  Entanglement is a unique nature of quantum theory and has tremendous
potential for application. Nevertheless, the complexity of quantum entanglement
grows exponentially with an increase in the number of entangled particles. Here
we introduce a quantum state concentration scheme which decomposes the
multipartite entangled state into a set of bipartite and tripartite entangled
states. It is shown that the complexity of the entanglement induced by the
large number of particles is transformed into the high dimensions of bipartite
and tripartite entangled states for pure quantum systems. The results not only
simplify the tedious work of verifying the (in)equivalence of multipartite
entangled states, but also are instructive to the quantum many-body problem
involving multipartite entanglement.
