move qsd from qiskit/quantum_info/synthesis to qiskit/synthesis/unitary

qiskit/circuit/library/generalized_gates/unitary.py

@@ -146,7 +146,7 @@ def _define(self):
         elif self.num_qubits == 2:
             self.definition = two_qubit_cnot_decompose(self.to_matrix())
         else:
-            from qiskit.quantum_info.synthesis.qsd import (  # pylint: disable=cyclic-import
+            from qiskit.synthesis.unitary.qsd import (  # pylint: disable=cyclic-import
                 qs_decomposition,
             )
 

qiskit/synthesis/__init__.py

@@ -89,6 +89,10 @@
 
 .. autofunction:: synth_qft_line
 
+Unitary Synthesis
+=================
+
+.. autofunction:: qs_decomposition
 """
 
 from .evolution import (
@@ -126,3 +130,4 @@
 from .stabilizer import synth_stabilizer_layers, synth_stabilizer_depth_lnn
 from .discrete_basis import SolovayKitaevDecomposition, generate_basic_approximations
 from .qft import synth_qft_line
+from .unitary.qsd import qs_decomposition

qiskit/synthesis/unitary/__init__.py

@@ -0,0 +1,13 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2017 - 2023.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Module containing unitary synthesis methods."""

qiskit/transpiler/passes/synthesis/unitary_synthesis.py

@@ -866,7 +866,7 @@ def run(self, unitary, **options):
                 default=None,
             )
         else:
-            from qiskit.quantum_info.synthesis.qsd import (  # pylint: disable=cyclic-import
+            from qiskit.synthesis.unitary.qsd import (  # pylint: disable=cyclic-import
                 qs_decomposition,
             )
 

test/python/synthesis/test_synthesis.py

@@ -78,7 +78,7 @@
 )
 
 from qiskit.circuit.library.standard_gates.equivalence_library import _cnot_rxx_decompose
-from qiskit.quantum_info.synthesis import qsd
+from qiskit.synthesis.unitary import qsd
 from qiskit.test import QiskitTestCase