  We propose a procedure to identify and classify genuine tripartite
entanglement in pure 3-qubit states via the Activated Bipartite Entanglement
(ABE), which is defined here as the difference between the Entanglement of
Assistance and the Entanglement of Formation. We show that for pure states
belonging to one of the two inequivalent classes of genuine tripartite
entanglement, i.e., GHZ or W states, the ABE is always greater than zero. For
separable and biseparable states it is always null. In addition, our approach
is capable to distinguish between genuine tripartite entangled states, those
belonging to the GHZ class from those belonging to the W class. We also present
an experimental proposal, by using linear optical circuits and internal degrees
of freedom of a single photon, to measure the ABE and to verify the
characterization via activated entanglement. The circuit simulation shows an
excellent agreement with theoretical prediction for a wide class of GHZ and W
states.
