Exponentiating a multi-controlled NOT gate for trotterization

Question

I am trying to exponentiate a multi-controlled NOT gate (MCX) via .exp_i() function for trotterization in Qiskit , but I cannot find such a gate represented in opflow. Is there a convenient way around it?

Answer 1

MCXGate exists in Qiskit's circuit library. So, you can get the operator as follows:

from qiskit.circuit.library import MCXGate
from qiskit.opflow import CircuitOp

num_ctrl_qubits = 3
ctrl_state = '111' # Optionally, set the control state
gate = MCXGate(num_ctrl_qubits, ctrl_state = ctrl_state)
mcx_op = CircuitOp(gate)

Now, you may call exp_i()

evolution_op = mcx_op.exp_i()