Sampler (both V1 and V2) does not apply controlled parameterized rotations

[AlbertJP]

Informations

• Qiskit Aer version: 0.16.2
• Python version: 3.12.3
• Operating system: Ubuntu in WSL on Windows 11

What is the current behavior?

Controlled parameterized gates (like CRYGate) seem to be ignored when running the Sampler (V1 or V2).

Steps to reproduce the problem

from qiskit.circuit import QuantumCircuit, Parameter
import numpy as np
from qiskit_aer.primitives import Sampler
from qiskit_aer.primitives import SamplerV2

sampler = Sampler()
sampler_v2 = SamplerV2()

a = Parameter("a")
qc = QuantumCircuit(2)
qc.x(0)
qc.cry(a, 0, 1)
qc.x(0)

# Parameter list
params = [np.pi / 4]

qc_measured = qc.measure_all(inplace=False)

dist = sampler.run(qc_measured, params).result().quasi_dists
print("Dist V1", dist)

dist_v2 = sampler_v2.run([(qc_measured, params)]).result()[0].data.meas.get_counts()
print("Dist V2", dist_v2)

qc_bound = qc_measured.assign_parameters(params)

dist = sampler.run(qc_bound).result().quasi_dists
print("Dist V1", dist)

dist_v2 = sampler_v2.run([(qc_bound)]).result()[0].data.meas.get_counts()
print("Dist V2", dist_v2)

Result:

Dist V1 [{0: 1.0}]
Dist V2 {'00': 1024}
Dist V1 [{2: 0.14453125, 0: 0.85546875}]
Dist V2 {'00': 886, '10': 138}

What is the expected behavior?

Both circuits, the one with assigned parameters and the one without assigned parameters, should return similar values.

Suggested solutions

As shown in the example, this can be circumvented by assigning parameters before running the Sampler.

[AlbertJP]

It looks like the cause is on

qiskit-aer/qiskit_aer/backends/aerbackend.py

Line 125 in 37718fa

if instruction.operation.is_parameterized():

instruction.operation.is_parameterized() returns false for controlled rotations (see also Qiskit/qiskit#12624 (comment)).