Remove deprecated BackendV1 elements, including base class, providers.models and qobj modules

docs/apidoc/index.rst

@@ -50,7 +50,6 @@ Primitives and providers:
    providers
    providers_basic_provider
    providers_fake_provider
-   providers_models
 
 Results and visualizations:
 
@@ -83,5 +82,4 @@ Other:
 
    compiler
    exceptions
-   qobj
    utils

qiskit/compiler/transpiler.py

@@ -22,7 +22,6 @@
 from qiskit.circuit.quantumcircuit import QuantumCircuit
 from qiskit.dagcircuit import DAGCircuit
 from qiskit.providers.backend import Backend
-from qiskit.providers.backend_compat import BackendV2Converter
 from qiskit.pulse import Schedule
 from qiskit.transpiler import Layout, CouplingMap, PropertySet
 from qiskit.transpiler.basepasses import BasePass
@@ -95,21 +94,20 @@ def transpile(  # pylint: disable=too-many-return-statements
     (``basis_gates``, ``coupling_map``, ``instruction_durations``,
     ``dt`` or ``timing_constraints``). If a ``backend`` is provided together with any loose constraint
     from the list above, the loose constraint will take priority over the corresponding backend
-    constraint. This behavior is independent of whether the ``backend`` instance is of type
-    :class:`.BackendV1` or :class:`.BackendV2`, as summarized in the table below. The first column
+    constraint. This behavior is summarized in the table below. The first column
     in the table summarizes the potential user-provided constraints, and each cell shows whether
     the priority is assigned to that specific constraint input or another input
-    (`target`/`backend(V1)`/`backend(V2)`).
-
-    ============================ ========= ======================== =======================
-    User Provided                target    backend(V1)              backend(V2)
-    ============================ ========= ======================== =======================
-    **basis_gates**              target    basis_gates              basis_gates
-    **coupling_map**             target    coupling_map             coupling_map
-    **instruction_durations**    target    instruction_durations    instruction_durations
-    **dt**                       target    dt                       dt
-    **timing_constraints**       target    timing_constraints       timing_constraints
-    ============================ ========= ======================== =======================
+    (`target`/`backend(V2)`).
+
+    ============================ ========= ========================
+    User Provided                target    backend(V2)
+    ============================ ========= ========================
+    **basis_gates**              target    basis_gates
+    **coupling_map**             target    coupling_map
+    **instruction_durations**    target    instruction_durations
+    **dt**                       target    dt
+    **timing_constraints**       target    timing_constraints
+    ============================ ========= ========================
 
     Args:
         circuits: Circuit(s) to transpile
@@ -320,30 +318,6 @@ def callback_func(**kwargs):
         config = user_config.get_config()
         optimization_level = config.get("transpile_optimization_level", 2)
 
-    if backend is not None and getattr(backend, "version", 0) <= 1:
-        warnings.warn(
-            "The `transpile` function will stop supporting inputs of "
-            f"type `BackendV1` ( {backend} ) in the `backend` parameter in a future "
-            "release no earlier than 2.0. `BackendV1` is deprecated and implementations "
-            "should move to `BackendV2`.",
-            category=DeprecationWarning,
-            stacklevel=2,
-        )
-        with warnings.catch_warnings():
-            # This is a temporary conversion step to allow for a smoother transition
-            # to a fully target-based transpiler pipeline while maintaining the behavior
-            # of `transpile` with BackendV1 inputs.
-            # TODO BackendV1 is deprecated and this path can be
-            #   removed once it gets removed:
-            #   https://github.com/Qiskit/qiskit/pull/12850
-            warnings.filterwarnings(
-                "ignore",
-                category=DeprecationWarning,
-                message=r".+qiskit\.providers\.backend_compat\.BackendV2Converter.+",
-                module="qiskit",
-            )
-            backend = BackendV2Converter(backend)
-
     if (
         scheduling_method is not None
         and backend is None

qiskit/primitives/backend_estimator_v2.py

@@ -23,7 +23,7 @@
 
 from qiskit.circuit import ClassicalRegister, QuantumCircuit, QuantumRegister
 from qiskit.exceptions import QiskitError
-from qiskit.providers import BackendV1, BackendV2
+from qiskit.providers import BackendV2
 from qiskit.quantum_info import Pauli, PauliList
 from qiskit.result import Counts, Result
 from qiskit.transpiler import PassManager, PassManagerConfig
@@ -38,7 +38,7 @@
 
 def _run_circuits(
     circuits: QuantumCircuit | list[QuantumCircuit],
-    backend: BackendV1 | BackendV2,
+    backend: BackendV2,
     clear_metadata: bool = True,
     **run_options,
 ) -> tuple[list[Result], list[dict]]:
@@ -59,9 +59,7 @@ def _run_circuits(
         metadata.append(circ.metadata)
         if clear_metadata:
             circ.metadata = {}
-    if isinstance(backend, BackendV1):
-        max_circuits = getattr(backend.configuration(), "max_experiments", None)
-    elif isinstance(backend, BackendV2):
+    if isinstance(backend, BackendV2):
         max_circuits = backend.max_circuits
     else:
         raise RuntimeError("Backend version not supported")
@@ -174,7 +172,7 @@ class BackendEstimatorV2(BaseEstimatorV2):
 
