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 <[email protected]> Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> (cherry picked from commit 8aceb73) Co-authored-by: Abdullah Ash- Saki <[email protected]>
Qiskit · May 4, 2021 · 497d5a4 · 497d5a4
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diff --git 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
@@ -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.