Deprecate execute()

[1ucian0]

Summary

The execute() function is as old as the SDK and it was always a high-level combinant function to say "here, a circuit, do your thing". That is exactly what Qiskit Primitives are about. Time to deprecated it.

Closes #7892
Closes #7640

[qiskit-bot]

One or more of the the following people are requested to review this:

• @Qiskit/terra-core

[mtreinish]

Do you want to call out the sampler here too? The BackendSampler class is fairly straightforward mapping to what execute() does (although imo execute() or transpile() followed by backend.run() are much easier to work with).

[1ucian0]

I added an example in 0367d40

[jakelishman]

(A minor note: CI's likely to be busy today, so if we're able to try and keep the number of commits we submit to CI down by doing more testing locally, it'll help keep the rc1 release more to time.)

[coveralls]

Pull Request Test Coverage Report for Build 6749790272

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• 182 unchanged lines in 20 files lost coverage.
• Overall coverage decreased (-0.06%) to 86.915%

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Files with Coverage Reduction	New Missed Lines	%
crates/qasm2/src/expr.rs	1	93.76%
qiskit/primitives/backend_sampler.py	1	98.84%
qiskit/transpiler/passes/optimization/normalize_rx_angle.py	1	97.96%
qiskit/primitives/base/base_primitive.py	3	90.32%
qiskit/primitives/estimator.py	3	95.06%
qiskit/primitives/sampler.py	3	95.77%
qiskit/pulse/library/waveform.py	3	93.75%
crates/qasm2/src/lex.rs	4	91.92%
qiskit/execute_function.py	4	77.78%
qiskit/circuit/init.py	5	85.29%

Totals
Change from base Build 6749032211:	-0.06%
Covered Lines:	74350
Relevant Lines:	85543

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💛 - Coveralls

[jakelishman]

Thanks for this, Luciano. A few more notes for consideration:

• in examples/python, there's still uses of execute. I don't know if we still even want to keep that folder, but if so, we probably ought to change them to at least be backend.run/transpile if not Sampler.
• test/randomized still has a couple of uses of execute
• the docstring of qiskit.quantum_info.analysis.distance.hellinger_fidelity still uses execute in an example

I noticed there's a few places in the tests where execute was replaced only with backend.run (no transpile), typically for BasicAer backends. I suspect that's probably a fine change and won't affect anything, just pointing it out. There's a few of those changes that have left a spurious seed_transpiler argument in backend.run, though, which it looks like BasicAer just ignores. We should probably tidy those up.

[jakelishman]

Not that I imagine it will matter here, but technically this is a behavioural change due to the missing transpile. Same comment for most changes in the next two files.

[jakelishman]

I wouldn't mind just changing these into simulated = Operator(qc), but this is also fine.

[1ucian0]

done in 6ef382a

[jakelishman]

This, and the other test in this file, set seed_transpiler which ideally needs moving into the transpile call.

[1ucian0]

indeed. Done in 2fa2580

[1ucian0]

Good catches!

• in examples/python, there's still uses of execute. I don't know if we still even want to keep that folder, but if so, we probably ought to change them to at least be backend.run/transpile if not Sampler.

Fixed in 39535b9

• test/randomized still has a couple of uses of execute

Fixed in 1bea14b

• the docstring of qiskit.quantum_info.analysis.distance.hellinger_fidelity still uses execute in an example

Fixed in 39535b9

I noticed there's a few places in the tests where execute was replaced only with backend.run (no transpile), typically for BasicAer backends. I suspect that's probably a fine change and won't affect anything, just pointing it out.

Yes. It was intentional for the cases where it was possible, as a way to minimize the changes.

There's a few of those changes that have left a spurious seed_transpiler argument in backend.run, though, which it looks like BasicAer just ignores. We should probably tidy those up.

done in 05dd686

[jakelishman]

I pushed up a couple more commits just to squash a couple more places I spotted, or places where we using a warning skip when Operator(qc) was just as easy.

I found one place that was skipping warnings for bind_parameters with a module='test\.python\.circuit\.test_parameters' (or something) that was causing an execute to get missed, but that's actually a good think - it shows the stacklevel was set correctly, otherwise it wouldn't have been skipped by that! (I fixed the skip by adding a regex match for messages mentioning the intended target.)

There's a couple of places that still use execute in tests along with other deprecated or dead code that's being tidied up elsewhere, so I've just left them. Let's get this into the merge queue.