How to add label to custom operator (from matrix) controlled gate?

Question

So here is what I'm trying to accomplish:

I have made a gate out of a matrix, with a control:

cG_p = Operator([[np.sqrt(p[j]), -np.sqrt(1-p[j])], [np.sqrt(1-p[j]), np.sqrt(p[j])]]).to_instruction().control(1)

I then append it to a circuit in a loop:

circ.append(cG_p, [j, j+1])

When I draw the circuit it by default labels the gate "Unitary". I want to put a custom label on the gate instead

I could put the custom label on when it wasn't a control (just a gate). That worked fine. Now that I've added the necessary control I can find no way to change the label.

Answer 1

Do you mean add a label for the gate that is controlled? If yes, you could just add it to the gate before controlling it:

>>> from qiskit.circuit import QuantumCircuit
>>> from qiskit.quantum_info import Operator
>>> gate = Operator([[1,0],[0,1]]).to_instruction()
>>> gate.label = "MyLabel"
>>> cgate = gate.control()
>>> circuit = QuantumCircuit(2)
>>> circuit.append(cgate, [0, 1])
>>> circuit.draw()

q_0: ─────■─────
     ┌────┴────┐
q_1: ┤ MyLabel ├
     └─────────┘