Multipartite Entanglement classes via Negativity Fonts*

The number and types of K-way negativity fonts in canonical form of an N-qubit state depends on the nature and amount of quantum coherences in the state. Non zero determinants of negativity fonts, characterizing a given state, are easily written down and reflect the entanglement microstructure of the superposition. A classification criterion for multipartite entangled states, based on negativity fonts in canonical state and decomposition of global partial transpose in terms of K-way partially transposed operators, is proposed. Inequivalent sub-classes are labelled by N-qubit local unitary invariants. A complete classification of four qubit states is obtained. The number of major families for N$>$3 is found to be $2^N-2N$. Classification of four qubit states indicates that a small number of relevant polynomial invariants is enough to classify N-qubit states.