From 1b724ded1cf9f581e47c7786396e07c95d35320f Mon Sep 17 00:00:00 2001
From: Orion Martin <40585662+95-martin-orion@users.noreply.github.com>
Date: Thu, 31 Mar 2022 15:36:52 -0700
Subject: [PATCH] Add Google-specific variant for noise properties. (#5082)

This PR provides an implementation of `SuperconductingQubitsNoiseProperties` for Google hardware. Now that SQNP is an abstract type, this is a prerequisite for re-enabling calibration-to-noise tools.

This is part 3 of #4666; part 2 was #4964. Remaining steps include:

- Reinstatement of calibration_to_noise_properties using new types
- Reinstatement of compare_generated_noise_to_metrics using new types
---
 cirq/devices/noise_properties.py                       | 10 +++++++---
 cirq/devices/noise_properties_test.py                  |  8 ++++++++
 .../devices/superconducting_qubits_noise_properties.py |  7 ++++---
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/cirq/devices/noise_properties.py b/cirq/devices/noise_properties.py
index a2ee49ff0fd..1c10d31bb52 100644
--- a/cirq/devices/noise_properties.py
+++ b/cirq/devices/noise_properties.py
@@ -22,7 +22,7 @@
 import abc
 from typing import Iterable, Sequence, TYPE_CHECKING, List
 
-from cirq import _import, ops, protocols, devices
+from cirq import _compat, _import, ops, protocols, devices
 from cirq.devices.noise_utils import (
     PHYSICAL_GATE_TAG,
 )
@@ -54,7 +54,7 @@ def __init__(self, noise_properties: NoiseProperties) -> None:
         self._noise_properties = noise_properties
         self.noise_models = self._noise_properties.build_noise_models()
 
-    def virtual_predicate(self, op: 'cirq.Operation') -> bool:
+    def is_virtual(self, op: 'cirq.Operation') -> bool:
         """Returns True if an operation is virtual.
 
         Device-specific subclasses should implement this method to mark any
@@ -68,6 +68,10 @@ def virtual_predicate(self, op: 'cirq.Operation') -> bool:
         """
         return False
 
+    @_compat.deprecated(deadline='v0.16', fix='Use is_virtual instead.')
+    def virtual_predicate(self, op: 'cirq.Operation') -> bool:
+        return self.is_virtual(op)
+
     def noisy_moments(
         self, moments: Iterable['cirq.Moment'], system_qubits: Sequence['cirq.Qid']
     ) -> Sequence['cirq.OP_TREE']:
@@ -91,7 +95,7 @@ def noisy_moments(
         # using `self.virtual_predicate` to determine virtuality.
         new_moments = []
         for moment in split_measure_moments:
-            virtual_ops = {op for op in moment if self.virtual_predicate(op)}
+            virtual_ops = {op for op in moment if self.is_virtual(op)}
             physical_ops = [
                 op.with_tags(PHYSICAL_GATE_TAG) for op in moment if op not in virtual_ops
             ]
diff --git a/cirq/devices/noise_properties_test.py b/cirq/devices/noise_properties_test.py
index c848af659b3..582e5754e89 100644
--- a/cirq/devices/noise_properties_test.py
+++ b/cirq/devices/noise_properties_test.py
@@ -60,3 +60,11 @@ def test_sample_model():
         cirq.Moment(cirq.H(q0), cirq.H(q1)),
     )
     assert noisy_circuit == expected_circuit
+
+
+def test_deprecated_virtual_predicate():
+    q0, q1 = cirq.LineQubit.range(2)
+    props = SampleNoiseProperties([q0, q1], [(q0, q1), (q1, q0)])
+    model = NoiseModelFromNoiseProperties(props)
+    with cirq.testing.assert_deprecated("Use is_virtual", deadline="v0.16"):
+        _ = model.virtual_predicate(cirq.X(q0))
diff --git a/cirq/devices/superconducting_qubits_noise_properties.py b/cirq/devices/superconducting_qubits_noise_properties.py
index 43a165e89f9..64e307d4623 100644
--- a/cirq/devices/superconducting_qubits_noise_properties.py
+++ b/cirq/devices/superconducting_qubits_noise_properties.py
@@ -35,14 +35,15 @@ class SuperconductingQubitsNoiseProperties(devices.NoiseProperties, abc.ABC):
 
     Args:
         gate_times_ns: Dict[type, float] of gate types to their duration on
-            quantum hardware.
+            quantum hardware. Used with t(1|phi)_ns to specify thermal noise.
         t1_ns: Dict[cirq.Qid, float] of qubits to their T_1 time, in ns.
         tphi_ns: Dict[cirq.Qid, float] of qubits to their T_phi time, in ns.
         readout_errors: Dict[cirq.Qid, np.ndarray] of qubits to their readout
             errors in matrix form: [P(read |1> from |0>), P(read |0> from |1>)].
+            Used to prepend amplitude damping errors to measurements.
         gate_pauli_errors: dict of noise_utils.OpIdentifiers (a gate and the qubits it
-            targets) to the Pauli error for that operation. Keys in this dict
-            must have defined qubits.
+            targets) to the Pauli error for that operation. Used to construct
+            depolarizing error. Keys in this dict must have defined qubits.
         validate: If True, verifies that t1 and tphi qubits sets match, and
             that all symmetric two-qubit gates have errors which are
             symmetric over the qubits they affect. Defaults to True.