Prepare 0.15.0 release (#4850)

* Prepare 0.15.0 release

This commit moves the release notes into a 0.15 subdirectory to keep
them separate from development notes post-release. It also adds an
incomplete release note to add the prelude section providing the high
level overview of the release. When this merges it should be the commit
used to to tag the 0.15.0 release.

* Cleanup and fix dag deprelease notes and remove unused dag_drawer arg

This starts the processes of cleaning up and fixing the release notes by
starting with the release notes for DAGDependency and the supporting
functions. As part of that a release note for a new argument to the
dag_drawer was removed because that argument was not actually needed.
Since it was just being used to type check and it was just error prone.
This refactors the dag drawer so that the uneccessary arg is removed
and isinstance is just used.

* Avoid potential cyclic import in dag_drawer

* Start cleanup and fixing release notes

This commit starts the process of going through and cleaning up, fixing,
and rewriting the release notes for the release.

* Move and cleanup new release notes

* More release note cleanups and fixes

* More updates

* More feature releasenote updates

* Update another release note

* Start fixes of upgrade notes

* More upgrade note fixes

* More updates

* Apply suggestions from code review

Co-authored-by: Julien Gacon <[email protected]>

* Update phase estimate release note with review comments

* Move and fix new release notes

* Fix the rest of the deprecation notes

* More updates

* Update releasenotes/notes/0.15/u-and-phase-gate-e308fb4bb009014f.yaml

Co-authored-by: Julien Gacon <[email protected]>

* Finish first pass of release note fixes

* Update new release notes

* Remove out of date docstring addition

* Update 0.15.0-release-c7d85921f85f0b4d.yaml

* Move and touch up new release notes

* Move and fix new release notes

* Move new release note

* Fix whitespace in prelude

* Update releasenotes/notes/0.15/transpiler_fails_with_condition-9b4b4d66406548f0.yaml

Co-authored-by: Luciano Bello <[email protected]>

* Update rename-rescheduler-d4210a234714ed5d.yaml

* Apply suggestions from code review

* Update remove-marshmallow-validation-283fa62b3acc51e4.yaml

* Update remove-deprecated-qi-b7d5a8ca00849b02.yaml

* Apply suggestions from code review

Co-authored-by: Luciano Bello <[email protected]>

* Apply suggestions from code review

Co-authored-by: Luciano Bello <[email protected]>

Co-authored-by: Julien Gacon <[email protected]>
Co-authored-by: Ali Javadi-Abhari <[email protected]>
Co-authored-by: Luciano Bello <[email protected]>

qiskit/circuit/__init__.py

@@ -180,6 +180,8 @@
    Qubit
    ClassicalRegister
    Clbit
+   AncillaRegister
+   AncillaQubit
 
 Gates and Instructions
 ----------------------

qiskit/circuit/library/__init__.py

@@ -46,6 +46,10 @@
    HGate
    IGate
    MCPhaseGate
+   MCXGate
+   MCXGrayCode
+   MCXRecursive
+   MCXVChain
    Measure
    MSGate
    PhaseGate

qiskit/dagcircuit/dagdependency.py

@@ -446,7 +446,7 @@ def draw(self, scale=0.7, filename=None, style='color'):
         """
         from qiskit.visualization.dag_visualization import dag_drawer
         return dag_drawer(dag=self, scale=scale, filename=filename,
-                          style=style, category='dependency')
+                          style=style)
 
 
 def merge_no_duplicates(*iterables):

qiskit/visualization/dag_visualization.py

@@ -33,7 +33,7 @@
     HAS_PIL = False
 
 
-def dag_drawer(dag, scale=0.7, filename=None, style='color', category=None):
+def dag_drawer(dag, scale=0.7, filename=None, style='color'):
     """Plot the directed acyclic graph (dag) to represent operation dependencies
     in a quantum circuit.
 
