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---
title: Qiskit 0.45 release notes
description: Changes made in Qiskit 0.45
in_page_toc_max_heading_level: 3
---
<span id="release-notes" />
<span id="id1" />
# Qiskit 0.45 release notes
This page contains the release notes for Qiskit 0.45, the first release after the legacy “elements” structure was completely removed. For all release notes, including those stretching back through the old “meta-package” structure of Qiskit, see [Release notes](/api/qiskit/release-notes). For a table of meta-package versions, see the [Qiskit 0.44 release notes](/api/qiskit/release-notes/0.44).
<span id="relnotes-0-45-0" />
<span id="id2" />
## 0.45.3
<span id="relnotes-0-45-3-stable-0-45-prelude" />
### Prelude
Qiskit 0.45.3 is a point release with no code changes other than to raise an [`ImportError`](https://docs.python.org/3/library/exceptions.html#ImportError "(in Python v3.12)") if it detects it has been installed in an invalid environment with Qiskit >=1.0.
Please read [our migration guide about the new packaging](https://qisk.it/1-0-packaging-migration) for help on errors, preparing for Qiskit 1.0, and more detailed background information.
<Admonition title="Note" type="note">
Qiskit 1.0 is due to release approximately two weeks after Qiskit 0.45.3, on the 15th of February 2024, and might not yet be available when you read this message. This change is being made proactively.
</Admonition>
The packaging structure of Qiskit is changing in Qiskit 1.0, and unfortunately the changed requirements cannot be fully communicated to `pip`, especially if `pip install --upgrade` commands are run after the environment has been initially configured. All versions of Qiskit prior to 1.0 (including this one) have an installation conflict with Qiskit 1.0 that `pip` will not resolve.
If `import qiskit` raises an [`ImportError`](https://docs.python.org/3/library/exceptions.html#ImportError "(in Python v3.12)") for you, your environment is in an invalid state, and versions of Qiskit 0.45/0.46 and 1.0 are both reachable, which will result in subtly broken code. You will need to create a new virtual environment, and ensure that *only* one of the two versions are installed. In particular, if you are intending to install Qiskit 1.0, you must have no packages that depend on `qiskit-terra` installed; these packages are incompatible with Qiskit 1.0 and must be updated. If you are intending to install Qiskit 0.45 or 0.46, you must ensure that you have nothing attempting to install `qiskit>=1.0`.
If you develop a library based on Qiskit and you still have a dependency on `qiskit-terra`, you should urgently release a new package that depends only on `qiskit`. Since version 0.44, the `qiskit` package contained only the `qiskit-terra` compiler core (the component that is now simply called “Qiskit”), so if your minimum version is `0.44`, you can safely switch a `qiskit-terra>=0.44` dependency to `qiskit>=0.44` with no change in what will be installed. For more detail and recommendations for testing and preparation, see the [section for developers of the migration guide](https://qisk.it/1-0-packaging-migration#for-developers).
<span id="relnotes-0-45-2-stable-0-45" />
<span id="id3" />
## 0.45.2
<span id="relnotes-0-45-2-stable-0-45-prelude" />
<span id="id4" />
### Prelude
Qiskit 0.45.2 is a small patch release, fixing several bugs found in the 0.45 release series.
<span id="relnotes-0-45-2-stable-0-45-bug-fixes" />
### Bug Fixes
* Calling [`copy()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#copy "qiskit.circuit.QuantumCircuit.copy") or [`copy_empty_like()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#copy_empty_like "qiskit.circuit.QuantumCircuit.copy_empty_like") on a `BlueprintCircuit` will now correctly propagate the [`global_phase`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#global_phase "qiskit.circuit.QuantumCircuit.global_phase") to the copy. Previously, the global phase would always be zero after the copy.
* QPY (using [`qpy.dump()`](/api/qiskit/0.45/qpy#qiskit.qpy.dump "qiskit.qpy.dump") and [`qpy.load()`](/api/qiskit/0.45/qpy#qiskit.qpy.load "qiskit.qpy.load")) will now correctly serialize and deserialize quantum circuits with Clifford operators ([`Clifford`](/api/qiskit/0.45/qiskit.quantum_info.Clifford "qiskit.quantum_info.Clifford")).
* Fixed an issue in the `mpl` circuit drawer where the text would print beyond the end of the box for a [`SwitchCaseOp`](/api/qiskit/0.45/qiskit.circuit.SwitchCaseOp "qiskit.circuit.SwitchCaseOp") if the default case was empty.
* The qubit-argument broadcasting of [`QuantumCircuit.delay()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#delay "qiskit.circuit.QuantumCircuit.delay") now correctly produces individual [`Delay`](/api/qiskit/0.45/qiskit.circuit.Delay "qiskit.circuit.Delay") instructions for each qubit, as intended. Previously, when given certain iterables (such as [`set`](https://docs.python.org/3/library/stdtypes.html#set "(in Python v3.12)")s), it would instead silently produce an invalid circuit that might fail in unusual locations.
* Fixed a bug that results in an error when a user tries to load .calibration data of a gate in [`Target`](/api/qiskit/0.45/qiskit.transpiler.Target "qiskit.transpiler.Target") in a particular situation. This occurs when the backend reports only partial calibration data, for example referencing a waveform pulse in a command definition but not including that waveform pulse in the pulse library. In this situation, the Qiskit pulse object cannot be built, resulting in a failure to build the pulse schedule for the calibration. Now when calibration data is incomplete the [`Target`](/api/qiskit/0.45/qiskit.transpiler.Target "qiskit.transpiler.Target") treats it as equivalent to no calibration being reported at all and does not raise an exception.
* Fixed an issue with the [`Optimize1qGatesDecomposition`](/api/qiskit/0.45/qiskit.transpiler.passes.Optimize1qGatesDecomposition "qiskit.transpiler.passes.Optimize1qGatesDecomposition") transpiler pass where it would potentially resynthesize a single ideal (meaning the error rate is `0.0`) gate which was present in the [`Target`](/api/qiskit/0.45/qiskit.transpiler.Target "qiskit.transpiler.Target"). This is now fixed so the pass [`Optimize1qGatesDecomposition`](/api/qiskit/0.45/qiskit.transpiler.passes.Optimize1qGatesDecomposition "qiskit.transpiler.passes.Optimize1qGatesDecomposition") will defer to the circuit’s gate if the error rate (which includes number of gates) are the same. Fixed [#10568](https://github.com/Qiskit/qiskit/issues/10568)
* Fixed an issue with the `OptimizeSwapBeforeMeasure` pass where it would incorrectly optimize circuits involving swap and measure instructions. This commit fixes the bug by changing [`DAGCircuit.successors()`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit#successors "qiskit.dagcircuit.DAGCircuit.successors") to [`DAGCircuit.descendants()`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit#descendants "qiskit.dagcircuit.DAGCircuit.descendants"). Also, added a couple of extra tests to ensure that the bug is fixed. For example:
```python
from qiskit import QuantumCircuit
from qiskit.transpiler.passes import OptimizeSwapBeforeMeasure
pass_ = OptimizeSwapBeforeMeasure()
qc = QuantumCircuit(2, 1)
qc.swap(0, 1)
qc.measure(0, 0)
qc.measure(0, 0)
print(qc.draw())
print(pass_(qc).draw())
```
would previously print:
```python
┌─┐┌─┐
q_0: ─X─┤M├┤M├
│ └╥┘└╥┘
q_1: ─X──╫──╫─
║ ║
c: 1/════╩══╩═
0 0
┌─┐
q_0: ┤M├───
└╥┘┌─┐
q_1: ─╫─┤M├
║ └╥┘
c: 1/═╩══╩═
0 0
```
and now the second ciruit is correctly optimized to:
```python
q_0: ──────
┌─┐┌─┐
q_1: ┤M├┤M├
└╥┘└╥┘
c: 1/═╩══╩═
0 0
```
* Fix a bug in the [`StabilizerState`](/api/qiskit/0.45/qiskit.quantum_info.StabilizerState "qiskit.quantum_info.StabilizerState") string representation.
<span id="relnotes-0-45-1-stable-0-45" />
<span id="id5" />
## 0.45.1
<span id="relnotes-0-45-1-stable-0-45-prelude" />
<span id="id6" />
### Prelude
Qiskit Terra 0.45.1 is a small patch release, fixing several bugs found in the 0.45 release series. It is also the first release to have official support for Python 3.12. The 0.45.1 release supports Python 3.8, 3.9, 3.10, 3.11, and 3.12.
<span id="relnotes-0-45-1-stable-0-45-new-features" />
### New Features
* Added support for using Qiskit with Python 3.12. As of this release Qiskit supports running with Python versions 3.8, 3.9, 3.10, 3.11, and 3.12.
