Entanglement-enhanced probing of a delicate material system

TL;DR

This paper demonstrates the first entanglement-enhanced measurement of a delicate material system, surpassing the standard quantum limit using NOON states, enabling ultra-gentle probing of sensitive quantum and biological systems.

Contribution

It introduces a novel method of using atom-resonant NOON states for non-destructive, entanglement-enhanced sensing of delicate materials, overcoming loss and noise limitations.

Findings

Achieved over five standard deviations sensitivity improvement

Demonstrated quantum enhancement with realistic loss and noise

Enabled ultra-gentle probing of sensitive quantum and biological systems

Abstract

Quantum metrology uses entanglement and other quantum effects to improve the sensitivity of demanding measurements. Probing of delicate systems demands high sensitivity from limited probe energy and has motivated the field's key benchmark-the standard quantum limit. Here we report the first entanglement-enhanced measurement of a delicate material system. We non-destructively probe an atomic spin ensemble by means of near-resonant Faraday rotation, a measurement that is limited by probe-induced scattering in quantum-memory and spin-squeezing applications. We use narrowband, atom-resonant NOON states to beat the standard quantum limit of sensitivity by more than five standard deviations, both on a per-photon and per-damage basis. This demonstrates quantum enhancement with fully realistic loss and noise, including variable-loss effects. The experiment opens the way to ultra-gentle probing of single atoms, single molecules, quantum gases and living cells.