# Separability criterion for three-qubit states with a four dimensional norm

## TL;DR

This paper introduces a new separability criterion for three-qubit states based on a four-dimensional norm derived from anti-diagonal entries, enabling easier determination of entanglement.

## Contribution

It provides a complete characterization of separability for states with only diagonal and anti-diagonal entries using a novel norm-based criterion.

## Key findings

- Norm computed explicitly in several cases
- Criterion allows routine separability checks
- Complete characterization for specific state classes

## Abstract

We give a separability criterion for three qubit states in terms of diagonal and anti-diagonal entries. This gives us a complete characterization of separability when all the entries are zero except for diagonal and anti-diagonals. The criterion is expressed in terms of a norm arising from anti-diagonal entries. We compute this norm in several cases, so that we get criteria with which we can decide the separability by routine computations.