<span id="relnotes-0-45-1-stable-0-45-bug-fixes" />
<span id="id7" />
### Bug Fixes
* [`QuantumCircuit.barrier()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#barrier "qiskit.circuit.QuantumCircuit.barrier") will now generate correct output when given a [`set`](https://docs.python.org/3/library/stdtypes.html#set "(in Python v3.12)") as one of its inputs. Previously, it would append an invalid operation onto the circuit, though in practice this usually would not cause observable problems. Fixed [#11208](https://github.com/Qiskit/qiskit/issues/11208)
* The property [`Instruction.condition_bits`](/api/qiskit/0.45/qiskit.circuit.Instruction#condition_bits "qiskit.circuit.Instruction.condition_bits") will now correctly handle runtime classical expressions ([`qiskit.circuit.classical`](/api/qiskit/0.45/circuit_classical#module-qiskit.circuit.classical "qiskit.circuit.classical")).
* Fixed the [`hash()`](https://docs.python.org/3/library/functions.html#hash "(in Python v3.12)") of Qiskit Pulse `Channel` objects (such as [`DriveChannel`](/api/qiskit/0.45/qiskit.pulse.channels.DriveChannel "qiskit.pulse.channels.DriveChannel")) in cases where the channel was transferred from one Python process to another that used a different hash seed.
* Conditioned custom gates imported from OpenQASM 2 will now correctly retain their conditions when pickled and deep-copied. Previously, any conditional custom gate (defined by a `gate` statement in an OpenQASM 2 file) would lose its condition when copied or pickled.
* Fixed QPY deserialization of the [`StatePreparation`](/api/qiskit/0.45/qiskit.circuit.library.StatePreparation "qiskit.circuit.library.StatePreparation") and [`Initialize`](/api/qiskit/0.45/qiskit.circuit.library.Initialize "qiskit.circuit.library.Initialize") circuit instructions with string and integer parameters (as opposed to an explicit statevector, which was already working). Fixed [#11158](https://github.com/Qiskit/qiskit/issues/11158).
* Fixed a bug in [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") where it would fail to add the register information to the [`Layout`](/api/qiskit/0.45/qiskit.transpiler.Layout "qiskit.transpiler.Layout") object used for [`TranspileLayout.initial_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#initial_layout "qiskit.transpiler.TranspileLayout.initial_layout"). This affected circuit visualization with [`QuantumCircuit.draw()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#draw "qiskit.circuit.QuantumCircuit.draw") and [`circuit_drawer()`](/api/qiskit/0.45/qiskit.visualization.circuit_drawer "qiskit.visualization.circuit_drawer") after transpilation which would show a virtual qubit label of the form `Qubit[QuantumRegister(6, 'q', 0)]` rather than the expected virtual qubit label using the register name (e.g. `q0`). Fixed [#11038](https://github.com/Qiskit/qiskit/issues/11038)
* Fixed an issue with [`qpy.dump()`](/api/qiskit/0.45/qpy#qiskit.qpy.dump "qiskit.qpy.dump") which would cause the function to potentially ignore the value of `use_symengine` when serializing a [`ScheduleBlock`](/api/qiskit/0.45/qiskit.pulse.ScheduleBlock "qiskit.pulse.ScheduleBlock") object. This would result in an invalid QPY payload being generated as it would report it was using symengine for symbolic expressions but actually contain sympy serialized data.
* Fixed a bug which caused [`UnitaryOverlap`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryOverlap "qiskit.circuit.library.UnitaryOverlap") to error upon initialization if given an input circuit containing a barrier.
<span id="relnotes-0-45-0-stable-0-45" />
<span id="id8" />
## 0.45.0
<span id="relnotes-0-45-0-stable-0-45-prelude" />
<span id="id9" />
### Prelude
Qiskit 0.45.0 is the last feature release before 1.0. It prepares the ground for the API changes we are planning for our first major version release, including many removals of previously deprecated functionality as well as a series of new deprecations.
<Admonition title="Note" type="note">
If your project depends on Qiskit, it may rely on functionality that will no longer be supported in Qiskit 1.0. For this reason, we recommend that you proactively cap your supported version to `<1.0`.
</Admonition>
Some feature highlights of Qiskit 0.45.0 are:
* Starting in this release, all unparametrized gates in the Qiskit standard circuit library are now **singletons**. By default, these gates share a single instance in memory, so once a gate of a specific type, let’s say [`XGate`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate"), is instantiated, any subsequent instances of [`XGate`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate") will be a reference to the first one. This results in a reduced memory usage and construction overhead when using multiple gates of the same type in a circuit. To realize this feature, new base classes have been introduced: [`SingletonInstruction`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonInstruction "qiskit.circuit.singleton.SingletonInstruction") and [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate"). See feature notes for more details.
* We have added a new **generic pass manager interface** that can be found in the new [`qiskit.passmanager`](/api/qiskit/0.45/passmanager#module-qiskit.passmanager "qiskit.passmanager") module. This is a generalization of the pass manager that was used to build the Qiskit transpiler, and it introduces a generic framework to enable users to create new pass managers that use different intermediate representations (IRs). The module includes a generic pass manager base class, flow controllers, and the necessary infrastructure to manage the execution of pass manager tasks. The new interface was used to rebuild the existing pass manager in the [`qiskit.transpiler`](/api/qiskit/0.45/transpiler#module-qiskit.transpiler "qiskit.transpiler") module, cleaning up technical debt in the code, and improving usability and performance. See feature and upgrade notes for more details.
* 0.45.0 allows users to better interact with the **layout permutations** performed by the transpiler. The data contained in the [`TranspileLayout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout") class is now more accessible through a series of new methods and attributes. And a new [`SparsePauliOp.apply_layout()`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp#apply_layout "qiskit.quantum_info.SparsePauliOp.apply_layout") method allows to apply a specific layout permutation to a [`SparsePauliOp`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp "qiskit.quantum_info.SparsePauliOp") observable that was built for an input circuit to the transpiler. See feature notes for more details.
* Finally, we have introduced **annotated operations** with the new [`AnnotatedOperation`](/api/qiskit/0.45/qiskit.circuit.AnnotatedOperation "qiskit.circuit.AnnotatedOperation") class, which allows to formulate complex circuit instructions as a base instruction with a set of modifiers. For example, instead of a specific operation type that implements the controlled inverse of a [`RXGate`](/api/qiskit/0.45/qiskit.circuit.library.RXGate "qiskit.circuit.library.RXGate"), we can now use an annotated [`RXGate`](/api/qiskit/0.45/qiskit.circuit.library.RXGate "qiskit.circuit.library.RXGate") with inverse and control attributes. See feature notes for more details.
<span id="relnotes-0-45-0-stable-0-45-circuits-features" />
### Circuits Features
* Added a new class [`AnnotatedOperation`](/api/qiskit/0.45/qiskit.circuit.AnnotatedOperation "qiskit.circuit.AnnotatedOperation") that is a subclass of [`Operation`](/api/qiskit/0.45/qiskit.circuit.Operation "qiskit.circuit.Operation") and represents some “base operation” modified by a list of “modifiers”. The base operation is of type [`Operation`](/api/qiskit/0.45/qiskit.circuit.Operation "qiskit.circuit.Operation") and the currently supported modifiers are of types [`InverseModifier`](/api/qiskit/0.45/qiskit.circuit.InverseModifier "qiskit.circuit.InverseModifier"), [`ControlModifier`](/api/qiskit/0.45/qiskit.circuit.ControlModifier "qiskit.circuit.ControlModifier") and [`PowerModifier`](/api/qiskit/0.45/qiskit.circuit.PowerModifier "qiskit.circuit.PowerModifier"). The modifiers are applied in the order they appear in the list.
As an example:
```python
gate = AnnotatedOperation(
base_op=SGate(),
modifiers=[
InverseModifier(),
ControlModifier(1),
InverseModifier(),
PowerModifier(2),
],
)
```
is logically equivalent to `gate = SGate().inverse().control(1).inverse().power(2)`, or to:
```python
gate = AnnotatedOperation(
AnnotatedOperation(SGate(), [InverseModifier(), ControlModifier(1)]),
[InverseModifier(), PowerModifier(2)],
)
```
However, this equivalence is only logical, the internal representations are very different.
For convenience, a single modifier can be also passed directly, thus `AnnotatedGate(SGate(), [ControlModifier(1)])` is equivalent to `AnnotatedGate(SGate(), ControlModifier(1))`.
A distinguishing feature of an annotated operation is that circuit definition is not constructed when the operation is declared, and instead happens only during transpilation, specifically during the [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") transpiler pass.
