Logic gate used in reversible computation. Has 3 inputs:
  • Inputs A1 and A2 are control lines, and are copied unchanged to outputs A1' and A2'.
  • Input B is the data line; it is copied unchanged to output B' if A1= or A2=0, otherwise it is inverted on B'.
In conventional terms, A1'=A1, A2'=A2 and B'=B xor (A1 and A2).

The controlled controlled not gate is universal: you can build computers using just this gate.

Feynman notation:

A1 ---o---
A2 ---o---
B  ---x---

Abbreviation: CCN.