     The :class:`~.BackendEstimatorV2` class is a generic implementation of the
     :class:`~.BaseEstimatorV2` interface that is used to wrap a :class:`~.BackendV2`
-    (or :class:`~.BackendV1`) object in the :class:`~.BaseEstimatorV2` API. It
+    object in the :class:`~.BaseEstimatorV2` API. It
     facilitates using backends that do not provide a native
     :class:`~.BaseEstimatorV2` implementation in places that work with
     :class:`~.BaseEstimatorV2`. However,
@@ -225,7 +223,7 @@ class BackendEstimatorV2(BaseEstimatorV2):
     def __init__(
         self,
         *,
-        backend: BackendV1 | BackendV2,
+        backend: BackendV2,
         options: dict | None = None,
     ):
         """
@@ -251,7 +249,7 @@ def options(self) -> Options:
         return self._options
 
     @property
-    def backend(self) -> BackendV1 | BackendV2:
+    def backend(self) -> BackendV2:
         """Returns the backend which this sampler object based on."""
         return self._backend
 

qiskit/primitives/backend_sampler_v2.py

@@ -36,7 +36,7 @@
 from qiskit.primitives.containers.bit_array import _min_num_bytes
 from qiskit.primitives.containers.sampler_pub import SamplerPub
 from qiskit.primitives.primitive_job import PrimitiveJob
-from qiskit.providers.backend import BackendV1, BackendV2
+from qiskit.providers.backend import BackendV2
 from qiskit.result import Result
 
 
@@ -83,7 +83,7 @@ class BackendSamplerV2(BaseSamplerV2):
 
     The :class:`~.BackendSamplerV2` class is a generic implementation of the
     :class:`~.BaseSamplerV2` interface that is used to wrap a :class:`~.BackendV2`
-    (or :class:`~.BackendV1`) object in the class :class:`~.BaseSamplerV2` API. It
+    object in the class :class:`~.BaseSamplerV2` API. It
     facilitates using backends that do not provide a native
     :class:`~.BaseSamplerV2` implementation in places that work with
     :class:`~.BaseSamplerV2`. However,
@@ -119,7 +119,7 @@ class BackendSamplerV2(BaseSamplerV2):
     def __init__(
         self,
         *,
-        backend: BackendV1 | BackendV2,
+        backend: BackendV2,
         options: dict | None = None,
     ):
         """
@@ -132,7 +132,7 @@ def __init__(
         self._options = Options(**options) if options else Options()
 
     @property
-    def backend(self) -> BackendV1 | BackendV2:
+    def backend(self) -> BackendV2:
         """Returns the backend which this sampler object based on."""
         return self._backend
 

qiskit/providers/__init__.py

@@ -21,7 +21,7 @@
 provider is anything that provides an external service to Qiskit. The typical
 example of this is a Backend provider which provides
 :class:`~qiskit.providers.Backend` objects which can be used for executing
-:class:`~qiskit.circuit.QuantumCircuit` and/or :class:`~qiskit.pulse.Schedule`
+:class:`~qiskit.circuit.QuantumCircuit`
 objects. This module contains the abstract classes which are used to define the
 interface between a provider and Qiskit.
 
@@ -82,11 +82,8 @@
    :toctree: ../stubs/
 
    Backend
-   BackendV1
    BackendV2
    QubitProperties
-   BackendV2Converter
-   convert_to_target
 
 Options
 -------
@@ -117,10 +114,8 @@
 ----------
 
 .. autoexception:: QiskitBackendNotFoundError
-.. autoexception:: BackendPropertyError
 .. autoexception:: JobError
 .. autoexception:: JobTimeoutError
-.. autoexception:: BackendConfigurationError
 
 Writing a New Backend
 =====================
@@ -559,7 +554,7 @@ def _default_options(cls):
 For some backends (mainly local simulators) the execution of circuits is a
 synchronous operation and there is no need to return a handle to a running job
 elsewhere. For sync jobs its expected that the
-:obj:`~qiskit.providers.BackendV1.run` method on the backend will block until a
+:obj:`~qiskit.providers.BackendV2.run` method on the backend will block until a
 :class:`~qiskit.result.Result` object is generated and the sync job will return
 with that inner :class:`~qiskit.result.Result` object.
 
