Enhancement cirq preprocessing by feelerx · Pull Request #248 · qBraid/qbraid-qir

feelerx · 2025-10-25T08:40:03Z

Refactor circuit preprocessing to use Cirq's `optimize_for_target_gateset`

Closes #93

Summary

This PR refactors the circuit preprocessing pipeline to use Cirq's built-in optimize_for_target_gateset transformer instead of manual try-except decomposition logic.
This improves code quality, performance, and maintainability.

Changes

Core Implementation

Created QirTargetGateSet class extending cirq.TwoQubitCompilationTargetGateset to define QIR-supported gates
Replaced manual gate-by-gate decomposition with cirq.optimize_for_target_gateset
Removed _decompose_gate_op and _decompose_unsupported_gates helper functions
Simplified preprocess_circuit to use the new gateset-based approach

Key Features

Selective decomposition: Only unsupported gates are decomposed; gates already in the target set (H, X, Y, Z, CNOT, CZ, SWAP, TOFFOLI, measurements) are preserved
TOFFOLI preservation: Overridden preprocess_transformers to prevent automatic decomposition of 3-qubit TOFFOLI gates
Conditional operation support: Circuits containing ClassicallyControlledOperation bypass full optimization to avoid unitary merge errors
Backward compatibility: Added _add_rads_attribute transformer to maintain _rads field on rotation gates for downstream QIR visitor

Implementation Details

The QirTargetGateSet implements custom decomposition methods:

_decompose_single_qubit_operation: Handles single-qubit gates, preserving supported gates and decomposing others via unitary matrix
_decompose_two_qubit_operation: Handles two-qubit gates, decomposing to CZ operations when needed
_decompose_multi_qubit_operation: Preserves TOFFOLI gates without decomposition

Operations wrapped in TaggedOperation or CircuitOperation are properly unwrapped before validation to ensure correct gate type checking.

Benefits

Eliminates try-except control flow for gate validation
Leverages Cirq's optimized compilation pipeline
More maintainable and idiomatic code
Better performance through batch circuit transformation

Testing

All existing tests pass, including:

Single, double, and triple qubit gate tests
Rotation gate tests
Measurement and conditional operation tests
Circuit conversion tests

…supported_gates in our passes.py file in cirq

…our preprocessing

…irq's newer API no longer includes it, so we compute and attach it here

….py files for cirq

…ledGate instance

…r global phase differences

H gate and other supported gates were being unnecessarily decomposed (e.g., H -> Ry) because the decomposition method didn't properly check if gates were already in the target gateset. Fixed by unwrapping TaggedOperation wrappers and yielding supported gates unchanged.

Applied same unwrapping logic to _decompose_two_qubit_operation to prevent unnecessary decomposition of CNOT, CZ, SWAP, and TOFFOLI gates.

TwoQubitCompilationTargetGateset's preprocess_transformers was decomposing TOFFOLI gates before custom decomposition methods could preserve them. Fixed by overriding preprocess_transformers to exclude operations already in the target gateset from expand_composite decomposition.

Skip optimize_for_target_gateset for circuits containing ClassicallyControlledOperation to avoid unitary merge errors.

…t_gateset()

codecov · 2025-10-25T16:57:42Z

Codecov Report

❌ Patch coverage is 96.00000% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
qbraid_qir/cirq/QIRTargetGateSet.py	96.42%	3 Missing ⚠️
qbraid_qir/cirq/passes.py	93.75%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

TheGupta2012 · 2025-10-28T09:37:38Z

Why is this removed from the suite?

because it relies entirely on the _decompose_unsupported_gates function in the former implementation of qbraid_qir.cirq.passes which is no longer present in the current implementation

Okay but I think the test should be implemented with the new functionality i.e. having a Cirq program which is containing a custom gate, and then converted to QIR with the new decomposition function that you have developed. This test should validate the conversion for a non-native gate which "can" be decomposed with Cirq internal methods.

I have added tests for that

TheGupta2012 · 2025-10-28T09:38:46Z

Hi @feelerx , thank you for fixing this pending issue. Gave a couple of comments but the overall structure looks good! Can you also fix the formatting and bump coverage?

…ed_two_qubit_set, _supported_multi_qubit_set direct attributes of the QIRTargetGateSet class

… gateset 2. The preprocessed circuit is functionally equivalent to the original

TheGupta2012 · 2025-10-31T21:29:55Z

Hi @feelerx , thank you for the changes! I think their are still some linting issues in the format check. Could you please update that so that we can merge? Changes look good mostly

feelerx · 2025-11-01T17:57:02Z

I genuinely have no idea why there are still linting issues in the format check. Generates no error on my end and even has a 10/10 score here too

TheGupta2012 · 2025-11-01T22:56:38Z

Could you validate that the version of black, isort and pylint matches the one used in CI? I've encountered this issue sometimes where the version mismatch caused test failures.

feelerx · 2025-11-02T00:39:32Z

Could you validate that the version of black, isort and pylint matches the one used in CI? I've encountered this issue sometimes where the version mismatch caused test failures.

