  We propose a measure of entanglement that can be computed for any pure state
of an $M$-qubit system. The entanglement measure has the form of a distance
that we derive from an adapted application of the Fubini-Study metric. This
measure is invariant under local unitary transformations and defined as trace
of a suitable metric that we derive, the entanglement metric $\tilde{g}$.
Furthermore, the analysis of the eigenvalues of $\tilde{g}$ gives information
about the robustness of entanglement.