@@ -52,7 +52,6 @@ def dag_drawer(dag, scale=0.7, filename=None, style='color', category=None):
         filename (str): file path to save image to (format inferred from name)
         style (str): 'plain': B&W graph
                      'color' (default): color input/output/op nodes
-        category (str): 'dependency' for drawing DAG dependency
 
     Returns:
         PIL.Image: if in Jupyter notebook and not saving to file,
@@ -87,7 +86,11 @@ def dag_drawer(dag, scale=0.7, filename=None, style='color', category=None):
     except ImportError:
         raise ImportError("dag_drawer requires pydot. "
                           "Run 'pip install pydot'.")
-    if category is None:
+    # NOTE: use type str checking to avoid potential cyclical import
+    # the two tradeoffs ere that it will not handle subclasses and it is
+    # slower (which doesn't matter for a visualization function)
+    type_str = str(type(dag))
+    if 'dagcircuit.DAGDependency' in type_str:
         G = dag.to_networkx()
         G.graph['dpi'] = 100 * scale
 
@@ -96,25 +99,28 @@ def dag_drawer(dag, scale=0.7, filename=None, style='color', category=None):
         elif style == 'color':
             for node in G.nodes:
                 n = G.nodes[node]
-                n['label'] = node.name
-                if node.type == 'op':
+                n['label'] = str(node.node_id) + ': ' + node.name
+                if node.name == 'measure':
                     n['color'] = 'blue'
                     n['style'] = 'filled'
                     n['fillcolor'] = 'lightblue'
-                if node.type == 'in':
+                if node.name == 'barrier':
                     n['color'] = 'black'
                     n['style'] = 'filled'
                     n['fillcolor'] = 'green'
-                if node.type == 'out':
+                if node.name == 'snapshot':
                     n['color'] = 'black'
                     n['style'] = 'filled'
                     n['fillcolor'] = 'red'
-            for e in G.edges(data=True):
-                e[2]['label'] = e[2]['name']
+                if node.condition:
+                    n['label'] = str(node.node_id) + ': ' + node.name + ' (conditional)'
+                    n['color'] = 'black'
+                    n['style'] = 'filled'
+                    n['fillcolor'] = 'lightgreen'
         else:
             raise VisualizationError("Unrecognized style for the dag_drawer.")
 
-    elif category == 'dependency':
+    else:
         G = dag.to_networkx()
         G.graph['dpi'] = 100 * scale
 
@@ -123,28 +129,23 @@ def dag_drawer(dag, scale=0.7, filename=None, style='color', category=None):
         elif style == 'color':
             for node in G.nodes:
                 n = G.nodes[node]
-                n['label'] = str(node.node_id) + ': ' + node.name
-                if node.name == 'measure':
+                n['label'] = node.name
+                if node.type == 'op':
                     n['color'] = 'blue'
                     n['style'] = 'filled'
                     n['fillcolor'] = 'lightblue'
-                if node.name == 'barrier':
+                if node.type == 'in':
                     n['color'] = 'black'
                     n['style'] = 'filled'
                     n['fillcolor'] = 'green'
-                if node.name == 'snapshot':
+                if node.type == 'out':
                     n['color'] = 'black'
                     n['style'] = 'filled'
                     n['fillcolor'] = 'red'
-                if node.condition:
-                    n['label'] = str(node.node_id) + ': ' + node.name + ' (conditional)'
-                    n['color'] = 'black'
-                    n['style'] = 'filled'
-                    n['fillcolor'] = 'lightgreen'
+            for e in G.edges(data=True):
+                e[2]['label'] = e[2]['name']
         else:
             raise VisualizationError("Unrecognized style for the dag_drawer.")
-    else:
-        raise VisualizationError("Unrecognized category of DAG")
 
     dot = to_pydot(G)
 

releasenotes/notes/0.15/0.15.0-release-c7d85921f85f0b4d.yaml

@@ -0,0 +1,14 @@
+---
+prelude: |
+    The 0.15.0 release includes several new features and bug fixes. Some
+    highlights for this release are:
+
+    This release includes the introduction of arbitrary
+    basis translation to the transpiler. This includes support for directly
+    targeting a broader range of device basis sets, e.g. backends
+    implementing RZ, RY, RZ, CZ or iSwap gates.
+
+    The :class:`~qiskit.circuits.QuantumCircuit` class now tracks global
+    phase. This means controlling a circuit which has global phase now
+    correctly adds a relative phase, and gate matrix definitions are now
+    exact rather than equal up to a global phase.

