  Operation parameters of magnetic quantum cellular automata are evaluated for
the purposes of reliable logic operation. The dynamics of the nanomagnets is
simulated via the Landau-Lifshitz-Gilbert equations with a stochastic magnetic
field corresponding to thermal fluctuations. It is found that in the macrospin
approximation the switching speed does not change under scaling of both size
and distances between nanomagnets. Thermal fluctuations put a limitation on the
size of nanomagnets, since the gate error rate becomes excessive for
nanomagnets smaller than 200nm at room temperature.
