Spectrum and separability of mixed 2-qubit X-states

TL;DR

This paper classifies separable mixed 2-qubit X-states based on spectral degeneracies, revealing four distinct classes with specific dimensionalities and properties.

Contribution

It provides a detailed classification of separable 2-qubit X-states according to their spectral degeneracies, identifying four unique classes.

Findings

Four classes of separable X-states identified

Classification based on spectrum degeneracies

Specific dimensionalities for each class

Abstract

The separable mixed 2-qubit X-states are classified in accordance with degeneracies in the spectrum of density matrices. It is shown that there are four classes of separable X-states, among them: one 4D family, a pair of 2D family and a single, zero-dimensional maximally mixed state.