Temporary GridDevice.qubits property

quantumlib · Jun 23, 2022 · 7e62a15 · 7e62a15
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diff --git a/cirq-google/cirq_google/devices/grid_device.py b/cirq-google/cirq_google/devices/grid_device.py
@@ -305,6 +305,15 @@ def metadata(self) -> cirq.GridDeviceMetadata:
         """Get metadata information for the device."""
         return self._metadata
 
+    # Some user code using SerializableDevices gets the qubit list via `device.qubits`.
+    # This is a stopgap solution to prevent user breakage with the change to GridDevice.
+    @property
+    @cirq._compat.deprecated(
+        deadline='v0.16', fix='Change `device.qubits` to `device.metadata.qubit_set`.'
+    )
+    def qubits(self) -> List[cirq.Qid]:
+        return list(self._metadata.qubit_set)
+
     def validate_operation(self, operation: cirq.Operation) -> None:
         """Raises an exception if an operation is not valid.
 

diff --git a/cirq-google/cirq_google/devices/grid_device_test.py b/cirq-google/cirq_google/devices/grid_device_test.py
@@ -517,3 +517,11 @@ def test_to_proto_empty():
     assert len(device.metadata.qubit_pairs) == 0
     assert device.metadata.gateset == cirq.Gateset()
     assert device.metadata.gate_durations is None
+
+
+def test_grid_device_qubits():
+    _, spec = _create_device_spec_with_horizontal_couplings()
+    device = cirq_google.GridDevice.from_proto(spec)
+
+    with cirq.testing.assert_deprecated('device.qubits', deadline='v0.16'):
+        assert frozenset(device.qubits) == device.metadata.qubit_set