Twin GHZ-states behave differently

TL;DR

This paper experimentally explores the properties of GHZ states and their mixtures in a hybrid photonic system, revealing how local geometrical relations influence entanglement and separability, with implications for quantum information processing.

Contribution

It demonstrates the construction and manipulation of a complete basis of GHZ-states in a hybrid photon system, highlighting their entanglement features and potential for quantum applications.

Findings

Mixing GHZ-states reveals different entanglement properties.

A specific GHZ-state has a twin state leading to full separability when mixed.

The experiment shows high fidelity and scalability in hybrid entanglement.

Abstract

Greenberger-Horne-Zeilinger (GHZ) states and their mixtures exhibit fascinating properties. A complete basis of GHZ-states can be constructed by properly choosing local basis rotations. We demonstrate this experimentally for the Hilbert space C2x4 by entangling two photons in polarisation and orbital angular momentum. Mixing GHZ-states unmasks different entanglement features based on their particular local geometrical connectedness. In particular, a specific GHZ-state in a complete orthonormal basis has a twin GHZ-state for which equally mixing leads to full separability in opposition to any other basis-state. Exploiting these local geometrical relations provides a toolbox for generating specific types of multipartite entanglement, each providing different benefits in outperforming classical devices. Our experiment, based on hybrid entangled entanglement, investigates these GHZs properties showing a good stability and fidelity and allowing a scaling in degrees of freedom and advanced operational manipulations.