Could you please confirm which versions of black, isort, and pylint are being used in CI?

TheGupta2012 · 2025-11-03T16:48:47Z

@feelerx apparently one of the test file which you added did not have a qbraid header. Fixed it now, and thanks a ton for the work! Can you finally add the CHANGELOG entry for the change?

TheGupta2012 · 2025-11-23T14:00:20Z

Hi @feelerx , apologies for the delay in response but I think the coverage for this PR is still < the target (main). Can you please bump it to at least 94% for us to merge the code?

You can either -

Take a look at the uncovered lines on codecov
Generate the coverage locally using the command pytest --cov=qbraid_qir tests/ --cov-report=html and opening the coverage using open htmlcov/class_index.html (all assume the root dir of qbraid-qir)

…Set and passes in the cirq module

feelerx · 2025-11-28T23:33:23Z

open htmlcov/class_index.html

I have added more comprehensive tests for the files I updated (QIRTargetGateSet.py and passes.py for the cirq module).
The current coverage report is 93% when I run this pytest --cov=qbraid_qir tests/ --cov-report=html and open htmlcov/class_index.html
But the coverage for the two aforementioned files I primarily worked on are 96% and 95%, respectively.

feelerx added 14 commits October 24, 2025 06:09

commented out these tests as we are no longer using the _decompose_un…

252d210

…supported_gates in our passes.py file in cirq

we now use cirq.optimize_for_target_gateset and QIRTargetGateSet for …

2e19f53

…our preprocessing

The visitor later expects rotation gates to have a field (radians). C…

77e4fb4

…irq's newer API no longer includes it, so we compute and attach it here

we are no longer using the _decompose_unsupported_gates in our passes…

2108d7f

….py files for cirq

multiqubit measurement now supported, no longer raises error

8a75e05

XPowGate(exponent=0.25).controlled() now returns a valid cirq.Control…

660b40d

…ledGate instance

Fix qubit conversion tests to compare correct fixtures and account fo…

0924995

…r global phase differences

fix: preserve supported two-qubit gates from decomposition

b7bd238

Applied same unwrapping logic to _decompose_two_qubit_operation to prevent unnecessary decomposition of CNOT, CZ, SWAP, and TOFFOLI gates.

fix: bypass optimization for conditional operations

de05ce5

Skip optimize_for_target_gateset for circuits containing ClassicallyControlledOperation to avoid unitary merge errors.

final version of passes.py file using optimize_for_target_gateset()

6fdadcb

file containing QIRTargetGateSet class required by optimize_for_targe…

203d4d5

…t_gateset()

formatting clean up

0028a63

ryanhill1 requested a review from TheGupta2012 October 25, 2025 16:55

TheGupta2012 reviewed Oct 28, 2025

View reviewed changes

Comment thread qbraid_qir/cirq/QIRTargetGateSet.py Outdated

TheGupta2012 reviewed Oct 28, 2025

View reviewed changes

feelerx added 3 commits October 28, 2025 19:06

made _supported_single_qubit_set, _supported_power_gate_set, _support…

0d35bee

…ed_two_qubit_set, _supported_multi_qubit_set direct attributes of the QIRTargetGateSet class

tests that verify that 1. Custom gates are decomposed into the target…

10f5d83

… gateset 2. The preprocessed circuit is functionally equivalent to the original

formatting clean up

a2cb540

feelerx added 3 commits November 1, 2025 04:01

trying to fix pylint formatting issues

a84096e

formatting issues fixed completely I believe

f51f6bc

disable=unused-argument

2bb9c07

ran black qbraid_qir tests, affected the QIRTargetGateSet.py file

7b659aa

add header for test

4dbdfcd

added contribution of pull 248 to CHANGELOG.md

084f642

added tests to comprehensively cover full scope of both QIRTargetGate…

2bd519e

…Set and passes in the cirq module

TheGupta2012 merged commit 7b19222 into qBraid:main Nov 29, 2025
7 checks passed

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feelerx commented Oct 25, 2025

Refactor circuit preprocessing to use Cirq's optimize_for_target_gateset

Summary

Changes

Core Implementation

Key Features

Implementation Details

Benefits

Testing

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Refactor circuit preprocessing to use Cirq's `optimize_for_target_gateset`

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