Fixed a bug where nonequal boxes were considered equal (#14716) (#14722)

* Fixed a bug where nonequal boxes were considered equal

* Release note

* Update releasenotes/notes/fix-box-eq-check-1ff339fcc1db983f.yaml

* Update releasenotes/notes/fix-box-eq-check-1ff339fcc1db983f.yaml

---------


(cherry picked from commit 925f144)

Co-authored-by: gadial <[email protected]>
Co-authored-by: Matthew Treinish <[email protected]>

Author: 3 people

qiskit/dagcircuit/dagnode.py

@@ -174,6 +174,7 @@ def _for_loop_eq(node1, node2, bit_indices1, bit_indices2):
 def _box_eq(node1, node2, bit_indices1, bit_indices2):
     return (
         (node1.op.duration == node2.op.duration)
+        and (node1.op.unit == node2.op.unit)
         and (
             _circuit_to_dag(node1.op.blocks[0], node1.qargs, node1.cargs, bit_indices1)
             == _circuit_to_dag(node2.op.blocks[0], node2.qargs, node2.cargs, bit_indices2)

releasenotes/notes/fix-box-eq-check-1ff339fcc1db983f.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixed a bug in the :class:`.DAGOpNode` equality check, where comparing two :class:`.DAGOpNode`
+    objects that contain a :class:`.BoxOp` instruction. Previously, the :attr:`.BoxOp.unit` attribute was not
+    considered as part of the equality check which could lead to a two unequal nodes be evaluated as
+    equal.

test/python/dagcircuit/test_dagcircuit.py

@@ -45,6 +45,7 @@
     WhileLoopOp,
     CASE_DEFAULT,
     Store,
+    BoxOp,
 )
 from qiskit.circuit.classical import expr, types
 from qiskit.circuit.library import (
@@ -1734,6 +1735,34 @@ def test_unitary_gate_variants_eq(self):
 
         self.assertEqual(node1, node2)
 
+    def test_boxop_neq(self):
+        """Test non equality of nonequal DAGOpNodes and QuantumCircuits containing BoxOp gates."""
+        qc = QuantumCircuit()
+
+        box1 = BoxOp(body=qc, duration=300.0, unit="dt")
+        box2 = BoxOp(body=qc, duration=300.0, unit="ms")
+        node1 = DAGOpNode(op=box1, qargs=(), cargs=())
+        node2 = DAGOpNode(op=box2, qargs=(), cargs=())
+        self.assertNotEqual(node1, node2)
+
+        qc1 = QuantumCircuit()
+        qc2 = QuantumCircuit()
+        qc1.append(box1)
+        qc2.append(box2)
+        self.assertNotEqual(qc1, qc2)
+
+        box1 = BoxOp(body=qc, duration=300.0, unit="dt")
+        box2 = BoxOp(body=qc, duration=200.0, unit="dt")
+        node1 = DAGOpNode(op=box1, qargs=(), cargs=())
+        node2 = DAGOpNode(op=box2, qargs=(), cargs=())
+        self.assertNotEqual(node1, node2)
+
+        qc1 = QuantumCircuit()
+        qc2 = QuantumCircuit()
+        qc1.append(box1)
+        qc2.append(box2)
+        self.assertNotEqual(qc1, qc2)
+
     def test_dag_eq(self):
         """DAG equivalence check: True."""
         #        ┌───┐                ┌───┐