Sorry for unintentional plagiarism, because the ANT gate from previous post is an analogue of “billiard ball switch gate” represented, e.g, on page 16 fig.16 of Conservative Logic by Fredkin and Toffoli (1982). The schematic construction of Fredkin gate from such gates is also known and in the paper represented a picture due to R. Feynman and A. Ressler. Ashamed by such a omission in my previous post I even spent some time for construction of such a gate with “ants.”
The construction looks rather complicated due necessity of synchronization of ants motion. 
In fact, the animated gif represents identical input – output (0,1,1)→(0,1,1) and (1,1,1)→(1,1,1), because the nontrivial exchange transformation (1,0,1)↔(1,1,0) requires period of gif animation in two times longer and it may be a problem for slow computers. Anyway, despite of triviality of transformation the animation shows all possible roads, e.g., it may be mentioned that ants representing two last units in (1,1,1)→(1,1,1) exchange positions due to four interactions with the first ant, but (0,1,1)→(0,1,1) does not cause such interactions and swap.
Quantum Bot 