An annotated operation can be also viewed as a “higher-level” or a “more abstract” object that can be added onto a quantum circuit. This enables writing transpiler optimization passes that make use of this higher-level representation, for instance removing a gate that is immediately followed by its inverse (note that this reduction might not be possible if both the gate and its inverse are first synthesized into simpler gates).
In a sense, an annotated operation can be viewed as an extension of [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate"), which also allows adding control to the base operation. In the future we are planning to replace [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate") by [`AnnotatedOperation`](/api/qiskit/0.45/qiskit.circuit.AnnotatedOperation "qiskit.circuit.AnnotatedOperation"). Similar to controlled gates, the transpiler synthesizes annotated operations before layout/routing takes place.
As of now, the annotated operations can appear only in the top-level of a quantum circuit, that is they cannot appear inside of the recursively-defined `definition` circuit. We are planning to remove this limitation later.
* Added a new option `max_num_qubits` to [`qiskit.circuit.CommutationChecker.commute()`](/api/qiskit/0.45/qiskit.circuit.CommutationChecker#commute "qiskit.circuit.CommutationChecker.commute") that specifies the maximum number of qubits to consider for the more expensive matrix multiplication-based commutativity check. This avoids trying to internally allocate arrays of size $2^N \times 2^N$. Simpler versions of commutativity check (for instance, two quantum operations commute when they are over disjoint sets of qubits) continue to work without this limit.
* Added a new argument, `check_input`, to the constructor for the [`UnitaryGate`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryGate "qiskit.circuit.library.UnitaryGate") class. This flag is used to disable the default initialization checks that input object represents a unitary matrix. This can be used to speed up the creation of [`UnitaryGate`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryGate "qiskit.circuit.library.UnitaryGate") objects if you know the input is already a unitary matrix. This new option should only be used in these cases because if it’s set to `False` and the input is not unitary this will result in an invalid `UnitaryGate` object.
* A new method [`Parameter.assign()`](/api/qiskit/0.45/qiskit.circuit.Parameter#assign "qiskit.circuit.Parameter.assign") has been added. This method primarily serves as a fast path to improve the performance of [`QuantumCircuit.assign_parameters()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#assign_parameters "qiskit.circuit.QuantumCircuit.assign_parameters") for the common case of circuits that predominantly contain “expressions” that are actually just single parameters to be assigned later.
* The performance of [`QuantumCircuit.assign_parameters()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#assign_parameters "qiskit.circuit.QuantumCircuit.assign_parameters") when assigning a single parameter of a circuit that involves many parameters has been improved.
* Introduced two new classes, [`SingletonInstruction`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonInstruction "qiskit.circuit.singleton.SingletonInstruction") and [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate"), which are subclasses of [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") and [`Gate`](/api/qiskit/0.45/qiskit.circuit.Gate "qiskit.circuit.Gate") respectively, that use a single instance for all objects of that type. The intent behind this class is to minimize the memory and construction overhead of using multiple gates in a circuit with the tradeoff of having global shared state. For this reason this class is only applicable to gates that do not have any unique and/or mutable state stored in an instance. For example, the best example of this is [`XGate`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate") doesn’t contain any state and could leverage [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate") (and does starting in this release), while [`RXGate`](/api/qiskit/0.45/qiskit.circuit.library.RXGate "qiskit.circuit.library.RXGate") stores an angle parameter in an instance and thus can not use [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate") because a single shared global instance can not represent the parameter values.
The other potential issue to be aware of when using singleton classes is that the [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") data model supports some mutable state. Specifically, the [`label`](/api/qiskit/0.45/qiskit.circuit.Instruction#label "qiskit.circuit.Instruction.label"), [`duration`](/api/qiskit/0.45/qiskit.circuit.Instruction#duration "qiskit.circuit.Instruction.duration"), [`unit`](/api/qiskit/0.45/qiskit.circuit.Instruction#unit "qiskit.circuit.Instruction.unit"), and [`condition`](/api/qiskit/0.45/qiskit.circuit.Instruction#condition "qiskit.circuit.Instruction.condition") attributes are all accessible and mutable in the [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") and its direct subclasses. However, this is incompatible with having a shared object via [`SingletonInstruction`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonInstruction "qiskit.circuit.singleton.SingletonInstruction"). For instances of [`SingletonInstruction`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonInstruction "qiskit.circuit.singleton.SingletonInstruction"), setting these attributes directly is not allowed and it will raise an exception. If they are needed for a particular instance, you must ensure you have a mutable instance using [`Instruction.to_mutable()`](/api/qiskit/0.45/qiskit.circuit.Instruction#to_mutable "qiskit.circuit.Instruction.to_mutable") (or use [`Instruction.c_if()`](/api/qiskit/0.45/qiskit.circuit.Instruction#c_if "qiskit.circuit.Instruction.c_if") for [`condition`](/api/qiskit/0.45/qiskit.circuit.Instruction#condition "qiskit.circuit.Instruction.condition")). `label`, `duration` and `unit` can also be given as keyword arguments during class construction.
* The following standard library gates are now instances of [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate"):
> * [`DCXGate`](/api/qiskit/0.45/qiskit.circuit.library.DCXGate "qiskit.circuit.library.DCXGate")
> * [`ECRGate`](/api/qiskit/0.45/qiskit.circuit.library.ECRGate "qiskit.circuit.library.ECRGate")
> * [`HGate`](/api/qiskit/0.45/qiskit.circuit.library.HGate "qiskit.circuit.library.HGate")
> * [`IGate`](/api/qiskit/0.45/qiskit.circuit.library.IGate "qiskit.circuit.library.IGate")
> * [`iSwapGate`](/api/qiskit/0.45/qiskit.circuit.library.iSwapGate "qiskit.circuit.library.iSwapGate")
> * [`SGate`](/api/qiskit/0.45/qiskit.circuit.library.SGate "qiskit.circuit.library.SGate")
> * [`SdgGate`](/api/qiskit/0.45/qiskit.circuit.library.SdgGate "qiskit.circuit.library.SdgGate")
> * [`SwapGate`](/api/qiskit/0.45/qiskit.circuit.library.SwapGate "qiskit.circuit.library.SwapGate")
> * [`SXGate`](/api/qiskit/0.45/qiskit.circuit.library.SXGate "qiskit.circuit.library.SXGate")
> * [`SXdgGate`](/api/qiskit/0.45/qiskit.circuit.library.SXdgGate "qiskit.circuit.library.SXdgGate")
> * [`TGate`](/api/qiskit/0.45/qiskit.circuit.library.TGate "qiskit.circuit.library.TGate")
> * [`TdgGate`](/api/qiskit/0.45/qiskit.circuit.library.TdgGate "qiskit.circuit.library.TdgGate")
> * [`XGate`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate")
> * [`RCCXGate`](/api/qiskit/0.45/qiskit.circuit.library.RCCXGate "qiskit.circuit.library.RCCXGate")
> * [`RC3XGate`](/api/qiskit/0.45/qiskit.circuit.library.RC3XGate "qiskit.circuit.library.RC3XGate")
> * [`YGate`](/api/qiskit/0.45/qiskit.circuit.library.YGate "qiskit.circuit.library.YGate")
> * [`ZGate`](/api/qiskit/0.45/qiskit.circuit.library.ZGate "qiskit.circuit.library.ZGate")
This means that if these classes are instantiated as (e.g.) [`XGate()`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate") using all the constructor defaults, they will all share a single global instance. This results in a large reduction in the memory overhead for > 1 object of these types and significantly faster object construction time.
* Introduced a new class [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate") which is a subclass of [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate") that uses a single instance for all objects of that type. The intent behind this class is to minimize the memory and construction overhead of using multiple gates in a circuit with the tradeoff of having a global shared state. For this reason, this class is only applicable to gates that do not have any unique and/or mutable state stored in an instance. For example, a [`CXGate`](/api/qiskit/0.45/qiskit.circuit.library.CXGate "qiskit.circuit.library.CXGate") doesn’t contain any state and thus can leverage [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate") (and does starting in this release). In contrast, [`CRXGate`](/api/qiskit/0.45/qiskit.circuit.library.CRXGate "qiskit.circuit.library.CRXGate") stores an angle parameter as part of its instance data and thus can not use [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate").
