Add json serialization for PauliInteractionGate

cirq-core/cirq/json_resolver_cache.py

@@ -143,6 +143,7 @@ def _symmetricalqidpair(qids):
         'ParamResolver': cirq.ParamResolver,
         'ParallelGate': cirq.ParallelGate,
         'ParallelGateFamily': cirq.ParallelGateFamily,
+        'PauliInteractionGate': cirq.PauliInteractionGate,
         'PauliMeasurementGate': cirq.PauliMeasurementGate,
         'PauliString': cirq.PauliString,
         'PauliStringPhasor': cirq.PauliStringPhasor,

cirq-core/cirq/ops/gate_operation_test.py

@@ -505,7 +505,6 @@ def all_subclasses(cls):
         cirq.interop.quirk.QuirkArithmeticGate,
         # No reason given for missing json.
         # TODO(#5353): Serialize these gates.
-        cirq.PauliInteractionGate,
         cirq.ArithmeticGate,
     }
 

cirq-core/cirq/ops/pauli_interaction_gate.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import List, Sequence, Tuple, cast, Dict, TYPE_CHECKING
+from typing import Any, Dict, List, Sequence, TYPE_CHECKING, Tuple
 
 import numpy as np
 
@@ -24,17 +24,11 @@
 if TYPE_CHECKING:
     import cirq
 
-pauli_eigen_map = cast(
-    Dict[pauli_gates.Pauli, np.ndarray],
-    {
-        pauli_gates.X: (np.array([[0.5, 0.5], [0.5, 0.5]]), np.array([[0.5, -0.5], [-0.5, 0.5]])),
-        pauli_gates.Y: (
-            np.array([[0.5, -0.5j], [0.5j, 0.5]]),
-            np.array([[0.5, 0.5j], [-0.5j, 0.5]]),
-        ),
-        pauli_gates.Z: (np.diag([1, 0]), np.diag([0, 1])),
-    },
-)
+PAULI_EIGEN_MAP: Dict[pauli_gates.Pauli, np.ndarray] = {
+    pauli_gates.X: (np.array([[0.5, 0.5], [0.5, 0.5]]), np.array([[0.5, -0.5], [-0.5, 0.5]])),
+    pauli_gates.Y: (np.array([[0.5, -0.5j], [0.5j, 0.5]]), np.array([[0.5, 0.5j], [-0.5j, 0.5]])),
+    pauli_gates.Z: (np.diag([1, 0]), np.diag([0, 1])),
+}
 
 
 @value.value_equality
@@ -108,8 +102,8 @@ def _eigen_shifts(self) -> List[float]:
 
     def _eigen_components(self) -> List[Tuple[float, np.ndarray]]:
         comp1 = np.kron(
-            pauli_eigen_map[self.pauli0][not self.invert0],
-            pauli_eigen_map[self.pauli1][not self.invert1],
+            PAULI_EIGEN_MAP[self.pauli0][not self.invert0],
+            PAULI_EIGEN_MAP[self.pauli1][not self.invert1],
         )
         comp0 = np.eye(4) - comp1
         return [(0, comp0), (1, comp1)]
@@ -153,6 +147,9 @@ def __repr__(self) -> str:
             return base
         return f'({base}**{proper_repr(self._exponent)})'
 
+    def _json_dict_(self) -> Dict[str, Any]:
+        return protocols.obj_to_dict_helper(self, ["pauli0", "invert0", "pauli1", "invert1"])
+
 
 PauliInteractionGate.CZ = PauliInteractionGate(pauli_gates.Z, False, pauli_gates.Z, False)
 PauliInteractionGate.CNOT = PauliInteractionGate(pauli_gates.Z, False, pauli_gates.X, False)

cirq-core/cirq/protocols/json_test_data/PauliInteractionGate.json

@@ -0,0 +1,15 @@
+{
+  "cirq_type": "PauliInteractionGate",
+  "pauli0": {
+    "cirq_type": "_PauliZ",
+    "exponent": 1.0,
+    "global_shift": 0.0
+  },
+  "invert0": false,
+  "pauli1": {
+    "cirq_type": "_PauliX",
+    "exponent": 1.0,
+    "global_shift": 0.0
+  },
+  "invert1": true
+}

cirq-core/cirq/protocols/json_test_data/PauliInteractionGate.repr

@@ -0,0 +1 @@
+cirq.PauliInteractionGate(cirq.Z, False, cirq.X, True)

cirq-core/cirq/protocols/json_test_data/spec.py

@@ -45,7 +45,6 @@
         'Linspace',
         'ListSweep',
         'NeutralAtomDevice',
-        'PauliInteractionGate',
         'PauliSumCollector',
         'PauliSumExponential',
         'PauliTransform',