✨ Add IQM move gate support and star-topology Qiskit compilation via resonator abstraction

[marcelwa]

Description

This PR finishes off the move gate support started in #1844: move circuits were already recognized in the target, but converting them to IQM JSON for job submission wasn't implemented yet, so actually submitting one just raised UnsupportedOperationError.

While at it, I pulled a couple of _build_target and run internals out into small overridable methods so IQM's star-topology backend can customize target construction and circuit preprocessing without having to duplicate the whole pipeline.

Part of this PR has been assisted by Claude Sonnet 5 in Claude Code.

Checklist

• The pull request only contains commits that are focused and relevant to this change.
• I have added appropriate tests that cover the new/changed functionality.
• I have updated the documentation to reflect these changes.
• I have added entries to the changelog for any noteworthy additions, changes, fixes, or removals.
• I have added migration instructions to the upgrade guide (if needed).
• The changes follow the project's style guidelines and introduce no new warnings.
• The changes are fully tested and pass the CI checks.
• I have reviewed my own code changes.

If PR contains AI-assisted content:

• I have disclosed the use of AI tools in the PR description as per our AI Usage Guidelines.
• AI-assisted commits include an Assisted-by: [Model Name] via [Tool Name] footer.
• I confirm that I have personally reviewed and understood all AI-generated content, and accept full responsibility for it.

[codecov]

Codecov Report

❌ Patch coverage is 92.00000% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
python/mqt/core/plugins/qiskit/backend.py	90.1%	6 Missing ⚠️

📢 Thoughts on this report? Let us know!

[marcelwa]

@coderabbitai full review

[coderabbitai]

✅ Action performed

Full review finished.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a MoveGate Qiskit gate class representing IQM's opaque 2-qubit move operation, exports it from the plugin package, and integrates it into IQM JSON conversion. QDMIBackend is refactored to extract operation-to-Target mapping logic into a helper method and add two overridable extension hooks: _target_num_qubits() and _preprocess_circuit().

Changes

MoveGate Feature and Backend Extension Seams

Layer / File(s)	Summary
MoveGate class definition and exports python/mqt/core/plugins/qiskit/gates.py, python/mqt/core/plugins/qiskit/__init__.py	New MoveGate(Gate) class representing a 2-qubit "move" opcode with __dir__() and __all__; exported conditionally from the plugin package.
QDMIBackend refactor and extension hooks python/mqt/core/plugins/qiskit/backend.py	Removes local MoveGate definition in favor of the imported class; extracts _add_operation_to_target() from _build_target(); adds overridable _target_num_qubits() and _preprocess_circuit() hooks, the latter called in run() after parameter binding.
IQM JSON conversion support python/mqt/core/plugins/qiskit/converters.py	qiskit_to_iqm_json now recognizes MoveGate and emits a "move" instruction with a two-qubit "locus" and empty args.
Tests and changelog test/python/plugins/qiskit/test_mock_backend.py, CHANGELOG.md	Adds tests verifying MoveGate exposure in the backend target and correct IQM JSON conversion; updates changelog with the new feature entry and PR link.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

• munich-quantum-toolkit/core#1375: Extends the same Qiskit→IQM JSON conversion pathway introduced there by adding MoveGate handling inside qiskit_to_iqm_json.
• munich-quantum-toolkit/core#1384: Both PRs modify QDMIBackend's device-operation-to-Target mapping/validation logic in backend.py.
• munich-quantum-toolkit/core#1385: Both PRs modify QDMIBackend.run()'s flow, with this PR adding _preprocess_circuit after the parameter binding logic introduced there.

Suggested labels: QDMI

Suggested reviewers: burgholzer

Poem

A rabbit hops with sites in tow,
from qubit here to qubit there we go,
the move gate whispers "star-shaped hop,"
through JSON locus, never stop.
🐇✨ hooks now bend to your design—
preprocess, target, all align!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly reflects the main change: IQM move gate support plus star-topology Qiskit compilation refactoring.
Description check	✅ Passed	The description includes the change summary, motivation, and context, and its checklist is mostly complete despite a few unchecked optional items.

✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch move-gate-and-star-topology-support

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@python/mqt/core/plugins/qiskit/backend.py`:
- Around line 259-356: _reduce complexity in _add_operation_to_target by
extracting the single- and two-qubit property population logic into a small
helper and restructuring early exits so the method has fewer return statements
and branches. Keep the behavior of _add_operation_to_target,
_get_operation_qargs, and target.add_instruction/update_instruction_properties
unchanged, but move the qargs/property update loops for one- and two-qubit
operations into a separate helper to make the override path readable and satisfy
PLR0911/PLR0912 without suppressing warnings._

In `@python/mqt/core/plugins/qiskit/converters.py`:
- Around line 125-137: The MOVE handling in converters.py duplicates the same
two-qubit locus lookup used by the CZ branch, so extract that shared logic into
a helper such as a two_qubit_locus function used by both the MoveGate and CZ
operation paths. Keep the operation-specific "name" value in each branch, but
reuse the helper for building the locus from circuit, qargs, and sites so future
empty-args two-qubit operations can share the same code path.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 86756e14-6d2e-4844-aeef-d2df2b90655a

📥 Commits

Reviewing files that changed from the base of the PR and between 26a0d98 and 1f18042.

⛔ Files ignored due to path filters (2)

• docs/fig-qpe-dark.svg is excluded by !**/*.svg
• docs/fig-qpe-light.svg is excluded by !**/*.svg

📒 Files selected for processing (6)

• CHANGELOG.md
• python/mqt/core/plugins/qiskit/__init__.py
• python/mqt/core/plugins/qiskit/backend.py
• python/mqt/core/plugins/qiskit/converters.py
• python/mqt/core/plugins/qiskit/gates.py
• test/python/plugins/qiskit/test_mock_backend.py