feature: Added counts based on operator name and qubits specified

[ACE07-Sev]

Issue #, if available: Closes #1235

Description of changes:
Added instruction counting to Circuit with additional filtering based on specific gate name and/or qubits applied to.

Testing done:
Added a unit tester to test_circuit.py which asserts the desired behavior, and ensures a ValueError is raised for out of bounds qubits specified.

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[ACE07-Sev]

I added the qubit specifier you requested, but not quite sure what you meant by density of operators. If you can kindly guide me on that, I can add that as well today.

[ACE07-Sev]

@sesmart Can I please get a review?

[sesmart]

Hi @ACE07-Sev , @aniksd-braket will be reviewing this issue.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a5ee47d) to head (5d8d274).

Additional details and impacted files

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##              main     #1275   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          169       169           
  Lines        10963     10975   +12     
  Branches      1412      1416    +4     
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+ Hits         10963     10975   +12     

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[jaimeajl]

This looks like a useful direction. I think the “operator density” stretch goal from the issue could be implemented as a small complementary layer on top of raw instruction counts.

My interpretation would be a deterministic circuit summary that includes both counts and normalized densities, for example:

• total instruction count
• count by operator name
• count filtered by qubits
• operator density: operator_count / total_instruction_count
• per-qubit instruction count
• per-qubit instruction density

This would make the feature useful not only as a convenience method, but also for benchmarking, sanity checks, and comparing generated or transformed circuits.

A possible output shape could be:

{
"total": 10,
"by_operator": {"h": 2, "cnot": 3, "rz": 5},
"operator_density": {"h": 0.2, "cnot": 0.3, "rz": 0.5},
"per_qubit": {0: 6, 1: 4},
"per_qubit_density": {0: 0.6, 1: 0.4}
}

If this interpretation aligns with the maintainers’ expectations, I can open a focused follow-up PR for the density/summary part, without duplicating the existing count implementation.

[ACE07-Sev]

@jaimeajl may I ask if you're part of the maintainer team?

[ACE07-Sev]

@aniksd-braket Can I please get a review?

[aniksd-braket]

Would be great if you could also add the case of getting counts for of operations on all qubits specified, instead of just any of the qubits specified

[aniksd-braket]

Would the output be an empty dictionary if a qubit exists in the circuit but has no operation? Could you add a test for this case?

[ACE07-Sev]

You mean if I have this

from braket.circuits import Circuit

circuit = Circuit().h(0).cnot(0, 2)
print(circuit.count(qubits={1}))

and wondering what will return for this?

[ACE07-Sev]

@aniksd-braket

[aniksd-braket]

Here do you consider all operators, including noise operations?

[ACE07-Sev]

Any instruction applied to the circuit (if we go with just ones applied to qubits then gphase would need to be skipped I suppose). Are there exclusions you want me to skip?

[ACE07-Sev]

Greetings @aniksd-braket

Thank you very much for the review. Sure thing, I'll get to it first thing in the morning.