measured distance with 0.1 mm precision using 48 μW power over 154.8182 m.
- System works under varying solar background and weather conditions.
- Demonstrated noise reduction advantages over quantum illumination-based rangefinding.

## Abstract

Entanglement, a key feature of quantum mechanics, is recognized for its non-classical correlations which have been shown to provide significant noise resistance in single-photon rangefinding and communications. Drawing inspiration from the advantage given by energy-time entanglement, we developed an energy-time correlated source based on a classical laser that preserves the substantial noise reduction typical of quantum illumination while surpassing the quantum brightness limitation by over six orders of magnitude, making it highly suitable for practical remote sensing applications. A frequency-agile pseudo-random source is realized through fiber chromatic dispersion and pulse carving using an electro-optic intensity modulator. Operating at a faint transmission power of 48 μW, the distance between two buildings 154.8182 m apart can be measured with a precision better than 0.1 mm, under varying solar background levels and weather conditions with an integration time of only 100 ms. These trials verified the predicted noise reduction of this system, demonstrating advantages over quantum illumination-based rangefinding and highlighting its potential for practical remote sensing applications.

Quantum range finding struggles in bright background and at long distance. Here, the authors demonstrate a quantum-inspired, energy-time correlated classical rangefinder. It preserves quantum noise suppression, works at low power, and enables robust daylight remote ranging in real-world environments