Field demonstration of distributed quantum sensing without post-selection

TL;DR

This paper demonstrates practical distributed quantum sensing over 240 meters and 10 kilometers without post-selection, achieving sensitivity beyond the shot-noise limit in real-world field conditions.

Contribution

It presents the first field demonstration of unconditional distributed quantum sensing with entangled photons over significant distances, without relying on post-selection.

Findings

Unconditional violation of shot-noise limit up to 0.916 dB at 240 m

Successful quantum sensing over 10 km fiber with unknown parameters

Use of loophole-free Bell test setup with high heralding efficiency

Abstract

Distributed quantum sensing can provide quantum-enhanced sensitivity beyond the shot-noise limit (SNL) for sensing spatially distributed parameters. To date, distributed quantum sensing experiments have been mostly accomplished in laboratory environments without a real space separation for the sensors. In addition, the post-selection is normally assumed to demonstrate the sensitivity advantage over the SNL. Here, we demonstrate distributed quantum sensing in field and show the unconditional violation (without post-selection) of SNL up to 0.916 dB for the field distance of 240 m. The achievement is based on a loophole free Bell test setup with entangled photon pairs at the averaged heralding efficiency of 73.88%. Moreover, to test quantum sensing in real life, we demonstrate the experiment for long distances (with 10-km fiber) together with the sensing of a completely random and unknown parameter. The results represent an important step towards a practical quantum sensing network for widespread applications.