Fix is_parameterized() function of controlled gates

[AlbertJP]

Summary

Controlled gates are not recognised as parameterized by the is_parameterized() function. This causes issues in Aer and Algorithms when using circuits with controlled rotations: Qiskit/qiskit-aer#2323, qiskit-community/qiskit-algorithms#216

Details and comments

The is_parameterized() function reads from the _params variable, which is not set by some classes that override the params property, such as ControlledGate, CUGate, AnnotatedOperation and Initialize.

This pull request fixes is_parameterized(), such that it reads the params variable instead, which corresponds to the parameters of the base gate for controlled gates.

This pull request also adds a unit test and fixes an existing one.

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[AlbertJP]

The unit tests found another issue, the controlled gates in qiskit_aer.backends.name_mapping cannot be initialised anymore. (these did not get loaded when running tox locally, so I did not spot the issue before creating the PR.)

This is caused by commit doichanj/qiskit-aer@4587384 (pull request Qiskit/qiskit-aer#1995). I think this should be fixed on the Aer end?

[AlbertJP]

Some tests still fail as Qiskit/qiskit-aer#2326 is not yet merged.

I could change the unit test to test only a fixed list of subclasses, or read the __module__ attribute of the subclasses to exclude those from Aer - which feels like a quite ugly solution.

[mtreinish]

Some tests still fail as Qiskit/qiskit-aer#2326 is not yet merged.

I could change the unit test to test only a fixed list of subclasses, or read the __module__ attribute of the subclasses to exclude those from Aer - which feels like a quite ugly solution.

To be honest it's not super hacky, in this case I would view the failures as a testing harness bug. The intent of that test is to validate that all the ControlledGate instances in qiskit are correct. It pulling in other class definitions from other libraries that use qiskit is not the intent there and is not something that the test is intended to validate. I'd say updating the test harness to check that the leaf class being tested originates in qiskit is totally correct in this case.

[coveralls]

Pull Request Test Coverage Report for Build 13856089544

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2375 unchanged lines in 110 files lost coverage.
• Overall coverage increased (+1.1%) to 88.125%

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Files with Coverage Reduction	New Missed Lines	%
crates/accelerate/src/gate_direction.rs	1	97.14%
crates/qasm2/src/expr.rs	1	94.23%
qiskit/circuit/commutation_checker.py	1	94.12%
qiskit/circuit/library/standard_gates/r.py	1	97.56%
qiskit/circuit/library/standard_gates/rxx.py	1	97.73%
qiskit/circuit/library/standard_gates/rzx.py	1	97.73%
qiskit/circuit/library/standard_gates/u2.py	1	96.77%
qiskit/circuit/parameter.py	1	96.72%
qiskit/compiler/transpiler.py	1	98.61%
qiskit/primitives/utils.py	1	92.86%

Totals
Change from base Build 13649569641:	1.1%
Covered Lines:	72713
Relevant Lines:	82511

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💛 - Coveralls

[AlbertJP]

I have excluded the classes that start with qiskit_aer and now all tests pass.

It only tests classes that are direct subclasses of ControlledGate, but there are not so many interesting classes that are sub-subclasses, only non-parameterized and deprecated ones.