Catalyst support for qml.CosineWindow

[willjmax]

Compiling a circuit with QJIT that begins with a CosineWindow state preparation results in a compiler error. This is because Catalyst has optimizations for when the first operation is a state preparation, but these optimizations are not supported for CosineWindow. A workaround is to only perform the state preparation optimizations on the StatePrep and BasisState classes, rather than the more general StatePrepBase class.

This workaround requires additional changes to PennyLane (PR #6318) and PennyLane lightning (PR #929).

[dime10]

Thanks for the fix @willjmax! 🎉 Just some formatting changes below, but we should also make sure to add a test to confirm the template is working (e.g. in catalyst/frontend/test/pytest/test_templates.py).

[dime10]

Please make sure to also update the LIGHTNING_GIT_TAG variable as described in this comment :)

[willjmax]

Could you provide some more details on this? This is my first Catalyst contribution and I'm not sure I understand the comment 😕

[dime10]

Unfortunately, the process to update the dependency requires setting the version in a few places at the moment (this will become easier some time this quarter), the .dep-versions file you already noticed, and

• catalyst/doc/requirements.txt

  Lines 33 to 35 in 934726f

  	pennylane-lightning-kokkos==0.38.0
  	pennylane-lightning==0.38.0
  	pennylane==0.39.0.dev16

• catalyst/runtime/Makefile

  Line 17 in 934726f

  LIGHTNING_GIT_TAG_VALUE?=latest_release

• catalyst/.github/workflows/build-wheel-linux-x86_64.yaml

  Line 345 in 934726f

  -DLIGHTNING_GIT_TAG=latest_release \

  (and the other 3 wheel actions, although linux arm is special, see next item)

• catalyst/.github/workflows/scripts/linux_arm64/rh8/build_catalyst.sh

  Line 48 in 934726f

  -DLIGHTNING_GIT_TAG=latest_release \

There are two kinds of dependencies, "version strings" which can be used by pip when installing packages, and git refs which can be used by git when cloning repositories. For lightning because we currently build the lightning qubit device in the runtime, we have to make sure the git commit we use for this is the same as the lightning python package that will be installed by pip. To match the two take a particular PR that you want to depend on, say PennyLaneAI/pennylane-lightning#929. In the PR we see the package version string assigned to it:
PennyLaneAI/pennylane-lightning@02140db
Once the PR is merged, you will be able to see the merge commit on main and get its hash. Use this as the LIGHTNING_GIT_TAG.

[dime10]

For pennylane the idea is the same, although you don't need to worry about the git tag. Wait until the pennylane PR is merged, then get the package version that contains the PR you want. PennyLane updates its version and pushes a development package to pypi every night (contrary to lightning which does it every PR).
If you want the released dev package quicker, you can also trigger the action manually.

[dime10]

Lastly, you'll need a changelog entry, you can put your change in the improvements section:

catalyst/doc/releases/changelog-dev.md

Line 150 in 934726f

<h3>Improvements</h3>

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.93%. Comparing base (d4236ac) to head (c3afe75).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1166   +/-   ##
=======================================
  Coverage   97.93%   97.93%           
=======================================
  Files          77       77           
  Lines       10921    10921           
  Branches      971      971           
=======================================
  Hits        10695    10695           
  Misses        179      179           
  Partials       47       47           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.