Fixing bug QSVT wire order (PennyLaneAI#5959)

**Context:** The order of the wires in QSVT is not maintained as they are used as a set internally. **issue** Solves issue PennyLaneAI#5965 --------- Co-authored-by: soranjh <[email protected]>
QSAR-UBC · Jul 12, 2024 · f1b5e31 · f1b5e31
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diff --git a/doc/releases/changelog-dev.md b/doc/releases/changelog-dev.md
@@ -56,6 +56,9 @@
 
 <h3>Bug fixes 🐛</h3>
 
+* `qml.QSVT` is updated to store wire order correctly.
+  [(#5959)](https://github.com/PennyLaneAI/pennylane/pull/5959)
+
 * `qml.devices.qubit.measure_with_samples` now returns the correct result if the provided measurements
   contain sum of operators acting on the same wire.
   [(#5978)](https://github.com/PennyLaneAI/pennylane/pull/5978)
@@ -66,7 +69,7 @@
 <h3>Contributors ✍️</h3>
 
 This release contains contributions from (in alphabetical order):
-
+Guillermo Alonso,
 Ahmed Darwish,
 Astral Cai,
 Yushao Chen,

diff --git a/pennylane/templates/subroutines/qsvt.py b/pennylane/templates/subroutines/qsvt.py
@@ -285,10 +285,10 @@ def __init__(self, UA, projectors, id=None):
             "projectors": projectors,
         }
 
-        ua_wires = UA.wires.toset()
-        proj_wires = set.union(*(proj.wires.toset() for proj in projectors))
+        total_wires = qml.wires.Wires(UA.wires) + qml.wires.Wires.all_wires(
+            [proj.wires for proj in projectors]
+        )
 
-        total_wires = ua_wires.union(proj_wires)
         super().__init__(wires=total_wires, id=id)
 
     def map_wires(self, wire_map: dict):

diff --git a/tests/templates/test_subroutines/test_qsvt.py b/tests/templates/test_subroutines/test_qsvt.py
@@ -169,6 +169,13 @@ def test_decomposition_queues_its_contents(self):
         for op1, op2 in zip(ops, decomp):
             qml.assert_equal(op1, op2)
 
+    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
+
     @pytest.mark.parametrize(
         ("quantum_function", "phi_func", "A", "phis", "results"),
         [