releasenotes/notes/0.15/4500-barrier-counted-as-non-local-gate-6cb31d63a9052632.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    The :class:`qiskit.circuit.QuantumCircuit` method
+    :attr:`~qiskit.circuit.QuantumCircuit.num_nonlocal_gates` previously
+    included multi-qubit :class:`qiskit.circuit.Instruction` objects
+    (for example, :class:`~qiskit.circuit.library.Barrier`) in its count of
+    non-local gates. This has been corrected so that only non-local
+    :class:`~qiskit.circuit.Gate` objects are counted.
+    Fixes `#4500 <https://github.com/Qiskit/qiskit-terra/issues/4500>`__

releasenotes/notes/0.15/4524-MCXVChain-gate-being-incorrectly-assembled-as-MCX-gate-df73b216e9777ecf.yaml

@@ -0,0 +1,12 @@
+---
+upgrade:
+  - |
+    Implementations of the multi-controlled X Gate (
+    :class:`~qiskit.circuit.library.MCXGrayCode`,
+    :class:`~qiskit.circuit.library.MCXRecursive`, and
+    :class:`~qiskit.circuit.library.MCXVChain`) have had their ``name``
+    properties changed to more accurately describe their
+    implementation: ``mcx_gray``, ``mcx_recursive``, and
+    ``mcx_vchain`` respectively. Previously, these gates shared the
+    name ``mcx`` with :class:`~qiskit.circuit.library.MCXGate`, which caused
+    these gates to be incorrectly transpiled and simulated.

releasenotes/notes/0.15/4573-Open-ControlledGates-not-marked-equivalent-729bc971c897ede3.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    :class:`~qiskit.circuit.ControlledGate` instances with a set
+    ``ctrl_state`` were in some cases not being evaluated as equal, even if the
+    compared gates were equivalent. This has been resolved so that
+    Fixes `#4573 <https://github.com/Qiskit/qiskit-terra/issues/4573>`__

releasenotes/notes/0.15/Add-canonical-form-47e0466ed57640f3.yaml

@@ -0,0 +1,35 @@
+---
+features:
+  - |
+    A new DAG class :class:`qiskit.dagcircuit.DAGDependency` for representing
+    the dependency form of circuit, In this DAG, the nodes are
+    operations (gates, measure, barrier, etc...) and the edges corresponds to
+    non-commutation between two operations.
+  - |
+    Four new functions are added to :mod:`qiskit.converters` for converting back and
+    forth to :class:`~qiskit.dagcircuit.DAGDependency`. These functions are:
+
+    * :func:`~qiskit.converters.circuit_to_dagdependency` to convert
+      from a :class:`~qiskit.circuit.QuantumCircuit` object to a
+      :class:`~qiskit.dagcircuit.DAGDependency` object.
+    * :func:`~qiskit.converters.dagdependency_to_circuit` to convert from a
+      :class:`~qiskit.dagcircuit.DAGDependency` object to a
+      :class:`~qiskit.circuit.QuantumCircuit` object.
+    * :func:`~qiskit.converters.dag_to_dagdependency` to convert from
+      a :class:`~qiskit.dagcircuit.DAGCircuit` object to a
+      :class:`~qiskit.dagcircuit.DAGDependency` object.
+    * :func:`~qiskit.converters.dagdependency_to_ciruit` to convert from
+      a :class:`~qiskit.dagcircuit.DAGDependency` object to a
+      :class:`~qiskit.dagcircuit.DAGCircuit` object.
+
+    For example::
+    
+      from qiskit.converters.dagdependency_to_circuit import dagdependency_to_circuit
+      from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
+
+      circuit_in = QuantumCircuit(2)
+      circuit_in.h(qr[0])
+      circuit_in.h(qr[1])
+
+      dag_dependency = circuit_to_dagdependency(circuit_in)
+      circuit_out = dagdepency_to_circuit(dag_dependency)

releasenotes/notes/0.15/add-basistranslator-pass-d5e7de69ab9f20a1.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    Two new transpiler passes have been added to :mod:`qiskit.transpiler.passes`
+    The first, :class:`~qiskit.transpiler.passes.UnrollCustomDefinitions`,
+    unrolls all instructions in the
+    circuit according to their :attr:`~qiskit.circuit.Instruction.definition`
+    property, stopping when reaching either the specified ``basis_gates``
+    or a set of gates in the provided
+    :class:`~qiskit.circuit.EquivalenceLibrary`. The second,
+    :class:`~qiskit.transpiler.passes.BasisTranslator`, uses the set of
+    translations in the provided :class:`~qiskit.circuit.EquivalenceLibrary` to
+    re-write circuit instructions in a specified basis.

