✨ Memory Option

What's the problem this feature will solve?

To whom it may concern,
First of all, I apologize if there are some misleading with the way I present the problem.

I was tying to simulate Simon's algorithm with the ddsim backend when I ran into a problem. I didn't know if it was a problem with the missing feature or the implementation I did.
This part is about calling the backend and getting the results:

backend = ddsim.DDSIMProvider().get_backend("qasm_simulator")
result = backend.run(transpiled_circuit, shots=num_shots, memory=True).result()

And here are the warning and error shown:

UserWarning: Option memory is not used by this backend
  result = backend.run(transpiled_circuit, shots=num_shots, memory=True).result()
Traceback (most recent call last):
  File "path/to/lib/python3.10/site-packages/qiskit/result/result.py", line 226, in get_memory
    memory = self.data(experiment)["memory"]
KeyError: 'memory'

Should the mentioned feature be implemented in the backend or am I doing something wrong?
Thanks in advance for your tips.

Describe the solution you'd like

If I understand correctly and the mentioned feature is added, the implementation of Simon's algorithm will be as easy as other Qiskit backends.

Start at the DDSIMProvider.get_backend("qasm_simulator") and backend.run(..., memory=True) usage shown in the report, then inspect how results are exposed to Qiskit. Compare the expected get_memory behavior with the current warning and missing "memory" result data; done means memory=True returns per-shot memory without the reported error, with coverage for this invocation.