From 497d5a4c3f6df0ae3392b13034066821380525a8 Mon Sep 17 00:00:00 2001
From: "mergify[bot]" <37929162+mergify[bot]@users.noreply.github.com>
Date: Tue, 4 May 2021 23:22:46 +0000
Subject: [PATCH] BasisTranslator skips translating gates already in target
 basis (#6350) (#6356)

* skip translating gates in target basis

* Update releasenotes/notes/bugfix-skip-target-basis-translation-12a9fa02c9ceef25.yaml

* fix lint issue

Co-authored-by: Matthew Treinish <mtreinish@kortar.org>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
(cherry picked from commit 8aceb73958566c1b59e47c51ebf38c8ea7321351)

Co-authored-by: Abdullah Ash- Saki <44783187+ashsaki@users.noreply.github.com>
---
 qiskit/transpiler/passes/basis/basis_translator.py           | 3 +++
 ...ugfix-skip-target-basis-translation-12a9fa02c9ceef25.yaml | 5 +++++
 2 files changed, 8 insertions(+)
 create mode 100644 releasenotes/notes/bugfix-skip-target-basis-translation-12a9fa02c9ceef25.yaml

diff --git a/qiskit/transpiler/passes/basis/basis_translator.py b/qiskit/transpiler/passes/basis/basis_translator.py
index df329165e61b..7dbea4dee2e0 100644
--- a/qiskit/transpiler/passes/basis/basis_translator.py
+++ b/qiskit/transpiler/passes/basis/basis_translator.py
@@ -269,6 +269,9 @@ def _basis_search(equiv_lib, source_basis, target_basis, heuristic):
         closed_set.add(current_basis)
 
         for gate_name, gate_num_qubits in current_basis:
+            if gate_name in target_basis:
+                continue
+
             equivs = equiv_lib._get_equivalences((gate_name, gate_num_qubits))
 
             basis_remain = current_basis - {(gate_name, gate_num_qubits)}
diff --git a/releasenotes/notes/bugfix-skip-target-basis-translation-12a9fa02c9ceef25.yaml b/releasenotes/notes/bugfix-skip-target-basis-translation-12a9fa02c9ceef25.yaml
new file mode 100644
index 000000000000..c139b7919036
--- /dev/null
+++ b/releasenotes/notes/bugfix-skip-target-basis-translation-12a9fa02c9ceef25.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixed an issue with :class:`~qiskit.transpiler.passes.BasisTranslator` where in some
+    cases it would translate gates already in the target basis.