Billiard-ball computer

Realizes: reversible boolean logic (Fredkin gate)

Proposed by Fredkin & Toffoli (1982). Balls travel on paths representing wires; presence/absence of a ball encodes a bit. Collisions at path intersections implement logic gates. Logically and thermodynamically reversible — no information is destroyed. Speed: nanoseconds to microseconds (ball velocity dependent). Capacity: arbitrary boolean circuits (theoretically universal).

Examples

Default Billiard-ball computer implementation

Basic implementation

AND OR NOT FANOUT seconds unbounded pJ