The multi-controlled gate by RZGate().control() is less optimized.

[tamiyaonodera]

Environment

• Qiskit version: 1.3.0rc2
• Python version: 3.12.6
• Operating system: Sonoma 14.5

What is happening?

The multi-controlled gate by RZGate().control() is less optimized.

How can we reproduce the issue?

We create a circuit with a 6-qubit multi-controlled RZGate. We then transpile it to an Eagle device, and count the number of entangling gates.

from qiskit.transpiler.preset_passmanagers import generate_preset_pass_manager
backend = service.backend("ibm_sherbrooke")
pm = generate_preset_pass_manager(optimization_level=3, backend=backend, seed_transpiler=12345)

import numpy as np
from qiskit import QuantumCircuit, QuantumRegister
from qiskit.circuit.library import RZGate
n=6;  ang=np.pi/7
qr = QuantumRegister(n)
qc = QuantumCircuit(qr)
qc.append(RZGate(ang).control(n-1), qr)

isa_qc=pm.run(qc)
print(isa_qc.count_ops()['ecr'])

What should happen?

The above code outputs 266 in 1.3.0rc2, while 65 in 1.2.4.

Any suggestions?

No response

[tamiyaonodera]

I confirmed that this has not been fixed with 1.3.0. It outputs 266.

[mtreinish]

Yes, the fix merged on main and backported in preparation for a 1.3.1 release which will probably be published next week. You can try installing qiskit from source on the stable branch with: pip install 'git+https://github.com/Qiskit/qiskit@stable/1.3'. You will need the rust compiler installed to do this.