The other potential issue to be aware of when using [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate") is that the original data model of [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate") supports mutation. Specifically, the [`label`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#label "qiskit.circuit.ControlledGate.label"), [`duration`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#duration "qiskit.circuit.ControlledGate.duration"), [`unit`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#unit "qiskit.circuit.ControlledGate.unit"), [`condition`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#condition "qiskit.circuit.ControlledGate.condition"), and [`ctrl_state`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#ctrl_state "qiskit.circuit.ControlledGate.ctrl_state") attributes are all accessible and mutable in the [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate"), but mutation of these attributes on [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate") subclasses is not allowed, and will raise an exception. These attributes can be customized but only at creation time (i.e. via the constructor). In that case, the newly constructed gate will be a separate instance with the custom state instead of the globally shared instance. You can also use the `SingletonControlledGate.to_mutable()` method to get a mutable copy of a gate object and then mutate the attributes like you would on any other [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") object.
* The following standard library gates are now instances of [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate"):
> * [`CHGate`](/api/qiskit/0.45/qiskit.circuit.library.CHGate "qiskit.circuit.library.CHGate")
> * [`CSGate`](/api/qiskit/0.45/qiskit.circuit.library.CSGate "qiskit.circuit.library.CSGate")
> * [`CSdgGate`](/api/qiskit/0.45/qiskit.circuit.library.CSdgGate "qiskit.circuit.library.CSdgGate")
> * [`CSwapGate`](/api/qiskit/0.45/qiskit.circuit.library.CSwapGate "qiskit.circuit.library.CSwapGate")
> * [`CSXGate`](/api/qiskit/0.45/qiskit.circuit.library.CSXGate "qiskit.circuit.library.CSXGate")
> * [`CXGate`](/api/qiskit/0.45/qiskit.circuit.library.CXGate "qiskit.circuit.library.CXGate")
> * [`CCXGate`](/api/qiskit/0.45/qiskit.circuit.library.CCXGate "qiskit.circuit.library.CCXGate")
> * [`C3SXGate`](/api/qiskit/0.45/qiskit.circuit.library.C3SXGate "qiskit.circuit.library.C3SXGate")
> * [`C3XGate`](/api/qiskit/0.45/qiskit.circuit.library.C3XGate "qiskit.circuit.library.C3XGate")
> * [`C4XGate`](/api/qiskit/0.45/qiskit.circuit.library.C4XGate "qiskit.circuit.library.C4XGate")
> * [`CYGate`](/api/qiskit/0.45/qiskit.circuit.library.CYGate "qiskit.circuit.library.CYGate")
> * [`CZGate`](/api/qiskit/0.45/qiskit.circuit.library.CZGate "qiskit.circuit.library.CZGate")
This means that unless a `label`, `condition`, `duration`, `unit`, or `ctrl_state` are set on the instance at creation time they will all share a single global instance whenever a new gate object is created. This results in a large reduction in the memory overhead for > 1 object of these types.
* Added a new method [`Instruction.to_mutable()`](/api/qiskit/0.45/qiskit.circuit.Instruction#to_mutable "qiskit.circuit.Instruction.to_mutable") and attribute [`Instruction.mutable`](/api/qiskit/0.45/qiskit.circuit.Instruction#mutable "qiskit.circuit.Instruction.mutable") which is used to get a mutable copy and check whether an [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") object is mutable. With the introduction of [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate") these methods can be used to have a unified interface to deal with the mutablitiy of instruction objects.
* Added an attribute [`Instruction.base_class`](/api/qiskit/0.45/qiskit.circuit.Instruction#base_class "qiskit.circuit.Instruction.base_class"), which gets the “base” type of an instruction. Many instructions will satisfy `type(obj) == obj.base_class`, however the singleton instances of [`SingletonInstruction`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonInstruction "qiskit.circuit.singleton.SingletonInstruction") and [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate") are subclasses of their base type. You can use the new [`base_class`](/api/qiskit/0.45/qiskit.circuit.Instruction#base_class "qiskit.circuit.Instruction.base_class") attribute to find the base class of these. See the attribute documentation for considerations on when other subclasses may modify their [`base_class`](/api/qiskit/0.45/qiskit.circuit.Instruction#base_class "qiskit.circuit.Instruction.base_class"), and what this means for execution.
* Added the [`UnitaryOverlap`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryOverlap "qiskit.circuit.library.UnitaryOverlap") circuit to the Qiskit circuit library. It can be used to compute the fidelity of states generated by unitaries by looking at the probability of the output distribution in the all-zeros state or, equivalently, by computing the expectation value of the projector onto the all-zeros state. This is useful in applications such as machine learning, and computing excited states in quantum chemistry, to name a few.
<span id="relnotes-0-45-0-stable-0-45-pulse-features" />
### Pulse Features
* Enabled circuit-to-pulse scheduling using [`BackendV2`](/api/qiskit/0.45/qiskit.providers.BackendV2 "qiskit.providers.BackendV2").
```python
# import a fake backend which is a sub-class of BackendV2
from qiskit.providers.fake_provider import FakePerth
from qiskit.compiler.scheduler import schedule
from qiskit.circuit import QuantumCircuit
qc = QuantumCircuit(1, 1)
qc.x(0)
qc.measure(0,0)
sched = schedule(circuits=qc, backend=FakePerth())
```
Since [`BackendV2`](/api/qiskit/0.45/qiskit.providers.BackendV2 "qiskit.providers.BackendV2") was not supported by the [`schedule()`](/api/qiskit/0.45/compiler#qiskit.compiler.schedule "qiskit.compiler.schedule") function, this caused the `schedule()` method to error out when the `backend` argument was supplied with an instance of [`BackendV2`](/api/qiskit/0.45/qiskit.providers.BackendV2 "qiskit.providers.BackendV2"). Refer to [#10837](https://github.com/Qiskit/qiskit/issues/10837) for more information.
<span id="relnotes-0-45-0-stable-0-45-openqasm-features" />
### OpenQASM Features
* The OpenQASM 2 module [`qiskit.qasm2`](/api/qiskit/0.45/qasm2#module-qiskit.qasm2 "qiskit.qasm2") has gained the export functions [`dump()`](/api/qiskit/0.45/qasm2#qiskit.qasm2.dump "qiskit.qasm2.dump") and [`dumps()`](/api/qiskit/0.45/qasm2#qiskit.qasm2.dumps "qiskit.qasm2.dumps"). These are used in a very similar manner to the previous [`QuantumCircuit.qasm()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#qasm "qiskit.circuit.QuantumCircuit.qasm"):
```python
from qiskit import qasm2, QuantumCircuit
qc = QuantumCircuit(2, 2)
qc.h(0)
qc.cx(0, 1)
qc.measure([0, 1], [0, 1])
print(qasm2.dumps(qc))
```
The new functions stem from the same code as [`QuantumCircuit.qasm()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#qasm "qiskit.circuit.QuantumCircuit.qasm"), which will slowly be phased out and replaced with the new paths, to provide a more coherent interface when compared to the OpenQASM 3 ([`qiskit.qasm3`](/api/qiskit/0.45/qasm3#module-qiskit.qasm3 "qiskit.qasm3")) and QPY ([`qiskit.qpy`](/api/qiskit/0.45/qpy#module-qiskit.qpy "qiskit.qpy")) modules. This is particularly important since the method name [`qasm()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#qasm "qiskit.circuit.QuantumCircuit.qasm") gave no indication of the OpenQASM version, and since it was originally added, Qiskit has gained several serialisation modules that could easily become confused.
<span id="relnotes-0-45-0-stable-0-45-qpy-features" />
### QPY Features
* QPY now supports the use of symengine-native serialization and deserialization for objects of type `ParameterExpression` as well as symbolic expressions in Pulse schedule blocks. This is a faster serialization alternative, but not supported in all platforms. Please check that your target platform is supported by the symengine library before setting this option, as it will be **required** by qpy to deserialize the payload.
The feature can be enabled through the `use_symengine` parameter in `qpy.dump()`:
```python
from qiskit.circuit import QuantumCircuit, Parameter
from qiskit import qpy
theta = Parameter("theta")
phi = Parameter("phi")
sum_param = theta + phi
qc = QuantumCircuit(1)
qc.rz(sum_param, 0)
qc.measure_all()
with open('bell.qpy', 'wb') as fd:
qpy.dump(qc, fd, use_symengine=True)
with open('bell.qpy', 'rb') as fd:
new_qc = qpy.load(fd)[0]
```
<span id="relnotes-0-45-0-stable-0-45-quantum-information-features" />
### Quantum Information Features
* Added [`Clifford.from_linear_function()`](/api/qiskit/0.45/qiskit.quantum_info.Clifford#from_linear_function "qiskit.quantum_info.Clifford.from_linear_function") and [`Clifford.from_permutation()`](/api/qiskit/0.45/qiskit.quantum_info.Clifford#from_permutation "qiskit.quantum_info.Clifford.from_permutation") methods that create a [`Clifford`](/api/qiskit/0.45/qiskit.quantum_info.Clifford "qiskit.quantum_info.Clifford") object from [`LinearFunction`](/api/qiskit/0.45/qiskit.circuit.library.LinearFunction "qiskit.circuit.library.LinearFunction") and from [`PermutationGate`](/api/qiskit/0.45/qiskit.circuit.library.PermutationGate "qiskit.circuit.library.PermutationGate") respectively. As a consequence, a [`Clifford`](/api/qiskit/0.45/qiskit.quantum_info.Clifford "qiskit.quantum_info.Clifford") can now be constructed directly from a [`LinearFunction`](/api/qiskit/0.45/qiskit.circuit.library.LinearFunction "qiskit.circuit.library.LinearFunction"), a [`PermutationGate`](/api/qiskit/0.45/qiskit.circuit.library.PermutationGate "qiskit.circuit.library.PermutationGate"), or a quantum circuit containing such gates.
