Add BackendV2Converter class for treating BackendV1 as BackendV2

qiskit/circuit/library/standard_gates/__init__.py

@@ -103,3 +103,72 @@
 from .z import ZGate, CZGate, CCZGate
 
 from .multi_control_rotation_gates import mcrx, mcry, mcrz
+
+
+def get_standard_gate_name_mapping():
+    """Return a dictionary mapping the name of standard gates and instructions to an object for
+    that name."""
+    from qiskit.circuit.parameter import Parameter
+    from qiskit.circuit.measure import Measure
+    from qiskit.circuit.delay import Delay
+    from qiskit.circuit.reset import Reset
+
+    # Standard gates library mapping, multicontrolled gates not included since they're
+    # variable width
+    gates = [
+        IGate(),
+        SXGate(),
+        XGate(),
+        CXGate(),
+        RZGate(Parameter("λ")),
+        RGate(Parameter("ϴ"), Parameter("φ")),
+        Reset(),
+        C3SXGate(),
+        CCXGate(),
+        DCXGate(),
+        CHGate(),
+        CPhaseGate(Parameter("ϴ")),
+        CRXGate(Parameter("ϴ")),
+        CRYGate(Parameter("ϴ")),
+        CRZGate(Parameter("ϴ")),
+        CSwapGate(),
+        CSXGate(),
+        CUGate(Parameter("ϴ"), Parameter("φ"), Parameter("λ"), Parameter("γ")),
+        CU1Gate(Parameter("λ")),
+        CU3Gate(Parameter("ϴ"), Parameter("φ"), Parameter("λ")),
+        CYGate(),
+        CZGate(),
+        CCZGate(),
+        HGate(),
+        PhaseGate(Parameter("ϴ")),
+        RCCXGate(),
+        RC3XGate(),
+        RXGate(Parameter("ϴ")),
+        RXXGate(Parameter("ϴ")),
+        RYGate(Parameter("ϴ")),
+        RYYGate(Parameter("ϴ")),
+        RZZGate(Parameter("ϴ")),
+        RZXGate(Parameter("ϴ")),
+        XXMinusYYGate(Parameter("ϴ")),
+        XXPlusYYGate(Parameter("ϴ")),
+        ECRGate(),
+        SGate(),
+        SdgGate(),
+        CSGate(),
+        CSdgGate(),
+        SwapGate(),
+        iSwapGate(),
+        SXdgGate(),
+        TGate(),
+        TdgGate(),
+        UGate(Parameter("ϴ"), Parameter("φ"), Parameter("λ")),
+        U1Gate(Parameter("λ")),
+        U2Gate(Parameter("φ"), Parameter("λ")),
+        U3Gate(Parameter("ϴ"), Parameter("φ"), Parameter("λ")),
+        YGate(),
+        ZGate(),
+        Delay(Parameter("t")),
+        Measure(),
+    ]
+    name_mapping = {gate.name: gate for gate in gates}
+    return name_mapping

qiskit/providers/__init__.py

@@ -94,6 +94,8 @@
    BackendV1
    BackendV2
    QubitProperties
+   BackendV2Converter
+   convert_to_target
 
 Options
 -------
@@ -666,6 +668,9 @@ def status(self):
        operation on a given qubit is used to model the readout length. However, a
        :obj:`~BackendV2` can implement multiple measurement types and list them
        separately in a :class:`~qiskit.transpiler.Target`.
+
+There is also a :class:`~.BackendV2Converter` class available that enables you
+to wrap a :class:`~.BackendV1` object with a :class:`~.BackendV2` interface.
 """
 
 import pkgutil
@@ -677,6 +682,8 @@ def status(self):
 from qiskit.providers.backend import BackendV1
 from qiskit.providers.backend import BackendV2
 from qiskit.providers.backend import QubitProperties
+from qiskit.providers.backend_compat import BackendV2Converter
+from qiskit.providers.backend_compat import convert_to_target
 from qiskit.providers.options import Options
 from qiskit.providers.job import Job
 from qiskit.providers.job import JobV1

