Environment

• Qiskit version: 1.0
• Python version: 3.12
• Operating system: OSX and Linux

What is happening?

Recursively adding controls to an initial sub-circuit will cause Qiskit to hang, using up ever increasing CPU and memory resources. E.g. the below will never complete, but taking N=5 or so will.

N = 10
sub_qc = QuantumCircuit(1)
sub_qc.x(0)

out = QuantumCircuit(N)
out.compose(sub_qc,range(sub_qc.num_qubits), inplace=True)

for kk in range(N-1):
    sub_qc = sub_qc.control()
    out.compose(sub_qc,range(sub_qc.num_qubits), inplace=True)

How can we reproduce the issue?

Run above

What should happen?

It should not take apparently exponential time

Any suggestions?

No response