Error when running final_index_layout(filter_ancillas=False)

[victor-villar]

Environment

• Qiskit version: 1.3.2
• Python version: 3.11
• Operating system: macos/linux

What is happening?

On certain circuits transpiled with a backend and a coupling map, this call fails

transpiled_circuit.layout.final_index_layout(filter_ancillas=False)

raising KeyError: "The item Qubit(QuantumRegister(5, 'q'), 3) does not exist in the Layout".

This worked fine until qiskit 1.3.0

How can we reproduce the issue?

Running the following code:

from qiskit import QuantumCircuit, transpile, qasm2
from qiskit_ibm_runtime import QiskitRuntimeService

service = QiskitRuntimeService(channel="ibm_quantum")
backend = service.backend("ibmq_manila")

qc = qasm2.loads('OPENQASM 2.0;include "qelib1.inc";qreg q[3];rccx q[2],q[1],q[0];t q[2];u(0.28905709212845454,5.626877140821112,5.481851443455051) q[1];h q[0];cx q[1],q[2];s q[0];', custom_instructions=qasm2.LEGACY_CUSTOM_INSTRUCTIONS)

transpiled_circuit = transpile(qc,backend=backend,coupling_map=[[0,1],[1,2],[2,3]],optimization_level=2,seed_transpiler=42)
transpiled_circuit.layout.final_index_layout(filter_ancillas=False)

What should happen?

There should not be any error in the call. The output to that particular example in qiskit 1.2.4 is [3, 1, 2, 0]

Any suggestions?

No response