Prepare 0.8 release (#1207)

* Organize 0.8 release notes

* Update min terra version

* Apply suggestions from code review

* Fix reno syntax issue

* Move release notes to a a 0.8 directory

Co-authored-by: Matthew Treinish <mtreinish@kortar.org>

releasenotes/notes/0.8/0.8-release-179e83619783737f.yaml

@@ -0,0 +1,70 @@
+---
+prelude: |
+    The 0.8 release includes several new features and bug fixes. The
+    highlights for this release are: the introduction of a unified
+    :class:`~qiskit.provider.aer.AerSimulator` backend for running circuit
+    simulations using any of the supported simulation methods; a simulator
+    instruction library (:mod:`~qiskit.providers.aer.library`)
+    which includes custom instructions for saving various kinds of simulator
+    data; MPI support for running large simulations on a distributed
+    computing environment.
+features:
+  - |
+    This release includes support for building qiskit-aer with MPI support to
+    run large simulations on a distributed computing environment. See the
+    `contributing guide <https://github.com/Qiskit/qiskit-aer/blob/master/CONTRIBUTING.md#building-with-mpi-support>`__
+    for instructions on building and running in an MPI environment.
+  - |
+    It is now possible to build qiskit-aer with CUDA enabled in Windows.
+    See the
+    `contributing guide <https://github.com/Qiskit/qiskit-aer/blob/master/CONTRIBUTING.md#building-with-gpu-support>`__
+    for instructions on building from source with GPU support.
+  - |
+    When building the qiskit-aer Python extension from source several build
+    dependencies need to be pre-installed to enable C++ compilation. As a
+    user convenience when building the extension any of these build
+    dependencies which were missing would be automatically installed using
+    ``pip`` prior to the normal ``setuptools`` installation steps, however it was
+    previously was not possible to avoid this automatic installation. To solve
+    this issue a new environment variable ``DISABLE_DEPENDENCY_INSTALL``
+    has been added. If it is set to ``1`` or ``ON`` when building the python
+    extension from source this will disable the automatic installation of these
+    missing build dependencies.
+  - |
+    Adds support for optimized N-qubit Pauli gate (
+    :class:`qiskit.circuit.library.generalized_gates.PauliGate`) to the
+    :class:`~qiskit.providers.aer.StatevectorSimulator`,
+    :class:`~qiskit.providers.aer.UnitarySimulator`, and the
+    statevector and density matrix methods of the
+    :class:`~qiskit.providers.aer.QasmSimulator`.
+upgrade:
+  - |
+    The minimum version of `Conan <https://conan.io/>`__ has been increased to 1.31.2.
+    This was necessary to fix a compatibility issue with newer versions of the
+    `urllib3 <https://pypi.org/project/urllib3/>`__ (which is a dependency of Conan).
+    It also adds native support for AppleClang 12 which is useful for users with
+    new Apple computers.
+  - |
+    ``pybind11`` minimum version required is 2.6 instead of 2.4. This is needed
+    in order to support CUDA enabled compilation in Windows.
+  - |
+    Cython has been removed as a build dependency.
+  - |
+    Removed x90 gate decomposition from noise models that was deprecated
+    in qiskit-aer 0.7. This decomposition is now done by using regular
+    noise model basis gates and the qiskit transpiler.
+fixes:
+  - |
+    Fixes bug with the :meth:`~qiskit.providers.aer.QasmSimulator.from_backend`
+    method of the :class:`~qiskit.provider.aer.QasmSimulator` that would set the
+    ``local`` attribute of the configuration to the backend value rather than
+    always being set to ``True``.
+  - |
+    Fixes bug in
+    :meth:`~qiskit.providers.aer.noise.NoiseModel.from_backend` and
+    :meth:`~qiskit.providers.aer.QasmSimulator.from_backend` where
+    :attr:`~qiskit.providers.aer.noise.NoiseModel.basis_gates` was set
+    incorrectly for IBMQ devices with basis gate set
+    ``['id', 'rz', 'sx', 'x', 'cx']``. Now the noise model will always
+    have the same basis gates as the backend basis gates regardless of
+    whether those instructions have errors in the noise model or not.

releasenotes/notes/add-new-backend-interface-5d8c1b5c7d47c50c.yaml → releasenotes/notes/0.8/add-new-backend-interface-5d8c1b5c7d47c50c.yaml

