@Marsmmz @diemilio @Dpbm I want feed back on this modified implementation of control function from source code of MCMT gate:

def control(self, num_ctrl_qubits=1, label=None, ctrl_state=None):
        """Return the controlled version of the MCMT circuit."""
        mcmt_circuit = QuantumCircuit(self.num_ctrl_qubits + num_target_qubits)
        if isinstance(ctrl_state, str):
            if ctrl_state == '0':  # If '0', apply X gates to all control qubits (0-controlled)
                for i in range(self.num_ctrl_qubits):
                    mcmt_circuit.x(i)
                mcmt_circuit.append(MCMT(self.gate, self.num_ctrl_qubits + num_ctrl_qubits, self.num_target_qubits), mcmt_circuit.qubits)
                for i in range(self.num_ctrl_qubits):
                    mcmt_circuit.x(i)
            elif ctrl_state == '1':  # If '1', do nothing special to MCMT (1-controlled)
                mcmt_circuit.append(MCMT(self.gate, self.num_ctrl_qubits + num_ctrl_qubits, self.num_target_qubits), mcmt_circuit.qubits)
            else:  # If string of '0's and '1's, handle accordingly
                for i in range(len(ctrl_state)):
                    if ctrl_state[i] == '0':
                        mcmt_circuit.x(i)
                mcmt_circuit.append(MCMT(self.gate, self.num_ctrl_qubits + num_ctrl_qubits, self.num_target_qubits), mcmt_circuit.qubits)
                for i in range(len(ctrl_state)):
                    if ctrl_state[i] == '0':
                        mcmt_circuit.x(i)

        return mcmt_circuit

In this version, if the ctrl_state is '0', X gates are applied to all the control qubits both before and after the MCMT gate, so we have a "0-controlled" MCMT. If ctrl_state is '1', the MCMT gate is implemented directly without any extra X gates, meaning it's a regular "1-controlled" MCMT. If ctrl_state is a string containing '0's and '1's, X gates are applied before and after the MCMT gate to the qubits corresponding to '0's in ctrl_state.

Also what additional test cases are needed apart from the default ones already present for MCMT ? One that I could think is to check length of ctrl_state string matches the length of control qubits if ctrl_state is not None.

add ctrl_state to MCMT gate #10698

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What should we add?

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