Characterization of four-qubit states via Bell inequalities

TL;DR

This paper introduces Bell inequalities that classify four-qubit entanglement types using only two measurement settings per observer, including a quadratic inequality for these systems.

Contribution

It presents a new set of Bell inequalities capable of fully characterizing various separability classes of four-qubit states with minimal measurement settings.

Findings

Classifies fully separable, bi-separable, and tri-separable states

Derives a quadratic Bell inequality for four-qubit systems

Provides tools for entanglement detection in four-qubit states

Abstract

A set of Bell inequalities classifying the quantum entanglement of four-qubit states is presented. These inequalities involve only two measurement settings per observer and can characterize fully separable, bi-separable and tri-separable quantum states. In addition, a quadratic inequality of the Bell operators for four-qubit systems is derived.