  We present a local hidden-variable model supplemented by classical
communication that reproduces the quantum-mechanical predictions for
measurements of all products of Pauli operators on an n-qubit GHZ state (or
"cat state"). The simulation is efficient since the required amount of
communication scales linearly with the number of qubits, even though there are
Bell-type inequalities for these states for which the amount of violation grows
exponentially with n. The structure of our model yields insight into the
Gottesman-Knill theorem by demonstrating that, at least in this limited case,
the correlations in the set of nonlocal hidden variables represented by the
stabilizer generators are captured by an appropriate set of local hidden
variables augmented by n-2 bits of classical communication.