* The [`Operator`](/api/qiskit/0.45/qiskit.quantum_info.Operator "qiskit.quantum_info.Operator") class now has a [`draw()`](/api/qiskit/0.45/qiskit.quantum_info.Operator#draw "qiskit.quantum_info.Operator.draw") method allowing it to be displayed as a text matrix, IPython LaTeX object or LaTeX source. The default draw type still is the ASCII `__repr__` of the operator.
* Added a new method, [`apply_layout()`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp#apply_layout "qiskit.quantum_info.SparsePauliOp.apply_layout"), to the [`SparsePauliOp`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp "qiskit.quantum_info.SparsePauliOp") class. This method is used to apply a [`TranspileLayout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout") layout from the transpiler to a [`SparsePauliOp`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp "qiskit.quantum_info.SparsePauliOp") observable that was built for an input circuit to the transpiler. This enables working with [`BaseEstimator`](/api/qiskit/0.45/qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator") implementations and local transpilation more easily. For example:
```python
from qiskit.circuit.library import RealAmplitudes
from qiskit.quantum_info import SparsePauliOp
from qiskit.primitives import BackendEstimator
from qiskit.compiler import transpile
from qiskit.providers.fake_provider import FakeNairobiV2
psi = RealAmplitudes(num_qubits=2, reps=2)
H1 = SparsePauliOp.from_list([("II", 1), ("IZ", 2), ("XI", 3)])
backend = FakeNairobiV2()
estimator = BackendEstimator(backend=backend, skip_transpilation=True)
thetas = [0, 1, 1, 2, 3, 5]
transpiled_psi = transpile(psi, backend, optimization_level=3)
permuted_op = H1.apply_layout(transpiled_psi.layout)
res = estimator.run(transpiled_psi, permuted_op, thetas)
```
where an input circuit is transpiled locally before it’s passed to `run`. Transpilation expands the original circuit from 2 to 7 qubits (the size of `backend`) and permutes its layout, which is then applied to `H1` using [`apply_layout()`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp#apply_layout "qiskit.quantum_info.SparsePauliOp.apply_layout") to reflect the transformations performed by [`transpile()`](/api/qiskit/0.45/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile").
<span id="relnotes-0-45-0-stable-0-45-transpiler-features" />
### Transpiler Features
* The [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") class is extended to synthesize circuits with objects of type [`AnnotatedOperation`](/api/qiskit/0.45/qiskit.circuit.AnnotatedOperation "qiskit.circuit.AnnotatedOperation").
* A new [`qiskit.passmanager`](/api/qiskit/0.45/passmanager#module-qiskit.passmanager "qiskit.passmanager") module has been added to the Qiskit library. This module implements a generic pass manager and flow controllers, and provides infrastructure to manage execution of pass manager tasks. The module provides base classes for passes ([`GenericPass`](/api/qiskit/0.45/qiskit.passmanager.GenericPass "qiskit.passmanager.GenericPass")) and flow controllers ([`BaseController`](/api/qiskit/0.45/qiskit.passmanager.BaseController "qiskit.passmanager.BaseController")), as well as a new interface class, `passmanager.Task`, to manage the execution of the pass manager (see the `Task.execute()` method). These new classes follow the composite pattern, as flow controllers are collections of passes, and a controller can be recursively nested into the task pipeline. It must also be noted the base classes are not not aware of the input and output object types, and they must be subclassed for a particular program type to optimize. This unified design reduces the complexity of the conventional pass manager, and no longer requires the use of classes such as the `RunningPassManager` to handle the execution logic dispatch and task structure renormalization. The [`qiskit.transpiler`](/api/qiskit/0.45/transpiler#module-qiskit.transpiler "qiskit.transpiler") module has been reorganized to rebuild the existing pass managers based off of the generic pass manager. See upgrade notes for more details.
* Added a new analysis [`SabrePreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabrePreLayout "qiskit.transpiler.passes.SabrePreLayout") pass that creates a starting layout for [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout"), writing the layout into the property set value `sabre_starting_layouts`.
The pass works by augmenting the coupling map with more and more “extra” edges until [`VF2Layout`](/api/qiskit/0.45/qiskit.transpiler.passes.VF2Layout "qiskit.transpiler.passes.VF2Layout") succeeds to find a perfect graph isomorphism. More precisely, the augmented coupling map contains edges between nodes that are within a given distance `d` in the original coupling map, and the value of `d` is increased until an isomorphism is found. The pass also optionally minimizes the number of extra edges involved in the layout until a local minimum is found. This involves removing extra edges and calling [`VF2Layout`](/api/qiskit/0.45/qiskit.transpiler.passes.VF2Layout "qiskit.transpiler.passes.VF2Layout") to check if an isomorphism still exists.
Here is an example of calling the [`SabrePreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabrePreLayout "qiskit.transpiler.passes.SabrePreLayout") before [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout"):
```python
import math
from qiskit.transpiler import CouplingMap, PassManager
from qiskit.circuit.library import EfficientSU2
from qiskit.transpiler.passes import SabrePreLayout, SabreLayout
qc = EfficientSU2(16, entanglement='circular', reps=6, flatten=True)
qc.assign_parameters([math.pi / 2] * len(qc.parameters), inplace=True)
qc.measure_all()
coupling_map = CouplingMap.from_heavy_hex(7)
pm = PassManager(
[
SabrePreLayout(coupling_map=coupling_map),
SabreLayout(coupling_map),
]
)
pm.run(qc)
```
* Added the arguments `coupling_map`, `target` and `use_qubit_indices` to [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") transpiler pass. The argument `target` specifies the target backend, allowing the synthesis plugins called within the pass to access all target-specific information, such as the coupling map and the supported gate set. The argument `coupling_map` only specifies the coupling map, and is only used when `target` is not specified. The argument `use_qubit_indices` indicates whether the high-level-synthesis pass is running before or after the layout is set, that is, whether the qubit indices of higher-level-objects correspond to qubit indices on the target backend.
* Added the arguments `coupling_map`, `target` and `qubits` to [`HighLevelSynthesisPlugin`](/api/qiskit/0.45/qiskit.transpiler.passes.synthesis.plugin.HighLevelSynthesisPlugin "qiskit.transpiler.passes.synthesis.plugin.HighLevelSynthesisPlugin"). The positional argument `target` specifies the target backend, allowing the plugin to access all target-specific information, such as the coupling map, the supported gate set, and so on. The positional argument `coupling_map` only specifies the coupling map, and is only used when `target` is not specified. The positional argument `qubits` specifies the list of qubits over which the higher-level-object is defined, in case the synthesis is done on the physical circuit. The value of `None` indicates that the layout has not yet been chosen.
This enables a cleaner separation of synthesis plugins options into general interface options for plugins (that is, `coupling_map`, `target`, and `qubits`) and into plugin-specific options (a free form configuration dictionary specified via `options`). It is worthwhile to note that this change is backward-compatible, if the options `coupling_map`, etc. are not explicitly added to the plugin’s `run()` method, they will appear as part of `options`.
* The [`DAGCircuit`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit "qiskit.dagcircuit.DAGCircuit") methods [`apply_operation_back()`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit#apply_operation_back "qiskit.dagcircuit.DAGCircuit.apply_operation_back") and [`apply_operation_front()`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit#apply_operation_front "qiskit.dagcircuit.DAGCircuit.apply_operation_front") have gained a `check` keyword argument that can be set `False` to skip validation that the inputs uphold the [`DAGCircuit`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit "qiskit.dagcircuit.DAGCircuit") data-structure invariants. This is useful as a performance optimisation when the DAG is being built from known-good data, such as during transpiler passes.
* The method [`CouplingMap.reduce()`](/api/qiskit/0.45/qiskit.transpiler.CouplingMap#reduce "qiskit.transpiler.CouplingMap.reduce") now accepts an additional argument `check_if_connected`, defaulted to `True`. This corresponds to the previous behavior, checking whether the reduced coupling map remains connected and raising a `CouplingError` if not so. When set to `False`, the check is skipped, allowing disconnected reduced coupling maps.
