# Quantum remote sensing of angular rotation of structured objects

## TL;DR

This paper demonstrates a quantum remote sensing method using entangled photons in orbital angular momentum to measure an object's angular rotation non-locally, with potential applications in noncontact and light-sensitive object sensing.

## Contribution

It introduces a novel noncontact angular rotation sensing technique using entangled OAM photons, advancing quantum remote sensing capabilities.

## Key findings

- Angular sensitivity is proportional to the OAM values of signal photons.
- The method enables nonlocal measurement of real object rotation.
- Potential for sensing light-sensitive specimens with different wavelength entangled photons.

## Abstract

Based on two-photon entanglement, quantum remote sensing enables the measurement and detection to be done non-locally and remotely. However, little attention has been paid to implement a noncontact way to sense a real objects angular rotation, which is a key step towards the practical applications of precise measurements with entangled twisted photons. Here, we use photon pairs entangled in orbital angular momentum (OAM) to show that a real object's angular rotation can be measured non-locally. Our experiment reveals that the angular sensitivity of the object encoded with idler photons is proportional to the measured OAM values of signal photons. It suggests potential applications in developing a noncontact way for angle remote sensing of an object with customized measurement resolution. Moreover, this feature may provide potential application in sensing of some light-sensitive specimens when the entangled photon pairs, which have significantly different wavelengths, are used, such as one photon is infrared but the other one is visible.