Add QVM factory function load_device_noise_properties

Convenience function for constructing GoogleNoiseProperties from available
specifications for known QVM device.

Related to b/395705720

Author: pavoljuhas

cirq-google/cirq_google/engine/__init__.py

@@ -87,6 +87,7 @@
     create_noiseless_virtual_engine_from_proto as create_noiseless_virtual_engine_from_proto,
     create_noiseless_virtual_engine_from_templates as create_noiseless_virtual_engine_from_templates,
     create_noiseless_virtual_engine_from_latest_templates as create_noiseless_virtual_engine_from_latest_templates,
+    load_device_noise_properties as load_device_noise_properties,
     load_median_device_calibration as load_median_device_calibration,
     load_sample_device_zphase as load_sample_device_zphase,
 )

cirq-google/cirq_google/engine/virtual_engine_factory.py

@@ -105,6 +105,27 @@ def _create_perfect_calibration(device: cirq.Device) -> calibration.Calibration:
     return calibration.Calibration(calibration=snapshot, metrics=all_metrics)
 
 
+def load_device_noise_properties(processor_id: str) -> cirq_google.GoogleNoiseProperties:
+    """Loads NoiseProperties for the given device.
+
+    This combines calibration data for the device with gate times from its specification, and
+    the Z phases data, if available, to construct NoiseProperties for device simulation.
+
+    Args:
+        processor_id: name of the processor to simulate.
+
+    Raises:
+        ValueError: if processor_id is not a supported QCS processor.
+    """
+    device = create_device_from_processor_id(processor_id)
+    calibration = load_median_device_calibration(processor_id)
+    zphase_data = load_sample_device_zphase(processor_id) if processor_id in ZPHASE_DATA else None
+    gate_times_ns = extract_gate_times_ns_from_device(device)
+    return noise_properties_from_calibration(
+        calibration=calibration, zphase_data=zphase_data, gate_times_ns=gate_times_ns
+    )
+
+
 def load_median_device_calibration(processor_id: str) -> calibration.Calibration:
     """Loads a median `cirq_google.Calibration` for the given device.
 

cirq-google/cirq_google/engine/virtual_engine_factory_test.py

@@ -60,6 +60,15 @@ def test_create_from_device():
     _test_processor(engine.get_processor('sycamore'))
 
 
+def test_load_device_noise_properties() -> None:
+    noise_properties = factory.load_device_noise_properties("rainbow")
+    assert noise_properties.readout_errors[cirq.GridQubit(9, 4)] == [0.0124, 0.0464]
+    assert noise_properties.gate_times_ns[cirq.PhasedXZGate] == 25
+    op_id = cirq.OpIdentifier(cirq.ISwapPowGate, cirq.GridQubit(3, 2), cirq.GridQubit(4, 2))
+    assert noise_properties.fsim_errors[op_id].zeta == -0.004952147720840733
+    assert noise_properties.fsim_errors[op_id].gamma == -0.04094895320428251
+
+
 def test_median_rainbow_device():
     q0, q1 = cirq.GridQubit.rect(1, 2, 5, 3)
     cal = factory.load_median_device_calibration('rainbow')