QASM3 dupliacte qubit arguments

[rviktor85]

Environment

• Qiskit Terra version: 0.23.3
• Python version: 3.10
• Operating system: osx

What is happening?

I am trying to make convert and use QuantumCircuit from OpenQASM3 file. After obtaining the circuit (an instance of QuantumCircuit class), I added save_statevector() instruction and CircuitError: 'duplicate qubit arguments' error is thrown.

How can we reproduce the issue?

from qiskit.qasm3 import dumps, loads

circ = QuantumCircuit(2)
circ.x(0)
circ.cx(0, 1)

qasm_str = dumps(circ)
print(qasm_str)

new_circ = loads(qasm_str)
new_circ.save_statevector()

What should happen?

There shouldn't be any error thrown.

Any suggestions?

No response

[jakelishman]

Thanks for the report - this is actually a bug in Aer (which is what defines the save_statevector method) that's calculating the qubits in a circuit slightly incorrectly if there's overlapping registers. I'll transfer this issue over there so we can fix it.