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'Peephole' optimization - or: collecting and optimizing two-qubit blocks - before routing (backport #12727) #12881

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merged 1 commit into from
Aug 1, 2024

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Summary

Fixes #12562

Details and comments

This PR collects and consolidates two-qubit gates into blocks before routing. Each block is then subsequently analysed to determine whether the two-qubit unitary representing the block equals the identity or is a product of single-qubit gates. In the former case, the gates in the block are removed and in the latter case the block is replaced by single-qubit gates correspondingly.

Points up for debate:

  • Do we want to run the new pass Split2QUnitaries as part of ConsolidatedBlocks?
  • Do the passes for gate direction checks and fixes always play nicely with having two-qubit unitaries before routing? There were no test failures but I'm still wondering.
  • Is the current path of checking for the two-qubit unitaries for being a product of single-qubit unitaries the fastest or should we rely on Weyl-decomposition? If the former is true, we should probably port the corresponding functions to rust as they will touch a lot of two-qubit unitaries. :-)

This is an automatic backport of pull request #12727 done by [Mergify](https://mergify.com).

…cks - before routing (#12727)

* init

* up

* up

* Update builtin_plugins.py

* Update builtin_plugins.py

* reno

* Update builtin_plugins.py

* Update builtin_plugins.py

* Update peephole-before-routing-c3d184b740bb7a8b.yaml

* neko check

* check neko

* Update builtin_plugins.py

* test neko

* Update builtin_plugins.py

* Update builtin_plugins.py

* Update builtin_plugins.py

* lint

* tests and format

* remove FakeTorino test

* Update peephole-before-routing-c3d184b740bb7a8b.yaml

* Apply suggestions from code review

Co-authored-by: Matthew Treinish <[email protected]>

* comments from code review

* fix precision

* up

* up

* update

* up

* .

* cyclic import

* cycl import

* cyl import

* .

* circular import

* .

* lint

* Include new pass in docs

* Fix Split2QUnitaries dag manipulation

This commit fixes the dag handling to do the 1q unitary insertion.
Previously the dag manipulation was being done manually using the
insert_node_on_in_edges() rustworkx method. However as the original node
had 2 incoming edges for each qubit this caused the dag after running
the pass to become corrupted. Each of the new 1q unitary nodes would end
up with 2 incident edges and they would be in a sequence. This would result
in later passes not being able to correctly understand the state of the
circuit correctly. This was causing the unit tests to fail. This commit
fixes this by just using `substitute_node_with_dag()` to handle the
node substition, while doing it manually to avoid the overhead of
checking is probably possible, the case where a unitary is the product
of two 1q gates is not very common so optimizing it isn't super
critical.

* Update releasenotes/notes/peephole-before-routing-c3d184b740bb7a8b.yaml

* stricter check for doing split2q

* Update qiskit/transpiler/preset_passmanagers/builtin_plugins.py

Co-authored-by: Matthew Treinish <[email protected]>

* code review

* Update qiskit/transpiler/passes/optimization/split_2q_unitaries.py

Co-authored-by: Matthew Treinish <[email protected]>

* new tests

* typo

* lint

* lint

---------

Co-authored-by: Matthew Treinish <[email protected]>
(cherry picked from commit 1214d51)
@mergify mergify bot requested a review from a team as a code owner August 1, 2024 14:34
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@github-actions github-actions bot added Changelog: New Feature Include in the "Added" section of the changelog mod: transpiler Issues and PRs related to Transpiler labels Aug 1, 2024
@github-actions github-actions bot added this to the 1.2.0 milestone Aug 1, 2024
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Pull Request Test Coverage Report for Build 10200362536

Details

  • 59 of 62 (95.16%) changed or added relevant lines in 4 files are covered.
  • 14 unchanged lines in 2 files lost coverage.
  • Overall coverage increased (+0.008%) to 89.953%

Changes Missing Coverage Covered Lines Changed/Added Lines %
qiskit/transpiler/preset_passmanagers/builtin_plugins.py 28 29 96.55%
qiskit/transpiler/passes/optimization/split_2q_unitaries.py 29 31 93.55%
Files with Coverage Reduction New Missed Lines %
crates/qasm2/src/lex.rs 2 92.73%
crates/qasm2/src/parse.rs 12 97.15%
Totals Coverage Status
Change from base Build 10199425044: 0.008%
Covered Lines: 66738
Relevant Lines: 74192

💛 - Coveralls

@mtreinish mtreinish added this pull request to the merge queue Aug 1, 2024
Merged via the queue into stable/1.2 with commit f4cb741 Aug 1, 2024
18 checks passed
@mergify mergify bot deleted the mergify/bp/stable/1.2/pr-12727 branch August 1, 2024 16:36
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