qsvt wire order (#6212)

The order of the wires is not correct. First we must take those of the projector --------- Co-authored-by: Austin Huang <[email protected]>
PennyLaneAI · Sep 5, 2024 · b37234d · b37234d
1 parent b47ef1c
commit b37234d
Show file tree

Hide file tree

Showing 3 changed files with 11 additions and 6 deletions.
diff --git a/doc/releases/changelog-dev.md b/doc/releases/changelog-dev.md
@@ -34,10 +34,14 @@
 * Fix `qml.PrepSelPrep` template to work with `torch`:
   [(#6191)](https://github.com/PennyLaneAI/pennylane/pull/6191)
 
-<h3>Contributors ✍️</h3>
+* The ``qml.QSVT`` template now orders the ``projector`` wires first and the ``UA`` wires second, which is the expected order of the decomposition.
+  [(#6212)](https://github.com/PennyLaneAI/pennylane/pull/6212)
+
+* <h3>Contributors ✍️</h3>
 
 This release contains contributions from (in alphabetical order):
 
+Guillermo Alonso
 Utkarsh Azad
 Jack Brown
 Christina Lee

diff --git a/pennylane/templates/subroutines/qsvt.py b/pennylane/templates/subroutines/qsvt.py
@@ -285,9 +285,9 @@ def __init__(self, UA, projectors, id=None):
             "projectors": projectors,
         }
 
-        total_wires = qml.wires.Wires(UA.wires) + qml.wires.Wires.all_wires(
+        total_wires = qml.wires.Wires.all_wires(
             [proj.wires for proj in projectors]
-        )
+        ) + qml.wires.Wires(UA.wires)
 
         super().__init__(wires=total_wires, id=id)
 

diff --git a/tests/templates/test_subroutines/test_qsvt.py b/tests/templates/test_subroutines/test_qsvt.py
@@ -172,9 +172,10 @@ def test_decomposition_queues_its_contents(self):
     def test_wire_order(self):
         """Test that the wire order is preserved."""
 
-        op = qml.QFT(wires=[2, 1])
-        qsvt_wires = qml.QSVT(op, [op]).wires
-        assert qsvt_wires == op.wires
+        op1 = qml.GroverOperator(wires=[0, 3])
+        op2 = qml.QFT(wires=[2, 1])
+        qsvt_wires = qml.QSVT(op2, [op1]).wires
+        assert qsvt_wires == op1.wires + op2.wires
 
     @pytest.mark.parametrize(
         ("quantum_function", "phi_func", "A", "phis", "results"),