Fix issue with deepcopy and builder API.

[kevinhartman]

Summary

Fixes an issue with QuantumCircuit.__deepcopy__'s handling of the scope builder API introduced in #10977.

Details and comments

The _OuterCircuitScopeInterface instance held in QuantumCircuit._builder_api contains a reference to the outer circuit, which appears to be an issue when performing a deepcopy (we end up with a duplicated circuit inside the scope instance).

To fix this, we construct a new _OuterCircuitScopeInterface for the deep copy instead.

Resolves #11610

[qiskit-bot]

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

• @Qiskit/terra-core

[jakelishman]

Ah thanks, yeah, it's obvious when you see it. Can we also add tests for shallow copy and pickle, here?

It'd be good to include some explicit assertions on exactly the clbits/cregs that should be present in both qc and qc2 after the deep copy/copy/pickle as well, to catch the potential failure case where both calls mutate both.

[coveralls]

Pull Request Test Coverage Report for Build 7731848487

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• 0 of 0 changed or added relevant lines in 0 files are covered.
• 205 unchanged lines in 30 files lost coverage.
• Overall coverage increased (+0.1%) to 89.6%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/circuit/parametervector.py	1	93.33%
qiskit/circuit/tools/pi_check.py	1	91.15%
qiskit/primitives/containers/data_bin.py	1	96.97%
qiskit/primitives/statevector_sampler.py	1	99.09%
qiskit/exceptions.py	2	93.75%
qiskit/primitives/containers/estimator_pub.py	2	97.47%
qiskit/primitives/containers/sampler_pub.py	2	96.92%
qiskit/providers/backend.py	2	79.73%
qiskit/providers/models/backendstatus.py	2	74.07%
qiskit/transpiler/passes/basis/basis_translator.py	2	97.64%

Totals
Change from base Build 7702053542:	0.1%
Covered Lines:	59404
Relevant Lines:	66299

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💛 - Coveralls

[kevinhartman]

@jakelishman

Ah thanks, yeah, it's obvious when you see it. Can we also add tests for shallow copy and pickle, here?

It'd be good to include some explicit assertions on exactly the clbits/cregs that should be present in both qc and qc2 after the deep copy/copy/pickle as well, to catch the potential failure case where both calls mutate both.

Good idea(s)! Done in ba9a32c.

[jakelishman]

Thanks for finding this, and the fix!

[jakelishman]

Wait sorry, I forgot I hadn't pushed the fix to the lint failure lol

[jakelishman]

That should keep pylint happy.