Error to_matrix not defined for this

[cbjuan]

Sometimes we get this to_matrix not defined for this error. To reproduce this we can use the following code:

from qiskit_transpiler_service.ai.synthesis import AILinearFunctionSynthesis
from qiskit_transpiler_service.ai.collection import CollectLinearFunctions
from qiskit_transpiler_service.ai.routing import AIRouting
from qiskit.transpiler import PassManager
from qiskit.transpiler.preset_passmanagers import generate_preset_pass_manager
from qiskit_ibm_runtime import QiskitRuntimeService
from qiskit.circuit.library import EfficientSU2
import numpy as np

circuit = QuantumCircuit(4)
for i in range(4):
    circuit.h(i)
for i in range(3):
    circuit.rxx(np.pi/4, i, i+1)
    circuit.rzz(np.pi/3, i, i+1)
    circuit.cx(i, i+1)

runtime_service = QiskitRuntimeService()

backend_name = "ibm_sherbrooke"
backend = runtime_service.get_backend(backend_name)

# Base Qiskit lvl3 transpiler
lvl3_plus_ai = generate_preset_pass_manager(optimization_level=3, backend=backend) # Here you include your backend object (ibm_sherbrooke)

# We replace the base routing with the AI-routing
lvl3_plus_ai.layout = None
lvl3_plus_ai.routing = PassManager([
    AIRouting(backend_name=backend_name, optimization_level=3, layout_mode="optimize") # AI Routing
])

# We include synthesis as a post-routing process
lvl3_plus_ai.post_routing = PassManager([
    CollectLinearFunctions(),  # Collect linear functions
    AILinearFunctionSynthesis(backend_name=backend_name)  # Optimize linear functions
])

ai_transpiled_circ = lvl3_plus_ai.run(circuit)