Apply the action of this circuit upon a state.

        If no initial state provided an initial zero state will be created.

def run(self, ket: State = None) -> State:
        """
        Apply the action of this circuit upon a state.

        If no initial state provided an initial zero state will be created.
        """
        if ket is None:
            qubits = self.qubits
            ket = zero_state(qubits=qubits)

        for elem in self.elements:
            ket = elem.run(ket)
        return ket