refactor: remove all deprecated code (qiskit-community#1248)

* refactor: remove all deprecated code

This commit removes all deprecated code. Even though this is done a bit
earlier than originally announced under the Qiskit deprecation policy,
we are taking this step now since this project has become part of a
community effort.
As a direct consequence, new codeowners will soon join the team behind
Qiskit Nature. Rather than handing over a codebase that includes pieces
of code which need attention in the near future (and even continued
support until then) we are removing these parts early.

As a consequence, if you still require parts of this code, we suggest
you stick to Qiskit Nature 0.6 until you can transition based on the
provided migration guides.

This commit also removes the deprecation utilities which are superseded
by the ones provided by Qiskit directly (see qiskit.utils.deprecation).

* docs: remove doctest from migration guides

Now that the old code covered by the migration guide is being removed,
doctest can no longer execute this code. Thus, this commit replaces the
doctest directives with simple code cells.

* docs: add 0.7 prelude

* docs: add spelling exceptions

* docs: fix indent in release note

* fix: remove final occurrence of opflow

* lint: run black

* fix: remove final occurrences of removed setting attributes

* docs: removes a now obsolete release note

* fix: remove left over setting

.pylintdict

@@ -86,6 +86,7 @@ cls
 cmap
 cnot
 codec
+codeowners
 coeff
 coeffs
 colormap
@@ -395,6 +396,7 @@ observables
 occupancies
 ok
 ollitrault
+onboarding
 onee
 oneeints
 onsite

docs/howtos/adapt_vqe.rst

@@ -6,17 +6,6 @@ algorithm has been migrated to Qiskit Terra (released in v0.22).
 
 This tutorial outlines how the algorithm can be used.
 
-0. We ensure the use of :class:`~qiskit.opflow.primitive_ops.PauliSumOp` (this is the default value
-   of this setting for now but we enforce it here to ensure stability of this guide as long as the
-   :class:`~qiskit.algorithms.minimum_eigensolvers.AdaptVQE` class is not yet guaranteed to handle
-   the :class:`~qiskit.quantum_info.SparsePauliOp` successor properly):
-
-.. testcode::
-
-   from qiskit_nature import settings
-
-   settings.use_pauli_sum_op = True
-
 1. We obtain an :class:`~qiskit_nature.second_q.problems.ElectronicStructureProblem`
    which we want to solve:
 

docs/migration/0.6_b_mes_factory.rst

@@ -36,7 +36,7 @@ For the following examples, we need a simple
 :class:`~qiskit_nature.second_q.problems.ElectronicStructureProblem` which we can obtain from a
 :class:`~qiskit_nature.second_q.drivers.PySCFDriver` like so:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit_nature.second_q.drivers import PySCFDriver
    from qiskit_nature.second_q.mappers import ParityMapper
@@ -58,7 +58,7 @@ VQEUCCFactory
 
 The old way:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit.algorithms.optimizers import SLSQP
    from qiskit.primitives import Estimator
@@ -72,13 +72,13 @@ The old way:
    result = solver.compute_minimum_eigenvalue(qubit_op, aux_ops)
    print(f"Eigenvalue = {result.eigenvalue: .6f}")
 
-.. testoutput::
+.. parsed-literal::
 
     Eigenvalue = -1.857275
 
 And the corresponding new way:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit.algorithms.minimum_eigensolvers import VQE
    from qiskit.algorithms.optimizers import SLSQP
@@ -107,7 +107,7 @@ And the corresponding new way:
    result = solver.compute_minimum_eigenvalue(qubit_op, aux_ops)
    print(f"Eigenvalue = {result.eigenvalue: .6f}")
 
-.. testoutput::
+.. parsed-literal::
 
     Eigenvalue = -1.857275
 
@@ -116,7 +116,7 @@ NumPyEigensolverFactory
 
 The old way:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit_nature.second_q.algorithms import NumPyEigensolverFactory
 
@@ -132,15 +132,15 @@ The old way:
    for idx, eigenvalue in enumerate(result.eigenvalues):
        print(f"{idx}: {eigenvalue: .6f}")
 
-.. testoutput::
+.. parsed-literal::
 
     0: -1.857275
     1: -0.882722
     2: -0.224911
 
 And the corresponding new way:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit.algorithms.eigensolvers import NumPyEigensolver
 
@@ -152,7 +152,7 @@ And the corresponding new way:
    for idx, eigenvalue in enumerate(result.eigenvalues):
        print(f"{idx}: {eigenvalue: .6f}")
 
-.. testoutput::
+.. parsed-literal::
 
     0: -1.857275
     1: -0.882722

docs/migration/0.6_c_qubit_converter.rst

@@ -17,7 +17,7 @@ Setup
 For the examples in this guide, we will always be using the following
 :class:`~qiskit_nature.second_q.operators.FermionicOp`:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit_nature.second_q.drivers import PySCFDriver
 
@@ -29,7 +29,7 @@ For the examples in this guide, we will always be using the following
    for label, coeff in sorted(hamiltonian.items()):
        print(f"{coeff:+.8f} * '{label}'")
 
