Move optimizers/two_qubit_state_preparation.py to transformers/analytical_decompositions/two_qubit_state_preparation.py (quantumlib#4762)

Part of quantumlib#4722

This is safe to do without going through a deprecation cycle because `optimizers/two_qubit_state_preparation.py ` was recently introduced (quantumlib#4707) in the current dev version and hasn't been released yet.

Author: tanujkhattar

cirq-core/cirq/__init__.py

@@ -345,8 +345,6 @@
     MergeInteractions,
     MergeInteractionsToSqrtIswap,
     MergeSingleQubitGates,
-    prepare_two_qubit_state_using_cz,
-    prepare_two_qubit_state_using_sqrt_iswap,
     single_qubit_matrix_to_gates,
     single_qubit_matrix_to_pauli_rotations,
     single_qubit_matrix_to_phased_x_z,
@@ -366,6 +364,8 @@
     map_operations_and_unroll,
     merge_moments,
     merge_operations,
+    prepare_two_qubit_state_using_cz,
+    prepare_two_qubit_state_using_sqrt_iswap,
     unroll_circuit_op,
     unroll_circuit_op_greedy_earliest,
     unroll_circuit_op_greedy_frontier,

cirq-core/cirq/optimizers/__init__.py

@@ -72,11 +72,6 @@
     MergeSingleQubitGates,
 )
 
-from cirq.optimizers.two_qubit_state_preparation import (
-    prepare_two_qubit_state_using_cz,
-    prepare_two_qubit_state_using_sqrt_iswap,
-)
-
 from cirq.optimizers.decompositions import (
     is_negligible_turn,
     single_qubit_matrix_to_gates,

cirq-core/cirq/transformers/__init__.py

@@ -14,6 +14,11 @@
 
 """Circuit transformation utilities."""
 
+from cirq.transformers.analytical_decompositions import (
+    prepare_two_qubit_state_using_cz,
+    prepare_two_qubit_state_using_sqrt_iswap,
+)
+
 from cirq.transformers.transformer_primitives import (
     map_moments,
     map_operations,

cirq-core/cirq/transformers/analytical_decompositions/__init__.py

@@ -0,0 +1,20 @@
+# Copyright 2021 The Cirq Developers
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for analytical decomposition of cirq gates."""
+
+from cirq.transformers.analytical_decompositions.two_qubit_state_preparation import (
+    prepare_two_qubit_state_using_cz,
+    prepare_two_qubit_state_using_sqrt_iswap,
+)