* The constructor for [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") transpiler pass now accepts additional arguments `equivalence_library`, `basis_gates`, and `min_qubits`. The pass can now unroll custom definitions similarly to [`UnrollCustomDefinitions`](/api/qiskit/0.45/qiskit.transpiler.passes.UnrollCustomDefinitions "qiskit.transpiler.passes.UnrollCustomDefinitions"), and as such completely subsumes the functionality of the latter pass. In particular, [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") is now recursive, fixing an oversight in the initial implementation. Thus, when either `target` or `basis_gates` are specified, [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") recursively synthesizes all high-level objects, annotated operations and custom gates in the circuit, leaving only gates that are supported by the target or belong to the equivalence library. This allows to use [`HighLevelSynthesis`](/api/qiskit/0.45/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis") as a drop-in replacement for [`UnrollCustomDefinitions`](/api/qiskit/0.45/qiskit.transpiler.passes.UnrollCustomDefinitions "qiskit.transpiler.passes.UnrollCustomDefinitions"). On the other hand, when neither `target` nor `basis_gates` are specified, the pass synthesizes only the “top-level” high-level objects and annotated operations, i.e. does not recursively descent into the custom gates `definition` field. This is backward-compatible both with [`UnrollCustomDefinitions`](/api/qiskit/0.45/qiskit.transpiler.passes.UnrollCustomDefinitions "qiskit.transpiler.passes.UnrollCustomDefinitions") (which would not do anything) and with the older behavior of the high level synthesis pass, which allows to use it as an intermediate transform, only synthesizing high-level objects as specified by `HLSConfig`.
* Significantly improved the performance of the [`MergeAdjacentBarriers`](/api/qiskit/0.45/qiskit.transpiler.passes.MergeAdjacentBarriers "qiskit.transpiler.passes.MergeAdjacentBarriers") transpiler pass, which used to rebuild the complete DAG to merge the barriers.
* Added a new keyword argument, `min_qubits`, to the constructor of the [`BasisTranslator`](/api/qiskit/0.45/qiskit.transpiler.passes.BasisTranslator "qiskit.transpiler.passes.BasisTranslator") transpiler pass. When set to a non-zero value this is used to set a minimum number of qubits to filter operations to translate in the circuit. For example, if `min_qubits=3` is set the [`BasisTranslator`](/api/qiskit/0.45/qiskit.transpiler.passes.BasisTranslator "qiskit.transpiler.passes.BasisTranslator") instance will only translate gates in the circuit that operate on 3 or more qubits.
* Added a new keyword argument, `min_qubits`, to the constructor of the [`UnrollCustomDefinitions`](/api/qiskit/0.45/qiskit.transpiler.passes.UnrollCustomDefinitions "qiskit.transpiler.passes.UnrollCustomDefinitions") transpiler pass. When set to a non-zero value this is used to set a minimum number of qubits to filter operations to translate in the circuit. For example, if `min_qubits=3` is set the [`UnrollCustomDefinitions`](/api/qiskit/0.45/qiskit.transpiler.passes.UnrollCustomDefinitions "qiskit.transpiler.passes.UnrollCustomDefinitions") instance will only translate gates in the circuit that operate on 3 or more qubits.
* Added support to the [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") pass to add trials with specified starting layouts. The [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") transpiler pass typically runs multiple layout trials that all start with fully random layouts which then use a routing pass to permute that layout instead of inserting swaps to find a layout which will result in fewer swap gates. This new feature enables running an [`AnalysisPass`](/api/qiskit/0.45/qiskit.transpiler.AnalysisPass "qiskit.transpiler.AnalysisPass") prior to [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") which sets the `"sabre_starting_layout"` field in the property set to provide the [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") with additional starting layouts to use in its internal trials. For example, if you wanted to run [`DenseLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.DenseLayout "qiskit.transpiler.passes.DenseLayout") as the starting point for one trial in [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") you would do something like:
```python
from qiskit.providers.fake_provider import FakeSherbrooke
from qiskit.transpiler import AnalysisPass, PassManager
from qiskit.transpiler.preset_passmanagers import generate_preset_pass_manager
from qiskit.transpiler.passes import DenseLayout
class SabreDenseLayoutTrial(AnalysisPass):
def __init__(self, target):
self.dense_pass = DenseLayout(target=target)
super().__init__()
def run(self, dag):
self.dense_pass.run(dag)
self.property_set["sabre_starting_layouts"] = [self.dense_pass.property_set["layout"]]
backend = FakeSherbrooke()
opt_level_1 = generate_preset_pass_manager(1, backend)
pre_layout = PassManager([SabreDenseLayoutTrial(backend.target)])
opt_level_1.pre_layout = pre_layout
```
Then when the `opt_level_1` [`StagedPassManager`](/api/qiskit/0.45/qiskit.transpiler.StagedPassManager "qiskit.transpiler.StagedPassManager") is run with a circuit the output of the [`DenseLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.DenseLayout "qiskit.transpiler.passes.DenseLayout") pass will be used for one of the [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") trials in addition to the 5 fully random trials that run by default in optimization level 1.
* Two new transpiler passes are added to generate single-pulse RX gate calibrations on the fly. These single-pulse RX calibrations will reduce the gate time in half, as described in P.Gokhale et al, Optimized Quantum Compilation for Near-Term Algorithms with OpenPulse (2020), [arXiv:2004.11205](https://arxiv.org/abs/2004.11205).
To reduce the amount of RX calibration data that needs to be generated, [`NormalizeRXAngle`](/api/qiskit/0.45/qiskit.transpiler.passes.NormalizeRXAngle "qiskit.transpiler.passes.optimization.normalize_rx_angle.NormalizeRXAngle") performs three optimizations: wrapping the [`RXGate`](/api/qiskit/0.45/qiskit.circuit.library.RXGate "qiskit.circuit.library.RXGate") rotation angles to `[0, pi]`, replacing `RX(pi/2)` and `RX(pi)` with [`SXGate`](/api/qiskit/0.45/qiskit.circuit.library.SXGate "qiskit.circuit.library.SXGate") and [`XGate`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate"), and quantizing the rotation angles. This pass is required to be run before [`RXCalibrationBuilder`](/api/qiskit/0.45/qiskit.transpiler.passes.RXCalibrationBuilder "qiskit.transpiler.passes.calibration.rx_builder.RXCalibrationBuilder"), which generates RX calibrations on the fly.
The optimizations performed by [`NormalizeRXAngle`](/api/qiskit/0.45/qiskit.transpiler.passes.NormalizeRXAngle "qiskit.transpiler.passes.NormalizeRXAngle") reduce the amount of calibration data and enable us to take advantage of the more accurate, hardware-calibrated pulses. The calibrations generated by [`RXCalibrationBuilder`](/api/qiskit/0.45/qiskit.transpiler.passes.RXCalibrationBuilder "qiskit.transpiler.passes.RXCalibrationBuilder") are bootstrapped from the [`SXGate`](/api/qiskit/0.45/qiskit.circuit.library.SXGate "qiskit.circuit.library.SXGate") calibration, which should be already present in the target. The amplitude is linearly scaled to achieve the desired arbitrary rotation angle.
Such single-pulse calibrations reduces the [`RXGate`](/api/qiskit/0.45/qiskit.circuit.library.RXGate "qiskit.circuit.library.RXGate") time in half, compared to the conventional sequence that consists of two [`SXGate`](/api/qiskit/0.45/qiskit.circuit.library.SXGate "qiskit.circuit.library.SXGate") pulses. There could be an improvement in fidelity due to this reduction in gate time.
* Added new methods to [`TranspileLayout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout"), [`initial_index_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#initial_index_layout "qiskit.transpiler.TranspileLayout.initial_index_layout") and [`routing_permutation()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#routing_permutation "qiskit.transpiler.TranspileLayout.routing_permutation"), which are used to generate a list view of the [`TranspileLayout.initial_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#initial_layout "qiskit.transpiler.TranspileLayout.initial_layout") and [`TranspileLayout.final_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_layout "qiskit.transpiler.TranspileLayout.final_layout") attributes respectively. For example, if the [`final_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_layout "qiskit.transpiler.TranspileLayout.final_layout") attribute was:
```python
Layout({
qr[0]: 2,
qr[1]: 3,
qr[2]: 0,
qr[3]: 1,
})
```
then [`routing_permutation()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#routing_permutation "qiskit.transpiler.TranspileLayout.routing_permutation") will return:
```python
[2, 3, 0, 1]
```
* Added a new method to [`TranspileLayout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout"), [`initial_virtual_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#initial_virtual_layout "qiskit.transpiler.TranspileLayout.initial_virtual_layout"), which is equivalent to the [`TranspileLayout.initial_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#initial_layout "qiskit.transpiler.TranspileLayout.initial_layout") attribute but gives the option to filter ancilla qubits that were added to the circuit. By default the [`TranspileLayout.initial_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#initial_layout "qiskit.transpiler.TranspileLayout.initial_layout") will typically include any ancillas added by the transpiler.