-.. testoutput::
+.. parsed-literal::
 
     +0.33785508 * '+_0 +_0 -_0 -_0'
     +0.09046560 * '+_0 +_0 -_1 -_1'
@@ -80,7 +80,7 @@ now set the value of :attr:`~qiskit_nature.settings.QiskitNatureSettings.use_pau
 To ensure that we can consistently rely on using the :class:`~qiskit.quantum_info.SparsePauliOp` in
 the following parts of this guide, we are applying this setting here:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit_nature import settings
 
@@ -102,7 +102,7 @@ In the simplest cases, all you did was pass a :class:`~qiskit_nature.second_q.ma
 object into the :class:`~qiskit_nature.second_q.mappers.QubitConverter`. For example, somewhat like
 this:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit_nature.second_q.mappers import JordanWignerMapper, QubitConverter
 
@@ -115,14 +115,14 @@ object from the example above into whichever place you were using it before.
 If you were working directly with some :class:`~qiskit_nature.second_q.operators.SparseLabelOp` like
 so:
 
-.. testcode::
+.. code:: ipython3
 
    qubit_op = converter.convert(hamiltonian)
 
    for pauli, coeff in sorted(qubit_op.label_iter()):
        print(f"{coeff.real:+.8f} * {pauli}")
 
-.. testoutput::
+.. parsed-literal::
 
     -0.81054798 * IIII
     +0.17218393 * IIIZ
@@ -142,14 +142,14 @@ so:
 
 You should now directly use the ``mapper`` again, but its method is called ``.map``:
 
-.. testcode::
+.. code:: ipython3
 
    qubit_op = mapper.map(hamiltonian)
 
    for pauli, coeff in sorted(qubit_op.label_iter()):
        print(f"{coeff.real:+.8f} * {pauli}")
 
-.. testoutput::
+.. parsed-literal::
 
     -0.81054798 * IIII
     +0.17218393 * IIIZ
@@ -185,7 +185,7 @@ able to use the ``two_qubit_reduction=True`` option of the
 to the :class:`~qiskit_nature.second_q.mappers.ParityMapper`, is now directly built into said
 mapper. So if you were doing something along these lines:
 
-.. testcode::
+.. code:: ipython3
 
    from qiskit_nature.second_q.mappers import ParityMapper
 
@@ -196,7 +196,7 @@ mapper. So if you were doing something along these lines:
    for pauli, coeff in sorted(reduced_op.label_iter()):
        print(f"{coeff.real:+.8f} * {pauli}")
 
-.. testoutput::
+.. parsed-literal::
 
     -1.05237325 * II
     +0.39793742 * IZ
@@ -206,7 +206,7 @@ mapper. So if you were doing something along these lines:
 
 The equivalent code now looks like the following:
 
-.. testcode::
+.. code:: ipython3
 
    mapper = ParityMapper(num_particles=problem.num_particles)
 
@@ -215,7 +215,7 @@ The equivalent code now looks like the following:
    for pauli, coeff in sorted(reduced_op.label_iter()):
        print(f"{coeff.real:+.8f} * {pauli}")
 
-.. testoutput::
+.. parsed-literal::
 
     -1.05237325 * II
     +0.39793742 * IZ
@@ -235,7 +235,7 @@ name: :class:`~qiskit.quantum_info.analysis.z2_symmetries.Z2Symmetries`), you sh
 
 In the past, you would have enabled this like so:
 
-.. testcode::
+.. code:: ipython3
 
    mapper = JordanWignerMapper()
    converter = QubitConverter(mapper, z2symmetry_reduction="auto")
@@ -245,7 +245,7 @@ which would then later use
 sector of the Hilbert space in which the solution of your problem lies. This was only supported by
 the :class:`~qiskit_nature.second_q.problems.ElectronicStructureProblem`. Below is a quick example:
 
-.. testcode::
+.. code:: ipython3
 
    tapered_op = converter.convert(
        hamiltonian,
@@ -256,7 +256,7 @@ the :class:`~qiskit_nature.second_q.problems.ElectronicStructureProblem`. Below
    for pauli, coeff in sorted(tapered_op.label_iter()):
        print(f"{coeff.real:+.8f} * {pauli}")
 
-.. testoutput::
+.. parsed-literal::
 
     -1.04109314 * I
     +0.18093120 * X
@@ -266,7 +266,7 @@ Now, all you need to do is the use the
 :meth:`~qiskit_nature.second_q.problems.BaseProblem.get_tapered_mapper` method and provide the
 original mapper which you would like to wrap:
 
-.. testcode::
+.. code:: ipython3
 
    tapered_mapper = problem.get_tapered_mapper(mapper)
 
@@ -275,7 +275,7 @@ original mapper which you would like to wrap:
    for pauli, coeff in sorted(tapered_op.label_iter()):
        print(f"{coeff.real:+.8f} * {pauli}")
 
-.. testoutput::
+.. parsed-literal::
 
     -1.04109314 * I
     +0.18093120 * X