@@ -603,7 +598,6 @@ def result(self, timeout=None, wait=5):
                 'backend_name': self._backend.configuration().backend_name,
                 'backend_version': self._backend.configuration().backend_version,
                 'job_id': self._job_id,
-                'qobj_id': ', '.join(x.name for x in self.circuits),
                 'success': True,
             })
 
@@ -666,118 +660,12 @@ def status(self):
 implementations. Also, the built-in implementations: :class:`~.Sampler`,
 :class:`~.Estimator`, :class:`~.BackendSampler`, and :class:`~.BackendEstimator`
 can serve as references/models on how to implement these as well.
-
-Migrating from BackendV1 to BackendV2
-=====================================
-
-The :obj:`~BackendV2` class re-defined user access for most properties of a
-backend to make them work with native Qiskit data structures and have flatter
-access patterns. However this means when using a provider that upgrades
-from :obj:`~BackendV1` to :obj:`~BackendV2` existing access patterns will need
-to be adjusted. It is expected for existing providers to deprecate the old
-access where possible to provide a graceful migration, but eventually users
-will need to adjust code. The biggest change to adapt to in :obj:`~BackendV2` is
-that most of the information accessible about a backend is contained in its
-:class:`~qiskit.transpiler.Target` object and the backend's attributes often query
-its :attr:`~qiskit.providers.BackendV2.target`
-attribute to return information, however in many cases the attributes only provide
-a subset of information the target can contain. For example, ``backend.coupling_map``
-returns a :class:`~qiskit.transpiler.CouplingMap` constructed from the
-:class:`~qiskit.transpiler.Target` accessible in the
-:attr:`~qiskit.providers.BackendV2.target` attribute, however the target may contain
-instructions that operate on more than two qubits (which can't be represented in a
-:class:`~qiskit.transpiler.CouplingMap`) or has instructions that only operate on
-a subset of qubits (or two qubit links for a two qubit instruction) which won't be
-detailed in the full coupling map returned by
-:attr:`~qiskit.providers.BackendV2.coupling_map`. So depending on your use case
-it might be necessary to look deeper than just the equivalent access with
-:obj:`~BackendV2`.
-
-Below is a table of example access patterns in :obj:`~BackendV1` and the new form
-with :obj:`~BackendV2`:
-
-.. list-table:: Migrate from :obj:`~BackendV1` to :obj:`~BackendV2`
-   :header-rows: 1
-
-   * - :obj:`~BackendV1`
-     - :obj:`~BackendV2`
-     - Notes
-   * - ``backend.configuration().n_qubits``
-     - ``backend.num_qubits``
-     -
-   * - ``backend.configuration().coupling_map``
-     - ``backend.coupling_map``
-     - The return from :obj:`~BackendV2` is a :class:`~qiskit.transpiler.CouplingMap` object.
-       while in :obj:`~BackendV1` it is an edge list. Also this is just a view of
-       the information contained in ``backend.target`` which may only be a subset of the
-       information contained in :class:`~qiskit.transpiler.Target` object.
-   * - ``backend.configuration().backend_name``
-     - ``backend.name``
-     -
-   * - ``backend.configuration().backend_version``
-     - ``backend.backend_version``
-     - The :attr:`~qiskit.providers.BackendV2.version` attribute represents
-       the version of the abstract :class:`~qiskit.providers.Backend` interface
-       the object implements while :attr:`~qiskit.providers.BackendV2.backend_version`
-       is metadata about the version of the backend itself.
-   * - ``backend.configuration().basis_gates``
-     - ``backend.operation_names``
-     - The :obj:`~BackendV2` return is a list of operation names contained in the
-       ``backend.target`` attribute. The :class:`~qiskit.transpiler.Target` may contain more
-       information that can be expressed by this list of names. For example, that some
-       operations only work on a subset of qubits or that some names implement the same gate
-       with different parameters.
-   * - ``backend.configuration().dt``
-     - ``backend.dt``
-     -
-   * - ``backend.configuration().dtm``
-     - ``backend.dtm``
-     -
-   * - ``backend.configuration().max_experiments``
-     - ``backend.max_circuits``
-     -
-   * - ``backend.configuration().online_date``
-     - ``backend.online_date``
-     -
-   * - ``InstructionDurations.from_backend(backend)``
-     - ``backend.instruction_durations``
-     -
-   * - ``backend.defaults().instruction_schedule_map``
-     - ``backend.instruction_schedule_map``
-     -
-   * - ``backend.properties().t1(0)``
-     - ``backend.qubit_properties(0).t1``
-     -
-   * - ``backend.properties().t2(0)``
-     - ``backend.qubit_properties(0).t2``
-     -
-   * - ``backend.properties().frequency(0)``
-     - ``backend.qubit_properties(0).frequency``
-     -
-   * - ``backend.properties().readout_error(0)``
-     - ``backend.target["measure"][(0,)].error``
-     - In :obj:`~BackendV2` the error rate for the :class:`~qiskit.circuit.library.Measure`
-       operation on a given qubit is used to model the readout error. However a
-       :obj:`~BackendV2` can implement multiple measurement types and list them
-       separately in a :class:`~qiskit.transpiler.Target`.
-   * - ``backend.properties().readout_length(0)``
-     - ``backend.target["measure"][(0,)].duration``
-     - In :obj:`~BackendV2` the duration for the :class:`~qiskit.circuit.library.Measure`
-       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.
 """
 
 # Providers interface
 from qiskit.providers.backend import Backend
-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
@@ -786,7 +674,5 @@ def status(self):
     JobError,
     JobTimeoutError,
     QiskitBackendNotFoundError,
-    BackendPropertyError,
-    BackendConfigurationError,
 )
 from qiskit.providers.jobstatus import JobStatus