Add SuperconductingQubitsNoiseProperties (quantumlib#4964)

* Add SuperconductingQubitsNoiseProperties.

* Address review comments.

* Recover from breakages

* linter wrangling

* use cached_property

* nits nits nits

Co-authored-by: Cirq Bot <craiggidney+github+cirqbot@google.com>

Author: 2 people

cirq-core/cirq/__init__.py

@@ -96,6 +96,7 @@
     NoiseModelFromNoiseProperties,
     NoiseProperties,
     OpIdentifier,
+    SuperconductingQubitsNoiseProperties,
     SymmetricalQidPair,
     UNCONSTRAINED_DEVICE,
     NamedTopology,

cirq-core/cirq/devices/__init__.py

@@ -67,6 +67,10 @@
     NoiseProperties,
 )
 
+from cirq.devices.superconducting_qubits_noise_properties import (
+    SuperconductingQubitsNoiseProperties,
+)
+
 from cirq.devices.noise_utils import (
     OpIdentifier,
     decay_constant_to_xeb_fidelity,

cirq-core/cirq/devices/superconducting_qubits_noise_properties.py

@@ -0,0 +1,191 @@
+# Copyright 2021 The Cirq Developers
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+"""Class for representing noise on a superconducting qubit device."""
+
+import abc
+from dataclasses import dataclass, field
+from typing import Dict, TYPE_CHECKING, List, Set, Type
+
+from cirq import _compat, ops, devices
+from cirq.devices import noise_utils
+
+if TYPE_CHECKING:
+    import cirq
+
+
+# TODO: missing per-device defaults
+# Type-ignored because mypy cannot handle abstract dataclasses:
+# https://github.com/python/mypy/issues/5374
+@dataclass  # type: ignore
+class SuperconductingQubitsNoiseProperties(devices.NoiseProperties, abc.ABC):
+    """Noise-defining properties for a superconducting-qubit-based device.
+
+    Args:
+        gate_times_ns: Dict[type, float] of gate types to their duration on
+            quantum hardware.
+        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>)].
+        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.
+        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.
+    """
+
+    gate_times_ns: Dict[type, float]
+    t1_ns: Dict['cirq.Qid', float]
+    tphi_ns: Dict['cirq.Qid', float]
+    readout_errors: Dict['cirq.Qid', List[float]]
+    gate_pauli_errors: Dict[noise_utils.OpIdentifier, float]
+
+    validate: bool = True
+    _qubits: List['cirq.Qid'] = field(init=False, default_factory=list)
+
+    def __post_init__(self):
+        if not self.validate:
+            return
+        t1_qubits = set(self.t1_ns)
+        tphi_qubits = set(self.tphi_ns)
+
+        if t1_qubits != tphi_qubits:
+            raise ValueError('Keys specified for T1 and Tphi are not identical.')
+
+        # validate two qubit gate errors.
+        self._validate_symmetric_errors('gate_pauli_errors')
+
+    def _validate_symmetric_errors(self, field_name: str) -> None:
+        gate_error_dict = getattr(self, field_name)
+        for op_id in gate_error_dict:
+            if len(op_id.qubits) != 2:
+                # single qubit op_ids also present, or generic values are
+                # specified. Skip these cases
+                if len(op_id.qubits) > 2:
+                    raise ValueError(
+                        f'Found gate {op_id.gate_type} with {len(op_id.qubits)} qubits. '
+                        'Symmetric errors can only apply to 2-qubit gates.'
+                    )
+            elif op_id.gate_type in self.symmetric_two_qubit_gates():
+                op_id_swapped = noise_utils.OpIdentifier(op_id.gate_type, *op_id.qubits[::-1])
+                if op_id_swapped not in gate_error_dict:
+                    raise ValueError(
+                        f'Operation {op_id} of field {field_name} has errors '
+                        f'but its symmetric id {op_id_swapped} does not.'
+                    )
+            elif op_id.gate_type not in self.asymmetric_two_qubit_gates():
+                # Asymmetric gates do not require validation.
+                raise ValueError(
+                    f'Found gate {op_id.gate_type} which does not appear in the '
+                    'symmetric or asymmetric gate sets.'
+                )
+
