What is the controlled-controlled-controlled-U gate?

What is the controlled-controlled-controlled-U gate?

The controlled-controlled-controlled-U gate, also known as the Toffoli gate, is a three-qubit gate in quantum computing. It performs a controlled-U operation on the target qubit if and only if both control qubits are in the state |1⟩. Otherwise, it leaves the target qubit unchanged. The controlled-U operation can be any single-qubit gate, allowing for various quantum computations and algorithms to be implemented.