Split new code into a separate file

cirq-core/cirq/optimizers/__init__.py

@@ -58,6 +58,9 @@
 
 from cirq.optimizers.merge_interactions import (
     MergeInteractions,
+)
+
+from cirq.optimizers.merge_interactions_to_sqrt_iswap import (
     MergeInteractionsToSqrtIswap,
 )
 

cirq-core/cirq/optimizers/merge_interactions.py

@@ -20,7 +20,7 @@
 import numpy as np
 
 from cirq import circuits, ops, protocols
-from cirq.optimizers import two_qubit_decompositions, two_qubit_to_sqrt_iswap
+from cirq.optimizers import two_qubit_decompositions
 
 if TYPE_CHECKING:
     import cirq
@@ -237,52 +237,3 @@ def _two_qubit_matrix_to_operations(
         return two_qubit_decompositions.two_qubit_matrix_to_operations(
             q0, q1, mat, self.allow_partial_czs, self.tolerance, False
         )
-
-
-class MergeInteractionsToSqrtIswap(MergeInteractionsAbc):
-    """Combines series of adjacent one and two-qubit gates operating on a pair
-    of qubits and replaces each series with the minimum number of SQRT_ISWAP
-    gates."""
-
-    def __init__(
-        self,
-        tolerance: float = 1e-8,
-        require_three_sqrt_iswap: bool = False,
-        use_sqrt_iswap_inv: bool = False,
-        post_clean_up: Callable[[Sequence[ops.Operation]], ops.OP_TREE] = lambda op_list: op_list,
-    ) -> None:
-        super().__init__(tolerance=tolerance, post_clean_up=post_clean_up)
-        self.require_three_sqrt_iswap = require_three_sqrt_iswap
-        self.use_sqrt_iswap_inv = use_sqrt_iswap_inv
-
-    def _may_keep_old_op(self, old_op: 'cirq.Operation') -> bool:
-        """Returns True if the old two-qubit operation may be left unchanged
-        without decomposition."""
-        return isinstance(old_op.gate, ops.ISwapPowGate) and old_op.gate.exponent == 0.5
-
-    def _two_qubit_matrix_to_operations(
-        self,
-        q0: 'cirq.Qid',
-        q1: 'cirq.Qid',
-        mat: np.ndarray,
-    ) -> Sequence['cirq.Operation']:
-        """Decomposes the merged two-qubit gate unitary into the minimum number
-        of SQRT_ISWAP gates.
-
-        Args:
-            q0: The first qubit being operated on.
-            q1: The other qubit being operated on.
-            mat: Defines the operation to apply to the pair of qubits.
-
-        Returns:
-            A list of operations implementing the matrix.
-        """
-        return two_qubit_to_sqrt_iswap.two_qubit_matrix_to_sqrt_iswap_operations(
-            q0,
-            q1,
-            mat,
-            required_sqrt_iswap_count=3 if self.require_three_sqrt_iswap else None,
-            use_sqrt_iswap_inv=self.use_sqrt_iswap_inv,
-            atol=self.tolerance,
-            check_preconditions=False,
-        )

cirq-core/cirq/optimizers/merge_interactions_to_sqrt_iswap.py

@@ -0,0 +1,75 @@
+# Copyright 2018 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.
+
+"""An optimization pass that combines adjacent series of gates on two qubits and
+outputs a circuit with SQRT_ISWAP or SQRT_ISWAP_INV gates."""
+
+from typing import Callable, Sequence, TYPE_CHECKING
+
+import numpy as np
+
+from cirq import ops
+from cirq.optimizers import two_qubit_to_sqrt_iswap, merge_interactions
+
+if TYPE_CHECKING:
+    import cirq
+
+
+class MergeInteractionsToSqrtIswap(merge_interactions.MergeInteractionsAbc):
+    """Combines series of adjacent one and two-qubit gates operating on a pair
+    of qubits and replaces each series with the minimum number of SQRT_ISWAP
+    gates."""
+
+    def __init__(
+        self,
+        tolerance: float = 1e-8,
+        require_three_sqrt_iswap: bool = False,
+        use_sqrt_iswap_inv: bool = False,
+        post_clean_up: Callable[[Sequence[ops.Operation]], ops.OP_TREE] = lambda op_list: op_list,
+    ) -> None:
+        super().__init__(tolerance=tolerance, post_clean_up=post_clean_up)
+        self.require_three_sqrt_iswap = require_three_sqrt_iswap
+        self.use_sqrt_iswap_inv = use_sqrt_iswap_inv
+
+    def _may_keep_old_op(self, old_op: 'cirq.Operation') -> bool:
+        """Returns True if the old two-qubit operation may be left unchanged
+        without decomposition."""
+        return isinstance(old_op.gate, ops.ISwapPowGate) and old_op.gate.exponent == 0.5
+
+    def _two_qubit_matrix_to_operations(
+        self,
+        q0: 'cirq.Qid',
+        q1: 'cirq.Qid',
+        mat: np.ndarray,
+    ) -> Sequence['cirq.Operation']:
+        """Decomposes the merged two-qubit gate unitary into the minimum number
+        of SQRT_ISWAP gates.
+
+        Args:
+            q0: The first qubit being operated on.
+            q1: The other qubit being operated on.
+            mat: Defines the operation to apply to the pair of qubits.
+
+        Returns:
+            A list of operations implementing the matrix.
+        """
+        return two_qubit_to_sqrt_iswap.two_qubit_matrix_to_sqrt_iswap_operations(
+            q0,
+            q1,
+            mat,
+            required_sqrt_iswap_count=3 if self.require_three_sqrt_iswap else None,
+            use_sqrt_iswap_inv=self.use_sqrt_iswap_inv,
+            atol=self.tolerance,
+            check_preconditions=False,
+        )