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Add num_qubits to DepolarizingChannel cirq_google serialization #7502

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Merged
dstrain115 merged 2 commits into from
Jul 18, 2025
Merged

Add num_qubits to DepolarizingChannel cirq_google serialization #7502

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6a806e1
Add num_qubits to DepolarizingChannel cirq_google serialization
dstrain115 Jul 17, 2025
33188d9
Remove debug and add check for 0 qubits.
dstrain115 Jul 18, 2025
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10 changes: 8 additions & 2 deletions cirq-google/cirq_google/serialization/circuit_serializer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -288,6 +288,7 @@ def _serialize_gate_op(
arg_func_langs.float_arg_to_proto(
gate.p, out=msg.noisechannel.depolarizingchannel.probability
)
msg.noisechannel.depolarizingchannel.num_qubits = len(op.qubits)
elif isinstance(gate, cirq.RandomGateChannel):
arg_func_langs.float_arg_to_proto(
gate.probability, out=msg.noisechannel.randomgatechannel.probability
Expand Down Expand Up @@ -763,9 +764,14 @@ def _deserialize_gate_op(
)
if not isinstance(p, float):
raise ValueError(
f"Depolarizing noise probability {p} " "cannot be symbol or None"
f"Depolarizing noise probability {p} cannot be symbol or None"
) # pragma: nocover
op = cirq.DepolarizingChannel(p=p)(*qubits)
num_qubits = operation_proto.noisechannel.depolarizingchannel.num_qubits
if num_qubits <= 0:
raise ValueError(
f"Depolarizing noise gate must have positive num_qubits: {num_qubits}"
) # pragma: nocover
op = cirq.DepolarizingChannel(p=p, n_qubits=num_qubits)(*qubits)
elif which_channel_type == 'randomgatechannel':
p = arg_func_langs.float_arg_from_proto(
operation_proto.noisechannel.randomgatechannel.probability
Expand Down
15 changes: 14 additions & 1 deletion cirq-google/cirq_google/serialization/circuit_serializer_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -390,11 +390,24 @@ def circuit_proto(json: dict, qubits: list[str]):
cirq.depolarize(0.5)(Q0),
op_proto(
{
'noisechannel': {'depolarizingchannel': {'probability': {'float_value': 0.5}}},
'noisechannel': {
'depolarizingchannel': {'probability': {'float_value': 0.5}, 'num_qubits': 1}
},
'qubit_constant_index': [0],
}
),
),
(
cirq.depolarize(0.5, n_qubits=2)(Q0, Q1),
op_proto(
{
'noisechannel': {
'depolarizingchannel': {'probability': {'float_value': 0.5}, 'num_qubits': 2}
},
'qubit_constant_index': [0, 1],
}
),
),
(
cirq.X(Q0).with_probability(0.5),
op_proto(
Expand Down