Performance of Magnetic Quantum Cellular Automata and Limitations Due to Thermal Noise

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: when we consider a majority gate that features a biaxial anisotropy as a stabilizing mechanism and a uniform clocking field, the gate error rate becomes excessive for nanomagnets smaller than about 200 nm at room temperature.