+    @property
+    def qubits(self) -> List['cirq.Qid']:
+        """Qubits for which we have data"""
+        if not self._qubits:
+            self._qubits = sorted(self.t1_ns)
+        return self._qubits
+
+    @classmethod
+    @abc.abstractmethod
+    def single_qubit_gates(cls) -> Set[Type[ops.Gate]]:
+        """Returns the set of single-qubit gates this class supports."""
+
+    @classmethod
+    @abc.abstractmethod
+    def symmetric_two_qubit_gates(cls) -> Set[Type[ops.Gate]]:
+        """Returns the set of symmetric two-qubit gates this class supports."""
+
+    @classmethod
+    @abc.abstractmethod
+    def asymmetric_two_qubit_gates(cls) -> Set[Type[ops.Gate]]:
+        """Returns the set of asymmetric two-qubit gates this class supports."""
+
+    @classmethod
+    def two_qubit_gates(cls) -> Set[Type[ops.Gate]]:
+        """Returns the set of all two-qubit gates this class supports."""
+        return cls.symmetric_two_qubit_gates() | cls.asymmetric_two_qubit_gates()
+
+    @classmethod
+    def expected_gates(cls) -> Set[Type[ops.Gate]]:
+        """Returns the set of all gates this class supports."""
+        return cls.single_qubit_gates() | cls.two_qubit_gates()
+
+    def _get_pauli_error(self, p_error: float, op_id: noise_utils.OpIdentifier):
+        time_ns = float(self.gate_times_ns[op_id.gate_type])
+        for q in op_id.qubits:
+            p_error -= noise_utils.decoherence_pauli_error(self.t1_ns[q], self.tphi_ns[q], time_ns)
+        return p_error
+
+    @_compat.cached_property
+    def _depolarizing_error(self) -> Dict[noise_utils.OpIdentifier, float]:
+        """Returns the portion of Pauli error from depolarization."""
+        depol_errors = {}
+        for op_id, p_error in self.gate_pauli_errors.items():
+            gate_type = op_id.gate_type
+            if issubclass(gate_type, ops.MeasurementGate):
+                # Non-measurement error can be ignored on measurement gates.
+                continue
+            expected_qubits = 1 if gate_type in self.single_qubit_gates() else 2
+            if len(op_id.qubits) != expected_qubits:
+                raise ValueError(
+                    f'Gate {gate_type} takes {expected_qubits} qubit(s), '
+                    f'but {op_id.qubits} were given.'
+                )
+            depol_errors[op_id] = self._get_pauli_error(p_error, op_id)
+        return depol_errors
+
+    def build_noise_models(self) -> List['cirq.NoiseModel']:
+        noise_models: List['cirq.NoiseModel'] = []
+
+        if self.t1_ns:
+            noise_models.append(
+                devices.ThermalNoiseModel(
+                    set(self.t1_ns.keys()),
+                    self.gate_times_ns,
+                    cool_rate_GHz={q: 1 / T1 for q, T1 in self.t1_ns.items()},
+                    dephase_rate_GHz={q: 1 / Tp for q, Tp in self.tphi_ns.items()},
+                )
+            )
+
+        depolarizing_error = self._depolarizing_error
+        added_pauli_errors = {
+            op_id: ops.depolarize(p_error, len(op_id.qubits)).on(*op_id.qubits)
+            for op_id, p_error in depolarizing_error.items()
+            if p_error > 0
+        }
+
+        # This adds per-qubit pauli error after ops on those qubits.
+        noise_models.append(devices.InsertionNoiseModel(ops_added=added_pauli_errors))
+
+        # This adds per-qubit measurement error BEFORE measurement on those qubits.
+        if self.readout_errors:
+            added_measure_errors: Dict[noise_utils.OpIdentifier, 'cirq.Operation'] = {}
+            for qubit in self.readout_errors:
+                p_00, p_11 = self.readout_errors[qubit]
+                p = p_11 / (p_00 + p_11)
+                gamma = p_11 / p
+                added_measure_errors[
+                    noise_utils.OpIdentifier(ops.MeasurementGate, qubit)
+                ] = ops.generalized_amplitude_damp(p, gamma).on(qubit)
+
+            noise_models.append(
+                devices.InsertionNoiseModel(ops_added=added_measure_errors, prepend=True)
+            )
+
+        return noise_models