  In this paper, we characterize the maximal violation of Ardehali's inequality
of $n$ qubits by showing that GHZ's states and the states obtained from them by
local unitary transformations are the unique states that maximally violate the
Ardehali's inequalities. This concludes that Ardehali's inequalities can be
used to characterize maximally entangled states of $n$ qubits, as the same as
Mermin's and Bell-Klyshko's inequalities.
