to save people poking around (because the linked article is quite appalling vague) - what you might call the "active part" of the gate is a single atom. that is surrounded by input, output, and gate connections and insulation that are all multiple-atoms in size. so the single, central phosphorous atom controls the flow from source to drain, depending on the gate voltage.
But as has already been mentioned, the biggest practical hurdle is temperature. This single atom device is measured at milliKelvin temperatures, and fundamentally could not operate at room temperature. It still has important consequences, but building computer chips is not an immediate one.
Making it work at room temperature is probably a greater long term issue. As the temperature goes up the system has a higher probability of accessing states that will make it not function properly (i.e. your logic gates become probabilistic.)