@@ -1,7 +1,8 @@
 ---
 features:
   - |
-    The :meth:`~qiskit.providers.aer.QasmSimulator.run` method for the 
+    The :meth:`~qiskit.providers.aer.AerSimulator.run` method for the
+    :class:`~qiskit.providers.aer.AerSimulator`,
     :class:`~qiskit.providers.aer.QasmSimulator`,
     :class:`~qiskit.providers.aer.StatevectorSimulator`, and
     :class:`~qiskit.providers.aer.UnitarySimulator` backends now takes a
@@ -16,7 +17,7 @@ features:
 
       from qiskit.providers.aer import Aer
 
-      backend = Aer.get_backend('qasm_simulator')
+      backend = Aer.get_backend('aer_simulator')
 
       circuit = QuantumCircuit(2)
       qc.h(0)

releasenotes/notes/0.8/aer-simulator-be393c2caaabb609.yaml

@@ -0,0 +1,81 @@
+---
+features:
+  - |
+    Adds the new :class:`~qiskit.provider.aer.AerSimulator` simulator backend
+    supporting the following simulation methods
+  
+      * `automatic`
+      * `statevector`
+      * `stabilizer`
+      * `density_matrix`
+      * `matrix_product_state` 
+      * `unitary`
+      * `superop`
+
+    The default `automatic` method will automatically choose a simulation
+    method separately for each run circuit based on the circuit instructions
+    and noise model (if any). Initializing a simulator with a specific
+    method can be done using the `method` option.
+
+    .. code::python
+
+      from qiskit.providers.aer import AerSimulator
+
+      # Create a MPS simulator backend
+      backend = AerSimulator(method='matrix_product_state')
+
+    GPU simulation for the statevector, density matrix and unitary methods
+    can be enabled by setting the `device='GPU'` backend option.
+    
+    .. code::python
+
+      from qiskit.providers.aer import AerSimulator
+
+      # Create a GPU statevector backend
+      backend = AerSimulator(method='statevector', device='GPU')
+
+    Note that the `unitary` and `superop` methods do not support measurement
+    as they simulate the unitary matrix or superopator matrix of the run
+    circuit so one of the new :func:`~qiskit.provider.aer.library.save_unitary`,
+    :func:`~qiskit.provider.aer.library.save_superop`, or
+    :func:`~qiskit.provider.aer.library.save_state` instructions must
+    be used to save the simulator state to the returned results. Similarly
+    state of the other simulations methods can be saved using the
+    appropriate instructions. See the :mod:`qiskit.provider.aer.library`
+    API documents for more details.
+
+    Note that the :class:`~qiskit.provider.aer.AerSimulator` simulator
+    superceds the :class:`~qiskit.provider.aer.QasmSimulator`,
+    :class:`~qiskit.provider.aer.StatevectorSimulator`, and
+    :class:`~qiskit.provider.aer.UnitarySimulator` backends which will
+    be deprecated in a future release.   
+  - |
+    Updates the :class:`~qiskit.providers.aer.AerProvider` class to include
+    multiple :class:`~qiskit.provider.aer.AerSimulator` backends preconfigured
+    for all available simulation methods and simulation devices. The new
+    backends can be accessed through the provider interface using the names
+
+      * `"aer_simulator"`
+      * `"aer_simulator_statevector"`
+      * `"aer_simulator_stabilizer"`
+      * `"aer_simulator_density_matrix"`
+      * `"aer_simulator_matrix_product_state"`
+      * `"aer_simulator_extended_stabilizer"`
+      * `"aer_simulator_unitary"`
+      * `"aer_simulator_superop"`
+
+    Additional if Aer was installed with GPU support on a compatible system
+    the following GPU backends will also be available
+
+      * `"aer_simulator_statevector_gpu"`
+      * `"aer_simulator_density_matrix_gpu"`
+      * `"aer_simulator_unitary_gpu"`
+
+    Example
+
+    .. code::python
+
+      from qiskit import Aer
+
+      # Get the GPU statevector simulator backend
+      backend = Aer.get_backend('aer_simulator_statevector_gpu')

releasenotes/notes/extended_stabilizer_norm_estimation-d17632efe8d2bb19.yaml → releasenotes/notes/0.8/extended_stabilizer_norm_estimation-d17632efe8d2bb19.yaml

@@ -1,28 +1,33 @@
 ---
 features:
   - |
-    Introduce a new method for performing measurements with the Extended
-    Stabilizer simulator, called Norm Estimation. This method can be used by passing
-    the following options to the ``QasmSimulator`` provider::
+    Added a new ``norm estimation`` method for performing measurements when using
+    the `"extended_stabilizer"` simulation method. This norm estimation method
+    can be used by passing the following options to the
+    :class:`~qiskit.providers.aer.AerSimulator` and
+    :class:`~qiskit.providers.aer.QasmSimulator` backends
+
+    .. code::python
 
       simulator = QasmSimulator(
-          method='extended_stabilizer,
-          extended_stabilizer_sampling_method="norm_estimation"
-      )
+          method='extended_stabilizer',
+          extended_stabilizer_sampling_method='norm_estimation')
 
     The norm estimation method is slower than the alternative `metropolis`
     or `resampled_metropolis` options, but gives better performance on circuits
-    with sparse output distributions. See the documentation of the ``QasmSimulator``
-    provider for more information.
+    with sparse output distributions. See the documentation of the
+    :class:`~qiskit.providers.aer.QasmSimulator` for more information.
 fixes:
   - |
-    Fixes an issue where the Extended Stabilizer simulator would give incorrect
-    results on quantum circuits with sparse output distributions. Refer to
-    `#306 <https://github.com/Qiskit/qiskit-aer/issues/306>` for more information
-    and examples.
+    Fixes an issue where the Extended `"extended_stabilizer"` simulation method
+    would give incorrect results on quantum circuits with sparse output
+    distributions. Refer to
+    `#306 <https://github.com/Qiskit/qiskit-aer/issues/306>` for more
+    information and examples.
 upgrade:
   - |
-    The following options for the Extended Stabilizer simulator have changed.
+    The following options for the `"extended_stabilizer"` simulation method
+    have changed.
 
