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Fredkin gate

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description Fredkin gate Overview

The Fredkin gate, also known as the controlled swap gate, conditionally exchanges the values of two qubits based on the state of a control qubit, representing a fundamental logic operation in quantum computation.

help Fredkin gate FAQ

What does a Fredkin gate do to three bits or qubits?

A Fredkin gate uses one control input to conditionally swap the other two inputs. If the control is inactive, the target values stay in place; if it is active, the two target values exchange positions.

Why is the Fredkin gate also called a controlled swap gate?

The name describes its operation directly: a control signal decides whether a swap occurs. This makes the Fredkin gate a reversible logic operation used in discussions of quantum computation.

Is the Fredkin gate reversible?

Yes, applying the same controlled-swap operation again restores the original two target values. Reversibility is important because quantum gates must preserve information rather than erase it.

How is a Fredkin gate different from a simple NOT gate?

A NOT gate flips one bit, while a Fredkin gate conditionally exchanges two target bits based on a third control bit. Its three-input structure allows it to route information without discarding the original values.

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