Fix LQ version checking out in LK-CPU tests (#723)

* Fix checkout LQ

* Auto update version from '0.37.0-dev6' to '0.37.0-dev7'

* Try Ali's suggestion.

* Auto update version from '0.37.0-dev7' to '0.37.0-dev8'

* Auto update version from '0.37.0-dev8' to '0.37.0-dev9'

* Update changelog.

* Fix string comp.

* Pin autoray<0.6.10

* Auto update version from '0.37.0-dev8' to '0.37.0-dev9'

* trigger ci

* trigger ci

* Use float to define gates.

* Revert.

* Auto update version from '0.37.0-dev9' to '0.37.0-dev10'

* Auto update version from '0.37.0-dev10' to '0.37.0-dev11'

* Fix quimb dep.

---------

Co-authored-by: ringo-but-quantum <github-ringo-but-quantum@xanadu.ai>
Co-authored-by: Ali Asadi <10773383+maliasadi@users.noreply.github.com>

.github/CHANGELOG.md

@@ -37,6 +37,9 @@
 
 ### Bug fixes
 
+* The `.github/workflows/tests_lkcpu_python.yml` workflow properly checks out the release or stable version of Lightning-Qubit during the test job.
+  [(#723)](https://github.com/PennyLaneAI/pennylane-lightning/pull/723)
+
 ### Contributors
 
 This release contains contributions from (in alphabetical order):

.github/workflows/tests_lkcpu_python.yml

@@ -168,6 +168,18 @@ jobs:
           fetch-tags: true
           path: main
 
+      - name: Switch to release build of Lightning
+        if: inputs.lightning-version == 'release'
+        run: |
+          cd main
+          git fetch --all
+          git checkout $(git branch -a --list "origin/v*rc*" | tail -1)
+
+      - name: Switch to stable build of Lightning
+        if: inputs.lightning-version == 'stable'
+        run: |
+          python -m pip install -U pennylane-lightning --no-deps
+
       - uses: actions/download-artifact@v4
         with:
           name: ${{ matrix.pl_backend }}-${{ matrix.exec_model }}_name.txt
@@ -185,7 +197,9 @@ jobs:
           cd main
           python -m pip install -r requirements-dev.txt
           python -m pip install openfermionpyscf
-          SKIP_COMPILATION=True python -m pip install . -vv
+          if [ '${{ inputs.lightning-version }}' != 'stable' ]; then
+            SKIP_COMPILATION=True python -m pip install . -vv
+          fi
           python -m pip install ${{ github.workspace }}/$WHEEL_NAME --no-deps
 
       - name: Checkout PennyLane for release build

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.37.0-dev10"
+__version__ = "0.37.0-dev11"

requirements-dev.txt

@@ -20,4 +20,4 @@ custatevec-cu12
 pylint
 scipy~=1.12.0
 autoray<0.6.10
-git+https://github.com/jcmgray/quimb.git
+quimb==1.8.1

tests/lightning_tensor/test_quimb_mps.py

@@ -198,7 +198,6 @@ def test_supported_observables_can_be_implemented(self, observable, backend, met
                 assert isinstance(result, (float, np.ndarray))
 
         else:
-
             tape = qml.tape.QuantumScript(
                 [qml.PauliX(0)],
                 [qml.expval(obs[observable])],