* Added a new methods, [`final_index_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_index_layout "qiskit.transpiler.TranspileLayout.final_index_layout") and [`final_virtual_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_virtual_layout "qiskit.transpiler.TranspileLayout.final_virtual_layout") to the [`TranspileLayout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout") class. These methods are used to return a final layout (the mapping of input circuit qubits to the final position in the output). This is distinct from the [`final_layout`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_layout "qiskit.transpiler.TranspileLayout.final_layout") attribute which is the permutation caused by routing as a [`Layout`](/api/qiskit/0.45/qiskit.transpiler.Layout "qiskit.transpiler.Layout") object. The [`final_index_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_index_layout "qiskit.transpiler.TranspileLayout.final_index_layout") method returns a list to show the output position for each qubit in the input circuit to the transpiler. For example, with an original circuit:
```python
qc = QuantumCircuit(3)
qc.h(0)
qc.cx(0, 1)
qc.cx(0, 2)
```
and the output from the transpiler was:
```python
tqc = QuantumCircuit(3)
tqc.h(2)
tqc.cx(2, 1)
tqc.swap(0, 1)
tqc.cx(2, 1)
```
then the output from [`final_index_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_index_layout "qiskit.transpiler.TranspileLayout.final_index_layout") would return a list of:
```python
[2, 0, 1]
```
The [`final_virtual_layout()`](/api/qiskit/0.45/qiskit.transpiler.TranspileLayout#final_virtual_layout "qiskit.transpiler.TranspileLayout.final_virtual_layout") returns this as a [`Layout`](/api/qiskit/0.45/qiskit.transpiler.Layout "qiskit.transpiler.Layout") object, so the return from the above example would be:
```python
Layout({
qc.qubits[0]: 2,
qc.qubits[1]: 0,
qc.qubits[2]: 1,
})
```
<span id="relnotes-0-45-0-stable-0-45-visualization-features" />
### Visualization Features
* Added the ability to display conditions as expressions from [`Expr`](/api/qiskit/0.45/circuit_classical#qiskit.circuit.classical.expr.Expr "qiskit.circuit.classical.expr.Expr") in the [`QuantumCircuit.draw()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#draw "qiskit.circuit.QuantumCircuit.draw") method and the [`circuit_drawer()`](/api/qiskit/0.45/qiskit.visualization.circuit_drawer "qiskit.visualization.circuit_drawer") function when visualizing circuits that have [`ControlFlowOp`](/api/qiskit/0.45/qiskit.circuit.ControlFlowOp "qiskit.circuit.ControlFlowOp") instructions.
* Added the `"iqp"` and `"iqp-dark"` color styles for the `matplotlib` circuit drawer, which are based on the IBM Quantum Platform color scheme.
* In `TextDrawer`, operations built from [`ControlFlowOp`](/api/qiskit/0.45/qiskit.circuit.ControlFlowOp "qiskit.circuit.ControlFlowOp"), including `if`, `else`, `while`, `for`, and `switch/case`, whether directly instantiated or built using methods in [`QuantumCircuit`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit"), will now fully display the circuits defined in the ControlFlowOps with brackets to delineate the circuits.
* When defining a custom stylesheet for the pulse timeline drawer [`qiskit.visualization.timeline_drawer()`](/api/qiskit/0.45/qiskit.visualization.timeline_drawer "qiskit.visualization.timeline_drawer"), “generator” functions that have the object attribute `accepts_program` set to `True` will receive an extra keyword argument `program` containing the full scheduled [`QuantumCircuit`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") being drawn.
* The visualizations from the [`plot_gate_map()`](/api/qiskit/0.45/qiskit.visualization.plot_gate_map "qiskit.visualization.plot_gate_map"), [`plot_coupling_map()`](/api/qiskit/0.45/qiskit.visualization.plot_coupling_map "qiskit.visualization.plot_coupling_map"). [`plot_error_map()`](/api/qiskit/0.45/qiskit.visualization.plot_error_map "qiskit.visualization.plot_error_map"), and [`plot_circuit_layout()`](/api/qiskit/0.45/qiskit.visualization.plot_circuit_layout "qiskit.visualization.plot_circuit_layout") functions have been significantly improved for rendering layouts of backends with large numbers of qubits. This was accomplished by leveraging [graphviz](https://graphviz.org/) through rustworkx’s `graphviz_draw()` function to perform a more sophisticated algorithmic graph layout that scales for large numbers of qubits.
![\_images/release\_notes-1.png](/images/api/qiskit/0.45/release_notes-1.avif)
<span id="relnotes-0-45-0-stable-0-45-misc-features" />
### Misc. Features
* Added support for expressing the sign of a [`ParameterExpression`](/api/qiskit/0.45/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression"). Instead of assigning a concrete value and using [`numpy.sign`](https://numpy.org/doc/stable/reference/generated/numpy.sign.html#numpy.sign "(in NumPy v1.26)") or other library functions, the user can use the instance of the [`ParameterExpression`](/api/qiskit/0.45/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression") class to calculate the sign and can work with the sign before the expression is fully assigned.
It can be used as follows:
```python
from qiskit.circuit import Parameter
b = Parameter("phi")
sign_value = b.sign()
print("sign of an unassigned Parameter is: ", sign_value)
print("Sign of a Parameter assigned to -3 is: ", sign_value.assign(b,-3))
```
Refer to [#10360](https://github.com/Qiskit/qiskit/issues/10360) for more details.
* [`Parameter`](/api/qiskit/0.45/qiskit.circuit.Parameter "qiskit.circuit.Parameter") now has an advanced-usage keyword argument `uuid` in its constructor, which can be used to make the [`Parameter`](/api/qiskit/0.45/qiskit.circuit.Parameter "qiskit.circuit.Parameter") compare equal to another of the same name. This should not typically be used by users, and is most useful for custom serialisation and deserialisation.
<span id="relnotes-0-45-0-stable-0-45-circuits-upgrade-notes" />
### Circuits Upgrade Notes
* The [`ControlledGate.definition`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#definition "qiskit.circuit.ControlledGate.definition") of the output from the [`Gate.control()`](/api/qiskit/0.45/qiskit.circuit.Gate#control "qiskit.circuit.Gate.control") method may be different as compared to previous releases. The internal generation of the [`Gate.control()`](/api/qiskit/0.45/qiskit.circuit.Gate#control "qiskit.circuit.Gate.control") method is no longer using the now deprecated [`Unroller`](/api/qiskit/0.45/qiskit.transpiler.passes.Unroller "qiskit.transpiler.passes.Unroller") transpiler pass to generate its definition and this can potentially cause a different definition to be generated. The output [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate") object’s definition will be unitary equivalent to what was generated before. But if you require the exact definition from calling [`Gate.control()`](/api/qiskit/0.45/qiskit.circuit.Gate#control "qiskit.circuit.Gate.control") you can use an earlier release and save the circuit with [`qpy.dump()`](/api/qiskit/0.45/qpy#qiskit.qpy.dump "qiskit.qpy.dump") and then load it with a newer release.
* The property `num_ancilla_qubits` from the class [`PolynomialPauliRotations`](/api/qiskit/0.45/qiskit.circuit.library.PolynomialPauliRotations "qiskit.circuit.library.PolynomialPauliRotations") has been removed, as deprecated in Qiskit 0.23.0. Instead, use the property [`PolynomialPauliRotations.num_ancillas`](/api/qiskit/0.45/qiskit.circuit.library.PolynomialPauliRotations#num_ancillas "qiskit.circuit.library.PolynomialPauliRotations.num_ancillas").
