Add corresponding serialization for TwoPulseFSimTag

cirq-google/cirq_google/api/v2/program.proto

@@ -215,10 +215,18 @@ message FSimGate {
   FloatArg theta = 1;
   FloatArg phi = 2;
 
-  // If true, this is equivalent to:
-  // cirq.FSimGate(...).with_tags(cirq_google.FSimViaModelTag()).
+
   // This field controls how we translate the gate implementation.
-  bool translate_via_model = 3;
+  oneof translate_tag {
+    // If true, this is equivalent to:
+    // cirq.FSimGate(...).with_tags(cirq_google.FSimViaModelTag()).
+    bool translate_via_model = 3;
+
+    // If true, this is equivalent to:
+    // cirq.FSimGate(...).with_tags(cirq_google.TwoPulseFSimTag()).
+    bool translate_to_two_pulse = 4;
+  }
+
 }
 
 // Representation of cirq.ISwapPowGate

cirq-google/cirq_google/serialization/circuit_serializer.py

@@ -37,6 +37,7 @@
     InternalTag,
     PhysicalZTag,
     SycamoreGate,
+    TwoPulseFSimTag,
     WaitGateWithUnit,
     WillowGate,
 )
@@ -367,8 +368,16 @@ def _serialize_gate_op(
         elif isinstance(gate, cirq.FSimGate):
             arg_func_langs.float_arg_to_proto(gate.theta, out=msg.fsimgate.theta)
             arg_func_langs.float_arg_to_proto(gate.phi, out=msg.fsimgate.phi)
-            if any(isinstance(tag, FSimViaModelTag) for tag in op.tags):
+            has_model_tag = any(isinstance(tag, FSimViaModelTag) for tag in op.tags)
+            has_two_pulse_tag = any(isinstance(tag, TwoPulseFSimTag) for tag in op.tags)
+            if has_model_tag and has_two_pulse_tag:
+                raise ValueError(
+                    'FSimViaModelTag and TwoPulseFSimTag cannot be added to the same FSim gate'
+                )
+            if has_model_tag:
                 msg.fsimgate.translate_via_model = True
+            if has_two_pulse_tag:
+                msg.fsimgate.translate_to_two_pulse = True
         elif isinstance(gate, cirq.MeasurementGate):
             arg_func_langs.arg_to_proto(gate.key, out=msg.measurementgate.key)
             if len(gate.invert_mask):
@@ -870,6 +879,8 @@ def _deserialize_gate_op(
                 raise ValueError('theta and phi must be specified for FSimGate')
             if operation_proto.fsimgate.translate_via_model:
                 op = op.with_tags(FSimViaModelTag())
+            if operation_proto.fsimgate.translate_to_two_pulse:
+                op = op.with_tags(TwoPulseFSimTag())
         elif which_gate_type == 'measurementgate':
             key = arg_func_langs.arg_from_proto(
                 operation_proto.measurementgate.key, required_arg_name=None
@@ -1117,6 +1128,8 @@ def _deserialize_tag(self, msg: v2.program_pb2.Tag):
             return PhysicalZTag()
         elif which == 'fsim_via_model':
             return FSimViaModelTag()
+        elif which == 'two_pulse_fsim':
+            return TwoPulseFSimTag()
         elif which == 'calibration_tag':
             return CalibrationTag.from_proto(msg)
         elif which == 'internal_tag':

cirq-google/cirq_google/serialization/circuit_serializer_test.py

@@ -271,6 +271,20 @@ def circuit_proto(json: dict, qubits: list[str]):
             }
         ),
     ),
+    (
+        cirq.FSimGate(theta=2, phi=1)(Q0, Q1).with_tags(cg.TwoPulseFSimTag()),
+        op_proto(
+            {
+                'fsimgate': {
+                    'theta': {'float_value': 2.0},
+                    'phi': {'float_value': 1.0},
+                    'translate_to_two_pulse': True,
+                },
+                'qubit_constant_index': [0, 1],
+                'tag_indices': [2],
+            }
+        ),
+    ),
     (
         cirq.WaitGate(duration=cirq.Duration(nanos=15))(Q0),
         op_proto(
@@ -982,6 +996,13 @@ def test_deserialize_fsim_missing_parameters():
         serializer.deserialize(proto)
 
 
+def test_fsim_with_both_tags_raises_error():
+    serializer = cg.CircuitSerializer()
+    op = cirq.FSimGate(theta=2, phi=1)(Q0, Q1).with_tags(cg.FSimViaModelTag(), cg.TwoPulseFSimTag())
+    with pytest.raises(ValueError, match='FSimViaModelTag and TwoPulseFSimTag'):
+        serializer.serialize(cirq.Circuit(op))
+
+
 def test_deserialize_wrong_types():
     serializer = cg.CircuitSerializer()
     proto = circuit_proto(
@@ -1054,6 +1075,7 @@ def test_circuit_with_analog_detune_coupler_only():
     [
         cg.ops.DynamicalDecouplingTag('X'),
         cg.FSimViaModelTag(),
+        cg.TwoPulseFSimTag(),
         cg.PhysicalZTag(),
         cg.InternalTag(name='abc', package='xyz'),
     ],