releasenotes/notes/0.15/add-basistranslator-to-default-levels-1c0de250f8ca4a59.yaml

@@ -0,0 +1,28 @@
+---
+features:
+  - |
+    A new ``translation_method`` keyword argument has been added to
+    :func:`~qiskit.compiler.transpile` to allow selection of the method to be
+    used for translating circuits to the available device gates. For example,
+    ``transpile(circ, backend, translation_method='translator')``. Valid
+    choices are:
+
+    * ``'unroller'``: to use the :class:`~qiskit.transpiler.passes.Unroller`
+      pass
+    * ``'translator'``: to use the
+      :class:`~qiskit.transpiler.passes.BasisTranslator` pass.
+    * ``'synthesis'``: to use the
+      :class:`~qiskit.transpiler.passes.UnitarySynthesis` pass.
+
+    The  default value is ``'translator'``.
+upgrade:
+  - |
+    By default the preset passmanagers in
+    :mod:`qiskit.transpiler.preset_passmanagers` are using
+    :class:`~qiskit.transpiler.passes.UnrollCustomDefinitions` and
+    :class:`~qiskit.transpiler.passes.BasisTranslator` to handle basis changing
+    instead of the previous default :class:`~qiskit.transpiler.passes.Unroller`.
+    This was done because the new passes are more flexible and allow targeting
+    any basis set, however the output may differ. To use the previous default
+    you can set the ``translation_method`` kwarg on
+    :func:`~qiskit.compiler.transpile` to ``'unroller'``.

releasenotes/notes/0.15/add-counts-class-7c75bd94d12a161a.yaml

@@ -0,0 +1,17 @@
+---
+features:
+  - |
+    A new class for handling counts result data, :class:`qiskit.result.Counts`,
+    has been added. This class is a subclass of ``dict`` and can be interacted
+    with like any other dictionary. But, it includes helper methods and
+    attributes for dealing with counts results from experiments and also
+    handles post processing and formatting of binary strings at object
+    initialization. A :class:`~qiskit.result.Counts`  object can be created by
+    passing a dictionary  of counts with the keys being either integers,
+    hexadecimal strings of the form ``'0x4a'``,  binary strings of the form
+    ``'0b1101'``, a bit string formatted across register and memory slots
+    (ie ``'00 10'``), or a dit string. For example::
+
+      from qiskit.result import Counts
+
+      counts = Counts({"0x0': 1, '0x1', 3, '0x2': 1020})

releasenotes/notes/0.15/add-init-qubits-option-ea1844f88fcddcf6.yaml

@@ -0,0 +1,13 @@
+---
+features:
+  - |
+    A new kwarg for ``init_qubits`` has been added to
+    :func:`~qiskit.compiler.assemble` and :func:`~qiskit.execute.execute`.
+    For backends that support this feature ``init_qubits`` can be used to
+    control whether the backend executing the circuits inserts any
+    initialization sequences at the start of each shot. By default this is set
+    to ``True`` meaning that all qubits can assumed to be in the ground state
+    at the start of each shot. However, when ``init_qubits`` is  set to
+    ``False`` qubits will be uninitialized at the start of each
+    experiment and between shots. Note, that the backend running the circuits
+    has to support this feature for this flag to have any effect.

releasenotes/notes/0.15/add-rep-delay-c97d5aa8fc9696da.yaml

@@ -0,0 +1,31 @@
+---
+features:
+  - |
+    A new kwarg ``rep_delay`` has been added to
+    :func:`qiskit.compiler.assemble`, :func:`qiskit.execute.execute`, and the
+    constructor for :class:`~qiskit.qobj.PulseQobjtConfig`.qiskit
+    This new kwarg is used to denotes the time between program executions. It
+    must be chosen from the list of valid values set as the
+    ``rep_delays`` from a backend's
+    :class:`~qiskit.providers.models.PulseBackendConfiguration` object which
+    can be accessed as ``backend.configuration().rep_delays``).
+
+    The ``rep_delay`` kwarg will only work on backends which allow for dynamic
+    repetition time. This will also be indicated in the
+    :class:`~qiskit.providers.models.PulseBackendConfiguration` object for a
+    backend as the ``dynamic_reprate_enabled`` attribute. If
+    ``dynamic_reprate_enabled`` is ``False`` then the ``rep_time`` value
+    specified for :func:`qiskit.compiler.assemble`,
+    :func:`qiskit.execute.execute`, or the constructor for
+    :class:`~qiskit.qobj.PulseQobjtConfig` will be used rather than
+    ``rep_delay``. ``rep_time`` only allows users to specify the duration of a
+    program, rather than the delay between programs.
+  - |
+    The ``qobj_schema.json`` JSON Schema file in :mod:`qiskit.schemas` has
+    been updated to include the ``rep_delay`` as an optional configuration
+    property for pulse qobjs.
+  - |
+    The ``backend_configuration_schema.json`` JSON Schema file in
+    mod:`qiskit.schemas` has been updated to include ``rep_delay_range`` and
+    ``default_rep_delay`` as optional properties for a pulse backend
+    configuration.

