Default value of `meas_return` should be `single`.

Information

• Qiskit Terra version:
• Python version:
• Operating system:

What is the current behavior?

Currently default values of meas_level and meas_return are respectively set to 2 and avg. https://github.com/Qiskit/qiskit-terra/blob/fa09a7f6d2c6d6b35f8b221221264f7a437a5b17/qiskit/compiler/assemble.py#L30-L39

However meas_level=2 and meas_return='avg' are invalid combination and this error is caught by qobj validator in ibmq provider.

Steps to reproduce the problem

qobj = qiskit.assemble(some_schedule, backend)
backend.rund(qobj) # error raises here

What is the expected behavior?

invalid default setting should be replaced.

Suggested solutions

maybe one of below

1. change default meas_return to single
2. add validation in assembler
3. overwrite meas_return if meas_level is 2.

[taalexander]

This is a problem with the schemas. Both are required for the schemas to pass validation even in measurement level 2. The schemas would have to be updated to be conditional if this was to be fixed properly.

On Fri, Dec 20, 2019, 10:47 PM nkanazawa [e-mail] wrote:

I was using old master branch but the problem doesn’t happen now (I’m not sure the commit id causing problem), but I don’t think it is ignored.

import qiskit

qiskit.IBMQ.load_account()

provider = qiskit.IBMQ.get_provider(hub=‘‘, group=’’, project=‘‘) backend = provider.get_backend(’’)

qc = qiskit.QuantumCircuit(1, 1) qc.h(0) qc.measure(0, 0)

qobj = qiskit.assemble(qiskit.schedule(qiskit.transpile(qc, backend), backend), backend, meas_level=2)

then qobj.config says

meas_level=2, meas_lo_freq=[7.264856891, 7.070226896, 7.222414155, 7.130569974, 7.215856761, 6.979389665, 7.140246272, 7.034825806, 7.297209412, 7.097757684, 7.286899984, 7.054657786, 7.203657122, 7.153318307, 7.182410566, 6.975843032, 7.133222076, 7.018386448, 7.30700796, 7.104129811], meas_return=‘avg’ …

the combination of meas_level=2 and meas_return=‘avg’ may be ignored in our backend, but this is not true for other providers. is it is ignored, we should remove this from qobj.

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[taalexander]

Closing as this is not an issue as we do not plan to implement conditional JSON schemas. Extra parameters are fine to be ignored.