qiskit/providers/backend_compat.py

@@ -0,0 +1,282 @@
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2020.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Backend abstract interface for providers."""
+
+from __future__ import annotations
+
+from typing import List, Iterable, Any, Dict, Optional
+
+from qiskit.exceptions import QiskitError
+
+from qiskit.providers.backend import BackendV1, BackendV2
+from qiskit.providers.backend import QubitProperties
+from qiskit.utils.units import apply_prefix
+from qiskit.circuit.library.standard_gates import get_standard_gate_name_mapping
+from qiskit.circuit.measure import Measure
+from qiskit.providers.models.backendconfiguration import BackendConfiguration
+from qiskit.providers.models.backendproperties import BackendProperties
+from qiskit.providers.models.pulsedefaults import PulseDefaults
+from qiskit.providers.options import Options
+from qiskit.providers.exceptions import BackendPropertyError
+
+
+def convert_to_target(
+    configuration: BackendConfiguration,
+    properties: BackendProperties = None,
+    defaults: PulseDefaults = None,
+    custom_name_mapping: Optional[Dict[str, Any]] = None,
+    add_delay: bool = False,
+):
+    """Uses configuration, properties and pulse defaults
+    to construct and return Target class.
+    """
+    # pylint: disable=cyclic-import
+    from qiskit.transpiler.target import (
+        Target,
+        InstructionProperties,
+    )
+
+    # Standard gates library mapping, multicontrolled gates not included since they're
+    # variable width
+    name_mapping = get_standard_gate_name_mapping()
+    target = None
+    if custom_name_mapping is not None:
+        name_mapping.update(custom_name_mapping)
+    # Parse from properties if it exsits
+    if properties is not None:
+        qubit_properties = qubit_props_list_from_props(properties=properties)
+        target = Target(num_qubits=configuration.n_qubits, qubit_properties=qubit_properties)
+        # Parse instructions
+        gates: Dict[str, Any] = {}
+        for gate in properties.gates:
+            name = gate.gate
+            if name in name_mapping:
+                if name not in gates:
+                    gates[name] = {}
+            else:
+                raise QiskitError(
+                    f"Operation name {name} does not have a known mapping. Use "
+                    "custom_name_mapping to map this name to an Operation object"
+                )
+
+            qubits = tuple(gate.qubits)
+            gate_props = {}
+            for param in gate.parameters:
+                if param.name == "gate_error":
+                    gate_props["error"] = param.value
+                if param.name == "gate_length":
+                    gate_props["duration"] = apply_prefix(param.value, param.unit)
+            gates[name][qubits] = InstructionProperties(**gate_props)
+        for gate, props in gates.items():
+            inst = name_mapping[gate]
+            target.add_instruction(inst, props)
+        # Create measurement instructions:
+        measure_props = {}
+        for qubit, _ in enumerate(properties.qubits):
+            measure_props[(qubit,)] = InstructionProperties(
+                duration=properties.readout_length(qubit),
+                error=properties.readout_error(qubit),
+            )
+        target.add_instruction(Measure(), measure_props)
+    # Parse from configuration because properties doesn't exist
+    else:
+        target = Target(num_qubits=configuration.n_qubits)
+        for gate in configuration.gates:
+            name = gate.name
+            gate_props = (
+                {tuple(x): None for x in gate.coupling_map}  # type: ignore[misc]
+                if hasattr(gate, "coupling_map")
+                else {None: None}
+            )
+            if name in name_mapping:
+                target.add_instruction(name_mapping[name], gate_props)
+            else:
+                raise QiskitError(
+                    f"Operation name {name} does not have a known mapping. "
+                    "Use custom_name_mapping to map this name to an Operation object"
+                )
+        target.add_instruction(Measure())
+    # parse global configuration properties
+    if hasattr(configuration, "dt"):
+        target.dt = configuration.dt
+    if hasattr(configuration, "timing_constraints"):
+        target.granularity = configuration.timing_constraints.get("granularity")
+        target.min_length = configuration.timing_constraints.get("min_length")
+        target.pulse_alignment = configuration.timing_constraints.get("pulse_alignment")
+        target.aquire_alignment = configuration.timing_constraints.get("acquire_alignment")
+    # If a pulse defaults exists use that as the source of truth
+    if defaults is not None:
+        inst_map = defaults.instruction_schedule_map
+        for inst in inst_map.instructions:
+            for qarg in inst_map.qubits_with_instruction(inst):
+                sched = inst_map.get(inst, qarg)
+                if inst in target:
+                    try:
+                        qarg = tuple(qarg)
+                    except TypeError:
+                        qarg = (qarg,)
+                    if inst == "measure":
+                        for qubit in qarg:
+                            target[inst][(qubit,)].calibration = sched
+                    elif qarg in target[inst]:
+                        target[inst][qarg].calibration = sched
+    combined_global_ops = set()
+    if configuration.basis_gates:
+        combined_global_ops.update(configuration.basis_gates)
+    for op in combined_global_ops:
+        if op not in target:
+            if op in name_mapping:
+                target.add_instruction(
+                    name_mapping[op], {(bit,): None for bit in range(target.num_qubits)}
+                )