releasenotes/notes/0.15/add_quantumcircuit_phase-5006d1e930348d2e.yaml

@@ -0,0 +1,32 @@
+features:
+  - |
+    A new attribute, :attr:`~qiskit.circuit.QuantumCircuit.global_phase`,
+    which is is used for tracking the global phase has been added to the
+    :class:`qiskit.circuit.QuantumCircuit` class. For example::
+
+      import math
+
+      from qiskit import QuantumCircuit
+
+      circ = QuantumCircuit(1, global_phase=math.pi)
+      circ.u1(0)
+
+    The global phase may also be changed or queried with
+    ``circ.global_phase`` in the above example. In either case the setting is
+    in radians. If the circuit is converted to an instruction or gate the
+    global phase is represented by two single qubit rotations on the first
+    qubit.
+
+    This allows for other methods and functions which consume a
+    :class:`~qiskit.circuit.QuantumCircuit` object to take global phase into
+    account. For example. with the
+    :attr:`~qiskit.circuit.QuantumCircuit.global_phase`
+    attribute the :meth:`~qiskit.circuit.Gate.to_matrix` method for a gate
+    can now exactly correspond to its decompositions instead of
+    just up to a global phase.
+
+    The same attribute has also been added to the
+    :class:`~qiskit.dagcircuit.DAGCircuit` class so that global phase
+    can be tracked when converting between
+    :class:`~qiskit.circuit.QuantumCircuit` and
+    :class:`~qiskit.dagcircuit.DAGCircuit`.

releasenotes/notes/0.15/allowIntegerforQuantumRegisterSize-2e9a6cc033bc962e.yaml

@@ -0,0 +1,12 @@
+---
+fixes:
+  - |
+    When accessing a bit from a
+    :class:`qiskit.circuit.QuantumRegister` or
+    :class:`qiskit.circuit.ClassicalRegister` by index when using numpy
+    `integer types` <https://numpy.org/doc/stable/user/basics.types.html>`__
+    would previously raise a ``CircuitError`` exception. This has been
+    resolved so numpy types can be used in addition to Python's built-in
+    ``int`` type.
+    Fixes `#3929 <https://github.com/Qiskit/qiskit-terra/issues/3929>`__.
+    

releasenotes/notes/0.15/ancilla-qubit-cdf5fb28373b8553.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Two new classes, :class:`~qiskit.circuit.AncillaRegister` and
+    :class:`~qiskit.circuit.AncillaQubit` have been added to the
+    :mod:`qiskit.circuit` module. These are subclasses of
+    :class:`~qiskit.circuit.QuantumRegister` and :class:`~qiskit.circuit.Qubit`
+    respectively and enable marking qubits being ancillas. This will allow
+    these qubits to be re-used in larger circuits and algorithms.

releasenotes/notes/0.15/bugfix-set-frequency-29608d213a8cbece.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    The SI unit use for constructing :py:class:`qiskit.pulse.SetFrequency`
+    objects is in Hz, but when a :class:`~qiskit.qobj.PulseQobjInstruction`
+    object is created from a :py:class:`~qiskit.pulse.SetFrequency` instance
+    it needs to be converted to GHz. This conversion was missing from previous
+    releases and has been fixed.

releasenotes/notes/0.15/change-pulse_lib-to-library-f8e76ff3136128ec.yaml

@@ -0,0 +1,6 @@
+---
+deprecations:
+  - |
+    The ``qiskit.pulse.pulse_lib`` module has been deprecated and will be
+    removed in a future release. It has been renamed to
+    :py:mod:`qiskit.pulse.library` which should be used instead.