Simple demonstrations of 2 atom transistors have already been done (search for Rydberg blockade rubidium transistors). Practical applications are very, very fa

Simple demonstrations of 2 atom transistors have already been done (search for Rydberg blockade rubidium transistors). Practical applications are very, very far away. A single collision with a molecule of air is plenty to dislodge an atom from any given internal state. Demonstrations are all run in vacuum chambers and rely on control of an atom's internal state.