+            else:
+                raise QiskitError(
+                    f"Operation name '{op}' does not have a known mapping. Use "
+                    "custom_name_mapping to map this name to an Operation object"
+                )
+    if add_delay and "delay" not in target:
+        target.add_instruction(
+            name_mapping["delay"], {(bit,): None for bit in range(target.num_qubits)}
+        )
+    return target
+
+
+def qubit_props_list_from_props(
+    properties: BackendProperties,
+) -> List[QubitProperties]:
+    """Uses BackendProperties to construct
+    and return a list of QubitProperties.
+    """
+    qubit_props: List[QubitProperties] = []
+    for qubit, _ in enumerate(properties.qubits):
+        try:
+            t_1 = properties.t1(qubit)
+        except BackendPropertyError:
+            t_1 = None
+        try:
+            t_2 = properties.t2(qubit)
+        except BackendPropertyError:
+            t_2 = None
+        try:
+            frequency = properties.frequency(qubit)
+        except BackendPropertyError:
+            frequency = None
+        qubit_props.append(
+            QubitProperties(  # type: ignore[no-untyped-call]
+                t1=t_1,
+                t2=t_2,
+                frequency=frequency,
+            )
+        )
+    return qubit_props
+
+
+class BackendV2Converter(BackendV2):
+    """A converter class that takes a :class:`~.BackendV1` instance and wraps it in a
+    :class:`~.BackendV2` interface.
+
+    This class implements the :class:`~.BackendV2` interface and is used to enable
+    common access patterns between :class:`~.BackendV1` and :class:`~.BackendV2`. This
+    class should only be used if you need a :class:`~.BackendV2` and still need
+    compatibility with :class:`~.BackendV1`.
+    """
+
+    def __init__(
+        self,
+        backend: BackendV1,
+        name_mapping: Optional[Dict[str, Any]] = None,
+        add_delay: bool = False,
+    ):
+        """Initialize a BackendV2 converter instance based on a BackendV1 instance.
+
+        Args:
+            backend: The input :class:`~.BackendV1` based backend to wrap in a
+                :class:`~.BackendV2` interface
+            name_mapping: An optional dictionary that maps custom gate/operation names in
+                ``backend`` to an :class:`~.Operation` object representing that
+                gate/operation. By default most standard gates names are mapped to the
+                standard gate object from :mod:`qiskit.circuit.library` this only needs
+                to be specified if the input ``backend`` defines gates in names outside
+                that set.
+            add_delay: If set to true a :class:`~qiskit.circuit.Delay` operation
+                will be added to the target as a supported operation for all
+                qubits
+        """
+        self._backend = backend
+        self._config = self._backend.configuration()
+        super().__init__(
+            provider=backend.provider,
+            name=backend.name(),
+            description=self._config.description,
+            online_date=self._config.online_date,
+            backend_version=self._config.backend_version,
+        )
+        self._options = self._backend._options
+        self._properties = None
+        if hasattr(self._backend, "properties"):
+            self._properties = self._backend.properties()
+        self._defaults = None
+        self._target = None
+        self._name_mapping = name_mapping
+        self._add_delay = add_delay
+
+    @property
+    def target(self):
+        """A :class:`qiskit.transpiler.Target` object for the backend.
+
+        :rtype: Target
+        """
+        if self._target is None:
+            if self._defaults is None and hasattr(self._backend, "defaults"):
+                self._defaults = self._backend.defaults()
+            if self._properties is None and hasattr(self._backend, "properties"):
+                self._properties = self._backend.properties()
+            self._target = convert_to_target(
+                self._config,
+                self._properties,
+                self._defaults,
+                custom_name_mapping=self._name_mapping,
+                add_delay=self._add_delay,
+            )
+        return self._target
+
+    @property
+    def max_circuits(self):
+        return self._config.max_experiments
+
+    @classmethod
+    def _default_options(cls):
+        return Options()
+
+    @property
+    def dtm(self) -> float:
+        return self._config.dtm
+
+    @property
+    def meas_map(self) -> List[List[int]]:
+        return self._config.dt
+
+    def drive_channel(self, qubit: int):
+        self._config.drive(qubit)
+
+    def measure_channel(self, qubit: int):
+        self._config.measure(qubit)
+
+    def acquire_channel(self, qubit: int):
+        self._config.acquire(qubit)
+
+    def control_channel(self, qubits: Iterable[int]):
+        self._config.control(qubits)
+
+    def run(self, run_input, **options):
+        return self._backend.run(run_input, **options)

releasenotes/notes/backend-converter-05360f12f9042829.yaml

@@ -0,0 +1,15 @@
+---
+features:
+  - |
+    Added a new class, :class:`~BackendV2Converter`, which is used to wrap
+    a :class:`~.BackendV1` instance in a :class:`~.BackendV2` interface. It
+    enables you to have a :class:`~.BackendV2` instance from any
+    :class:`~.BackendV1`. This enables standardizing access patterns on the
+    newer :class:`~.BackendV2` interface even if you still support
+    :class:`~.BackendV1`.
+
+  - |
+    Added a new function :func:`~.convert_to_target` which is used to take
+    a :class:`~.BackendConfiguration`, and optionally a
+    :class:`~.BackendProperties` and :class:`~.PulseDefaults` and create
+    a :class:`~.Target` object equivalent to the contents of those objects.