  The information obtained from the operation of a quantum gate on only two
complementary sets of input states is sufficient to estimate the quantum
process fidelity of the gate. In the case of entangling gates, these conditions
can be used to predict the multi qubit entanglement capability from the
fidelities of two non-entangling local operations. It is then possible to
predict highly non-classical features of the gate such as violations of local
realism from the fidelities of two completely classical input-output relations,
without generating any actual entanglement.
