  The nonclassicality of single-mode quantum states is studied in relation to
the entanglement created by a beam splitter. It is shown that properly defined
quantifications -- based on the quantum superposition principle -- of the
amounts of nonclassicality and entanglement are strictly related to each other.
This can be generalized to the amount of genuine multipartite entanglement,
created from a nonclassical state by an N splitter. As a consequence, a
single-mode state of a given amount of nonclassicality is fully equivalent, as
a resource, to exactly the same amount of entanglement. This relation is also
considered in the context of multipartite entanglement and multimode
nonclassicality.
