Fredkin gate

That is, each cell can be implemented by a multiplexer, and is closely related in its operation to a Fredkin gate.

The computation via reversible operations as the Fredkin gate can be implemented in vector logic.

The 3-input Fredkin gate is functionally complete reversible gate by itself - a sole sufficient operator.

The Fredkin gate is a reversible 3-bit gate that swaps the last two bits if the first bit is 1; a controlled-swap operation.

He is the inventor of the trie data structure, the Fredkin gate and the Billiard-Ball Computer Model for reversible computing.

While Konrad Zuse's book, Calculating Space (1969), mentioned the importance of reversible computation, the Fredkin gate represented the essential breakthrough.

This is done with the following quantum circuit which uses one Fredkin gate F, one Hadamard gate H and an ancilla qubit a.

It is easy to see that the Fredkin gate is universal, since it can be used to implement AND and NOT:

Examples of these logic gates which have been studied are the controlled NOT gate (also called CNOT gate), the Toffoli gate and the Fredkin gate.