Entanglement detection and quantum metrology by Stokes photon diffraction imaging

TL;DR

This paper demonstrates that far field diffraction imaging of Stokes photons can detect spin entanglement and perform quantum metrology, enabling precise measurements of field gradients and system properties in cold atomic ensembles.

Contribution

It introduces a novel method using diffraction imaging of scattered photons for entanglement detection and quantum metrology in cold atomic systems.

Findings

Entanglement is witnessed by sharp diffraction peaks or dips.

Field gradients are measured via diffraction peak displacement.

Diffraction imaging enables non-demolition temperature and interaction monitoring.

Abstract

We show that far field diffraction image of spontaneously scattered Stokes photons can be used for detection of spin entanglement and for metrology of fields gradients in cold atomic ensembles. For many-body states with small or maximum uncertainty in spin-excitation number, entanglement is simply witnessed by the presence of a sharp diffraction peak or dip. Gradient vector of external fields is measured by the displacement of a diffraction peak due to inhomogeneous spin precessions, which suggests a new possibility for precision measurement beyond the standard quantum limit without entanglement. Monitoring temporal decay of the diffraction peak can also realize non-demolition probe of temperature and collisional interactions in trapped cold atomic gases. The approach can be readily generalized to cold molecules, trapped ions, and solid state spin ensembles.