Prepare 0.21.1 release (#8398)

* Prepare 0.21.1 release

This commit prepares for the 0.21.1 release by bumping the version
strings to reflect the new version. This is just a bugfix release that
fixes bugs since the 0.21.0 release.

* Update release notes

* Fix typo

* Update releasenotes/notes/decompose-fix-993f7242eaa69407.yaml

Co-authored-by: Kevin Hartman <kevin@hart.mn>

* Move stray 0.21.0 release note to a 0.21.0 release note file

Co-authored-by: Kevin Hartman <kevin@hart.mn>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "qiskit-terra"
-version = "0.21.0"
+version = "0.21.1"
 edition = "2018"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

docs/conf.py

@@ -23,7 +23,7 @@
 # The short X.Y version
 version = "0.21"
 # The full version, including alpha/beta/rc tags
-release = "0.21.0"
+release = "0.21.1"
 
 extensions = [
     "sphinx.ext.napoleon",

qiskit/VERSION.txt

@@ -1 +1 @@
-0.21.0
+0.21.1

releasenotes/notes/0.21/release-0.21.0-4a6c079c6301bde6.yaml

@@ -22,3 +22,27 @@ prelude: |
   Additionally, the transpiler has been improved to enable better quality
   outputs. This includes the introduction of new passes such as
   :class:`~.VF2PostLayout` and :class:`~.ToqmSwap`.
+upgrade:
+  - |
+    The preset pass managers generated by :func:`~.level_1_pass_manager`,
+    :func:`~.level_2_pass_manager`, and :func:`~.level_3_pass_manager` and used
+    by the :func:`~.transpile` function's ``optimization_level`` argument at
+    1, 2, and 3 respectively no longer set a hard time limit on the
+    :class:`~.VF2Layout` transpiler pass. This means that the pass will no
+    longer stop trying to find a better alternative perfect layout up until a
+    fixed time limit (100ms for level 1, 10 sec for level 2, and 60 sec for
+    level 3) as doing this limited the reproducibility of compilation when a
+    perfect layout was available. This means that the output when using the pass
+    might be different than before, although in all cases it would only change
+    if a lower noise set of qubits can be found over the previous output. If
+    you wish to retain the previous behavior you can create a custom
+    :class:`~.PassManager` that sets the ``time_limit`` argument on the
+    constructor for the :class:`~VF2Layout` pass.
+fixes:
+  - |
+    Fixed an issue with reproducibility of the :func:`~.transpile` function
+    when running with ``optimization_level`` 1, 2, and 3. Previously, under
+    some conditions when there were multiple perfect layouts (a layout that
+    doesn't require any SWAP gates) available the selected layout and output
+    circuit could vary regardless of whether the ``seed_transpiler`` argument
+    was set.

releasenotes/notes/decompose-fix-993f7242eaa69407.yaml

@@ -1,4 +1,7 @@
 ---
 fixes:
-  - Fixed a bug in :meth:`.QuantumCircuit.decompose` that caused the
-    `gates_to_decompose` argument to be handled incorrectly.
+  - Fixed an issue in :meth:`.QuantumCircuit.decompose` method when
+    passing in a list of ``Gate`` classes for the ``gates_to_decompose``
+    argument. If any gates in the circuit had a label set this argument
+    wouldn't be handled correctly and caused the output decomposition to
+    incorrectly skip gates explicitly in the ``gates_to_decompose`` list.

releasenotes/notes/fix-pulse-limit_amplitude-72b8b501710fe3aa.yaml

@@ -1,7 +1,9 @@
 ---
 fixes:
   - |
-    A bug that ``limit_amplitude`` set to an individual symbolic pulse or waveform instance
-    is not properly reflected to the parameter validation has been fixed.
-    In addition, QPY schedule ``dump`` has been fixed to save ``limit_amplitude`` value
-    tied to the instance, rather than saving the global class variable.
+    Fixed an issue where the ``limit_amplitude`` argument on an individual
+    :class:`~.SymbolicPulse` or :class:`~.Waveform` instance
+    was not properly reflected by parameter validation. In addition, QPY
+    schedule :func:`~qiskit.qpy.dump` has been fixed to correctly
+    store the ``limit_amplitude`` value tied to the instance, rather than
+    saving the global class variable.

releasenotes/notes/fix-zzmap-pairwise-5653395849fec454.yaml

@@ -2,14 +2,17 @@
 fixes:
   - |
     Fix the pairwise entanglement structure for :class:`~.NLocal` circuits.
-    This led to a bug in the :class:`~.ZZFeatureMap`, where using `entanglement="pairwise"`
-    raised an error. Now it correctly produces the desired feature map::
+    This led to a bug in the :class:`~.ZZFeatureMap`, where using
+    ``entanglement="pairwise"`` raised an error. Now it correctly produces the
+    desired feature map::
 
       from qiskit.circuit.library import ZZFeatureMap
       encoding = ZZFeatureMap(4, entanglement="pairwise", reps=1)
       print(encoding.decompose().draw())
 
-    The above prints::
+    The above prints:
+
+    .. parsed-literal::
 
            ┌───┐┌─────────────┐
       q_0: ┤ H ├┤ P(2.0*x[0]) ├──■────────────────────────────────────■────────────────────────────────────────────

releasenotes/notes/global-phase-ucgate-cd61355e314a3e64.yaml

@@ -1,4 +1,4 @@
 ---
 fixes:
   - |
-    Fixed a global phase bug in :class:`~.UCGate`.
+    Fixed an issue in handling the global phase of the :class:`~.UCGate` class.

setup.py

@@ -51,7 +51,7 @@
 
 setup(
     name="qiskit-terra",
-    version="0.21.0",
+    version="0.21.1",
     description="Software for developing quantum computing programs",
     long_description=README,
     long_description_content_type="text/markdown",