       + ``extended_stabilizer_measure_sampling``: This option has been replaced
         by the options ``extended_stabilizer_sampling_method``, which controls

releasenotes/notes/save-data-instructions-24b127612c9f6502.yaml → releasenotes/notes/0.8/instructions-c7ab21d4e9ed8a10.yaml

@@ -24,6 +24,12 @@ features:
 
     See the :mod:`qiskit.providers.aer.library` API documentation
     for details on method compatibility for each instruction.
+
+    Note that the snapshot instructions
+    :class:`~qiskit.providers.aer.extensions.SnapshotStatevector`,
+    :class:`~qiskit.providers.aer.extensions.SnapshotDensityMatrix`,
+    :class:`~qiskit.providers.aer.extensions.SnapshotStabilizer` are
+    still supported but will be deprecated in a future release.
   - |  
     Adds :class:`qiskit.providers.aer.library.SaveExpectationValue` and
     :class:`qiskit.providers.aer.library.SaveExpectationValueVariance`
@@ -35,6 +41,10 @@ features:
     :class:`~qiskit.providers.aer.library.save_expectation_value` and
     :class:`~qiskit.providers.aer.library.save_expectation_value_variance`
     circuit methods which is added to ``QuantumCircuit`` when importing Aer.
+
+    Note that the snapshot instruction
+    :class:`~qiskit.providers.aer.extensions.SnapshotExpectationValue`,
+    is still supported but will be deprecated in a future release.
   - |
     Adds :class:`qiskit.providers.aer.library.SaveProbabilities` and
     :class:`qiskit.providers.aer.library.SaveProbabilitiesDict` quantum
@@ -44,6 +54,10 @@ features:
     :class:`~qiskit.providers.aer.library.save_probabilities` and
     :class:`~qiskit.providers.aer.library.save_probabilities_dict` circuit
     methods which is added to ``QuantumCircuit`` when importing Aer.
+
+    Note that the snapshot instruction
+    :class:`~qiskit.providers.aer.extensions.SnapshotProbabilities`,
+    is still supported but will be deprecated in a future release.
   - |
     Adds :class:`qiskit.providers.aer.library.SaveAmplitudes` and
     :class:`qiskit.providers.aer.library.SaveAmplitudesSquared`
@@ -53,3 +67,23 @@ features:
     :class:`~qiskit.providers.aer.library.save_amplitudes` and
     :class:`~qiskit.providers.aer.library.save_amplitudes_squared`circuit
     methods which is added to ``QuantumCircuit`` when importing Aer.
+  - |
+    Adds instructions for setting the state of the simulators. These
+    instructions must be defined on the full number of qubits in the circuit.
+    They can be applied at any point in a circuit and will override the
+    simulator state with the one specified. Added instructions are
+
+    * :class:`qiskit.providers.aer.library.SetDensityMatrix`
+    * :class:`qiskit.providers.aer.library.SetStabilizer`
+    * :class:`qiskit.providers.aer.library.SetStatevector`
+    * :class:`qiskit.providers.aer.library.SetUnitary`
+    
+    These instruction can be appended to a quantum circuit by using the
+    :class:`~qiskit.providers.aer.library.set_density_matrix`,
+    :class:`~qiskit.providers.aer.library.set_stabilizer`,
+    :class:`~qiskit.providers.aer.library.set_statevector`,
+    :class:`~qiskit.providers.aer.library.set_unitary`
+    circuit methods which are added to ``QuantumCircuit`` when importing Aer.
+
+    See the :mod:`qiskit.providers.aer.library` API documentation
+    for details on method compatibility for each instruction.

releasenotes/notes/0.8/mps-4f8541d5b4bf1c18.yaml

@@ -0,0 +1,15 @@
+---
+features:
+  - |
+    Added support for diagonal gates to the `"matrix_product_state"` simulation
+    method.
+  - |
+    Added support for the ``initialize`` instruction to the
+    `"matrix_product_state"` simulation method.
+issues:
+  - |
+    There is a known issue where the simulation of certain circuits with a Kraus
+    noise model using the `"matrix_product_state"` simulation method can cause
+    the simulator to crash. Refer to
+    `#306 <https://github.com/Qiskit/qiskit-aer/issues/1184>` for more
+    information.