Enable CircuitOp serialization. (#4344)

This PR adds `CircuitOperation` serializers to the default gateset used in QCS. After it is submitted, `CircuitOperation`s sent to QCS will be serialized in a compact format, reducing the size of highly-repetitive circuits.

Not included in this PR:
* Support for `CircuitOperation`s in `cirq.optimized_for_sycamore` (to be added in #4336)

cirq-google/cirq_google/devices/known_devices_test.py

@@ -102,6 +102,9 @@ def test_foxtail_device_proto():
     gate_duration_picos: 4000000
     valid_targets: "meas_targets"
   }
+  valid_gates {
+    id: "circuit"
+  }
 }
 valid_qubits: "0_0"
 valid_qubits: "0_1"
@@ -389,6 +392,9 @@ def test_multiple_gate_sets():
     gate_duration_picos: 14141
     valid_targets: "meas_targets"
   }
+  valid_gates {
+    id: "circuit"
+  }
 }
 valid_gate_sets {
   name: "half_pi_gateset"

cirq-google/cirq_google/gate_sets.py

@@ -33,6 +33,8 @@
     COUPLER_PULSE_DESERIALIZER,
     WAIT_GATE_SERIALIZER,
     WAIT_GATE_DESERIALIZER,
+    CIRCUIT_OP_SERIALIZER,
+    CIRCUIT_OP_DESERIALIZER,
 )
 
 SYC_GATESET = serializable_gate_set.SerializableGateSet(
@@ -43,13 +45,15 @@
         *SINGLE_QUBIT_HALF_PI_SERIALIZERS,
         MEASUREMENT_SERIALIZER,
         WAIT_GATE_SERIALIZER,
+        CIRCUIT_OP_SERIALIZER,
     ],
     deserializers=[
         SYC_DESERIALIZER,
         *SINGLE_QUBIT_DESERIALIZERS,
         *SINGLE_QUBIT_HALF_PI_DESERIALIZERS,
         MEASUREMENT_DESERIALIZER,
         WAIT_GATE_DESERIALIZER,
+        CIRCUIT_OP_DESERIALIZER,
     ],
 )
 document(SYC_GATESET, """Gate set with fsim(pi/2, pi/6) as the core 2 qubit interaction.""")
@@ -61,12 +65,14 @@
         *SINGLE_QUBIT_SERIALIZERS,
         MEASUREMENT_SERIALIZER,
         WAIT_GATE_SERIALIZER,
+        CIRCUIT_OP_SERIALIZER,
     ],
     deserializers=[
         *SQRT_ISWAP_DESERIALIZERS,
         *SINGLE_QUBIT_DESERIALIZERS,
         MEASUREMENT_DESERIALIZER,
         WAIT_GATE_DESERIALIZER,
+        CIRCUIT_OP_DESERIALIZER,
     ],
 )
 document(SQRT_ISWAP_GATESET, """Gate set with sqrt(iswap) as the core 2 qubit interaction.""")
@@ -79,12 +85,14 @@
         *SINGLE_QUBIT_SERIALIZERS,
         MEASUREMENT_SERIALIZER,
         WAIT_GATE_SERIALIZER,
+        CIRCUIT_OP_SERIALIZER,
     ],
     deserializers=[
         LIMITED_FSIM_DESERIALIZER,
         *SINGLE_QUBIT_DESERIALIZERS,
         MEASUREMENT_DESERIALIZER,
         WAIT_GATE_DESERIALIZER,
+        CIRCUIT_OP_DESERIALIZER,
     ],
 )
 document(FSIM_GATESET, """Gate set that combines sqrt(iswap) and syc as one fsim id.""")
@@ -98,13 +106,15 @@
         *SINGLE_QUBIT_SERIALIZERS,
         MEASUREMENT_SERIALIZER,
         WAIT_GATE_SERIALIZER,
+        CIRCUIT_OP_SERIALIZER,
     ],
     deserializers=[
         COUPLER_PULSE_DESERIALIZER,
         LIMITED_FSIM_DESERIALIZER,
         *SINGLE_QUBIT_DESERIALIZERS,
         MEASUREMENT_DESERIALIZER,
         WAIT_GATE_DESERIALIZER,
+        CIRCUIT_OP_DESERIALIZER,
     ],
 )
 document(
@@ -120,11 +130,13 @@
         *SINGLE_QUBIT_SERIALIZERS,
         CZ_POW_SERIALIZER,
         MEASUREMENT_SERIALIZER,
+        CIRCUIT_OP_SERIALIZER,
     ],
     deserializers=[
         *SINGLE_QUBIT_DESERIALIZERS,
         CZ_POW_DESERIALIZER,
         MEASUREMENT_DESERIALIZER,
+        CIRCUIT_OP_DESERIALIZER,
     ],
 )
 document(XMON, """Gate set for XMON devices.""")

cirq-google/cirq_google/gate_sets_test.py

@@ -527,3 +527,50 @@ def test_serialize_deserialize_wait_gate():
     assert cg.SYC_GATESET.deserialize_op(proto) == op
     assert cg.SQRT_ISWAP_GATESET.serialize_op(op) == proto
     assert cg.SQRT_ISWAP_GATESET.deserialize_op(proto) == op
+
+
+def default_circuit_proto():
+    op1 = v2.program_pb2.Operation()
+    op1.gate.id = 'x_pow'
+    op1.args['half_turns'].arg_value.string_value = 'k'
+    op1.qubits.add().id = '1_1'
+
+    return v2.program_pb2.Circuit(
+        scheduling_strategy=v2.program_pb2.Circuit.MOMENT_BY_MOMENT,
+        moments=[
+            v2.program_pb2.Moment(
+                operations=[op1],
+            ),
+        ],
+    )
+
+
+def default_circuit():
+    return cirq.FrozenCircuit(
+        cirq.X(cirq.GridQubit(1, 1)) ** sympy.Symbol('k'),
+        cirq.measure(cirq.GridQubit(1, 1), key='m'),
+    )
+
+
+@pytest.mark.parametrize('gateset', [cg.XMON, cg.SYC_GATESET, cg.SQRT_ISWAP_GATESET])
+def test_serialize_deserialize_circuit_op(gateset):
+    circuit_op = cirq.CircuitOperation(default_circuit())
+    proto = v2.program_pb2.CircuitOperation()
+    proto.circuit_constant_index = 0
+    proto.repetition_specification.repetition_count = 1
+
+    constants = [default_circuit_proto()]
+    raw_constants = {default_circuit(): 0}
+    assert (
+        gateset.serialize_op(circuit_op, constants=constants, raw_constants=raw_constants) == proto
+    )
+
+    constants = [default_circuit_proto()]
+    deserialized_constants = [default_circuit()]
+
+    assert (
+        gateset.deserialize_op(
+            proto, constants=constants, deserialized_constants=deserialized_constants
+        )
+        == circuit_op
+    )