From 743739b1eea3984394f0a1e58268f331bb517cb0 Mon Sep 17 00:00:00 2001
From: "Kevin J. Sung" <kevjsung@umich.edu>
Date: Fri, 17 May 2024 16:49:16 -0400
Subject: [PATCH] add insert_barrier argument to UnitaryOverlap (#12321)

* add insert_barrier argument to UnitaryOverlap

* set fold=-1 in circuit drawing
---
 qiskit/circuit/library/overlap.py           | 10 +++++++++-
 test/python/circuit/library/test_overlap.py | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/qiskit/circuit/library/overlap.py b/qiskit/circuit/library/overlap.py
index 38f5fb9184e1..2db6a80eedcc 100644
--- a/qiskit/circuit/library/overlap.py
+++ b/qiskit/circuit/library/overlap.py
@@ -59,7 +59,12 @@ class UnitaryOverlap(QuantumCircuit):
     """
 
     def __init__(
-        self, unitary1: QuantumCircuit, unitary2: QuantumCircuit, prefix1="p1", prefix2="p2"
+        self,
+        unitary1: QuantumCircuit,
+        unitary2: QuantumCircuit,
+        prefix1: str = "p1",
+        prefix2: str = "p2",
+        insert_barrier: bool = False,
     ):
         """
         Args:
@@ -69,6 +74,7 @@ def __init__(
                 if it is parameterized. Defaults to ``"p1"``.
             prefix2: The name of the parameter vector associated to ``unitary2``,
                 if it is parameterized. Defaults to ``"p2"``.
+            insert_barrier: Whether to insert a barrier between the two unitaries.
 
         Raises:
             CircuitError: Number of qubits in ``unitary1`` and ``unitary2`` does not match.
@@ -95,6 +101,8 @@ def __init__(
         # Generate the actual overlap circuit
         super().__init__(unitaries[0].num_qubits, name="UnitaryOverlap")
         self.compose(unitaries[0], inplace=True)
+        if insert_barrier:
+            self.barrier()
         self.compose(unitaries[1].inverse(), inplace=True)
 
 
diff --git a/test/python/circuit/library/test_overlap.py b/test/python/circuit/library/test_overlap.py
index a603f28037b1..1a95e3ba9155 100644
--- a/test/python/circuit/library/test_overlap.py
+++ b/test/python/circuit/library/test_overlap.py
@@ -131,6 +131,21 @@ def test_mismatching_qubits(self):
         with self.assertRaises(CircuitError):
             _ = UnitaryOverlap(unitary1, unitary2)
 
+    def test_insert_barrier(self):
+        """Test inserting barrier between circuits"""
+        unitary1 = EfficientSU2(1, reps=1)
+        unitary2 = EfficientSU2(1, reps=1)
+        overlap = UnitaryOverlap(unitary1, unitary2, insert_barrier=True)
+        self.assertEqual(overlap.count_ops()["barrier"], 1)
+        self.assertEqual(
+            str(overlap.draw(fold=-1, output="text")).strip(),
+            """
+   ┌───────────────────────────────────────┐ ░ ┌──────────────────────────────────────────┐
+q: ┤ EfficientSU2(p1[0],p1[1],p1[2],p1[3]) ├─░─┤ EfficientSU2_dg(p2[0],p2[1],p2[2],p2[3]) ├
+   └───────────────────────────────────────┘ ░ └──────────────────────────────────────────┘
+""".strip(),
+        )
+
 
 if __name__ == "__main__":
     unittest.main()