MLIR Conversion(s)

[flowerthrower]

Description

This PR originates from this mqt-mlir PR and introduces conversions between Catalysts quantum dialect and the MQTOpt dialect.

Checklist:

• The pull request only contains commits that are related to it.
• I have added appropriate tests and documentation.
• I have made sure that all CI jobs on GitHub pass.
• The pull request introduces no new warnings and follows the project's style guidelines.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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[burgholzer]

Now that #879 is merged, this needs to be rebased

[ystade]

We decided that we first merge the plugin (#881) and afterward integrate those changes here and then merge this PR.

This has the following advantages:

• Right now, to test the conversion passes of this PR, quantum-opt must be linked with a target from the Catalyst project, in particular the MLIRQuantum target containing the dialect. This is necessary even tough apart from testing there is no real use case for processing catalyst mlir without using the frontend Pennylane.
• Vice versa, the plugin does not need to be linked with any target of the Catalyst project, it only requires the header files that (hopefully) will be shipped with the pip wheel of catalyst sonn. Then this plugin can (and must) be invoked from pennylane and this way the conversion passes can be tested without requireing any target of catalyst. Only an easy install of catalyst in the python environment is necessary.

[flowerthrower]

The conversions implemented in this PR were moved to #881.