* The following standard library gates:
> * [`DCXGate`](/api/qiskit/0.45/qiskit.circuit.library.DCXGate "qiskit.circuit.library.DCXGate")
> * [`ECRGate`](/api/qiskit/0.45/qiskit.circuit.library.ECRGate "qiskit.circuit.library.ECRGate")
> * [`HGate`](/api/qiskit/0.45/qiskit.circuit.library.HGate "qiskit.circuit.library.HGate")
> * [`IGate`](/api/qiskit/0.45/qiskit.circuit.library.IGate "qiskit.circuit.library.IGate")
> * [`iSwapGate`](/api/qiskit/0.45/qiskit.circuit.library.iSwapGate "qiskit.circuit.library.iSwapGate")
> * [`SGate`](/api/qiskit/0.45/qiskit.circuit.library.SGate "qiskit.circuit.library.SGate")
> * [`SdgGate`](/api/qiskit/0.45/qiskit.circuit.library.SdgGate "qiskit.circuit.library.SdgGate")
> * [`SwapGate`](/api/qiskit/0.45/qiskit.circuit.library.SwapGate "qiskit.circuit.library.SwapGate")
> * [`SXGate`](/api/qiskit/0.45/qiskit.circuit.library.SXGate "qiskit.circuit.library.SXGate")
> * [`SXdgGate`](/api/qiskit/0.45/qiskit.circuit.library.SXdgGate "qiskit.circuit.library.SXdgGate")
> * [`TGate`](/api/qiskit/0.45/qiskit.circuit.library.TGate "qiskit.circuit.library.TGate")
> * [`TdgGate`](/api/qiskit/0.45/qiskit.circuit.library.TdgGate "qiskit.circuit.library.TdgGate")
> * [`XGate`](/api/qiskit/0.45/qiskit.circuit.library.XGate "qiskit.circuit.library.XGate")
> * [`RCCXGate`](/api/qiskit/0.45/qiskit.circuit.library.RCCXGate "qiskit.circuit.library.RCCXGate")
> * [`RC3XGate`](/api/qiskit/0.45/qiskit.circuit.library.RC3XGate "qiskit.circuit.library.RC3XGate")
> * [`YGate`](/api/qiskit/0.45/qiskit.circuit.library.YGate "qiskit.circuit.library.YGate")
> * [`ZGate`](/api/qiskit/0.45/qiskit.circuit.library.ZGate "qiskit.circuit.library.ZGate")
> * [`CHGate`](/api/qiskit/0.45/qiskit.circuit.library.CHGate "qiskit.circuit.library.CHGate")
> * [`CSGate`](/api/qiskit/0.45/qiskit.circuit.library.CSGate "qiskit.circuit.library.CSGate")
> * [`CSdgGate`](/api/qiskit/0.45/qiskit.circuit.library.CSdgGate "qiskit.circuit.library.CSdgGate")
> * [`CSwapGate`](/api/qiskit/0.45/qiskit.circuit.library.CSwapGate "qiskit.circuit.library.CSwapGate")
> * [`CSXGate`](/api/qiskit/0.45/qiskit.circuit.library.CSXGate "qiskit.circuit.library.CSXGate")
> * [`CXGate`](/api/qiskit/0.45/qiskit.circuit.library.CXGate "qiskit.circuit.library.CXGate")
> * [`CCXGate`](/api/qiskit/0.45/qiskit.circuit.library.CCXGate "qiskit.circuit.library.CCXGate")
> * [`C3SXGate`](/api/qiskit/0.45/qiskit.circuit.library.C3SXGate "qiskit.circuit.library.C3SXGate")
> * [`C3XGate`](/api/qiskit/0.45/qiskit.circuit.library.C3XGate "qiskit.circuit.library.C3XGate")
> * [`C4XGate`](/api/qiskit/0.45/qiskit.circuit.library.C4XGate "qiskit.circuit.library.C4XGate")
> * [`CYGate`](/api/qiskit/0.45/qiskit.circuit.library.CYGate "qiskit.circuit.library.CYGate")
> * [`CZGate`](/api/qiskit/0.45/qiskit.circuit.library.CZGate "qiskit.circuit.library.CZGate")
are no longer able to set [`label`](/api/qiskit/0.45/qiskit.circuit.Gate#label "qiskit.circuit.Gate.label"), [`condition`](/api/qiskit/0.45/qiskit.circuit.Gate#condition "qiskit.circuit.Gate.condition"), [`duration`](/api/qiskit/0.45/qiskit.circuit.Gate#duration "qiskit.circuit.Gate.duration"), or [`unit`](/api/qiskit/0.45/qiskit.circuit.Gate#unit "qiskit.circuit.Gate.unit") (and [`ctrl_state`](/api/qiskit/0.45/qiskit.circuit.ControlledGate#ctrl_state "qiskit.circuit.ControlledGate.ctrl_state") for [`ControlledGate`](/api/qiskit/0.45/qiskit.circuit.ControlledGate "qiskit.circuit.ControlledGate") subclasses) after instantiating an object anymore. You can still set [`condition`](/api/qiskit/0.45/qiskit.circuit.Gate#condition "qiskit.circuit.Gate.condition") through the use [`c_if()`](/api/qiskit/0.45/qiskit.circuit.Gate#c_if "qiskit.circuit.Gate.c_if"). You can use [`to_mutable()`](/api/qiskit/0.45/qiskit.circuit.Gate#to_mutable "qiskit.circuit.Gate.to_mutable") to get a mutable copy of the instruction and then use the setter on that copy instead of the original object. `label`, `duration` and `unit` can be given as keyword arguments to these gates at construction time, and a mutable instance will be returned automatically. This change was necessary as part of converting these classes to be [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate") and [`SingletonControlledGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonControlledGate "qiskit.circuit.singleton.SingletonControlledGate") types which greatly reduces the memory footprint of repeated instances of these gates.
* For anything that interacts with [`Gate`](/api/qiskit/0.45/qiskit.circuit.Gate "qiskit.circuit.Gate"), [`Operation`](/api/qiskit/0.45/qiskit.circuit.Operation "qiskit.circuit.Operation"), or [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") objects or works with these as part of a [`QuantumCircuit`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") or [`DAGCircuit`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit "qiskit.dagcircuit.DAGCircuit") classes, it is important to note that the use of shared references for instances is much more common now. Previously, it was possible to reuse and share an instance of a circuit operation, but it wasn’t very commonly used and a copy would generate a unique instance. This has changed starting in this release because of [`SingletonInstruction`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonInstruction "qiskit.circuit.singleton.SingletonInstruction") and [`SingletonGate`](/api/qiskit/0.45/circuit_singleton#qiskit.circuit.singleton.SingletonGate "qiskit.circuit.singleton.SingletonGate") being made available (and a large number of standard library gates now built off of them). If your usage of these objects is assuming unique instances for every circuit operation, this becomes a potential issue, as now a shared state will be reused between operations of the same type (that will persist through copy and deep copies). You can rely on the [`Instruction.mutable`](/api/qiskit/0.45/qiskit.circuit.Instruction#mutable "qiskit.circuit.Instruction.mutable") attribute to check the mutability of an object or use [`Instruction.to_mutable()`](/api/qiskit/0.45/qiskit.circuit.Instruction#to_mutable "qiskit.circuit.Instruction.to_mutable") to get a mutable copy of any instruction.
* More [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") instances (those that return singletons) no longer strictly satisfy (for example):
```python
type(XGate()) is XGate
```
The returned object will, however, still be a standard subclass so [`isinstance()`](https://docs.python.org/3/library/functions.html#isinstance "(in Python v3.12)") (the correct way to do type checking) will continue to work correctly. Several instructions already had this property (e.g. [`MCXGate`](/api/qiskit/0.45/qiskit.circuit.library.MCXGate "qiskit.circuit.library.MCXGate")), but it is now more common as many more standard gates will do this.
If you require the “base” type of a gate for some reason, omitting the synthetic singleton subclasses, which cannot be instantiated, see [`Instruction.base_class`](/api/qiskit/0.45/qiskit.circuit.Instruction#base_class "qiskit.circuit.Instruction.base_class").
* The definition of [`UnitaryGate`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryGate "qiskit.circuit.library.UnitaryGate") for single qubit unitaries is now in terms of [`UGate`](/api/qiskit/0.45/qiskit.circuit.library.UGate "qiskit.circuit.library.UGate") instead of the legacy [`U3Gate`](/api/qiskit/0.45/qiskit.circuit.library.U3Gate "qiskit.circuit.library.U3Gate") class.
<span id="relnotes-0-45-0-stable-0-45-providers-upgrade-notes" />
### Providers Upgrade Notes
* The [`QasmSimulatorPy`](/api/qiskit/0.45/qiskit.providers.basicaer.QasmSimulatorPy "qiskit.providers.basicaer.QasmSimulatorPy") python-based simulator included in [`qiskit.providers.basicaer`](/api/qiskit/0.45/providers_basicaer#module-qiskit.providers.basicaer "qiskit.providers.basicaer") now includes `'h'` ([`HGate`](/api/qiskit/0.45/qiskit.circuit.library.HGate "qiskit.circuit.library.HGate")), `'p'` ([`PhaseGate`](/api/qiskit/0.45/qiskit.circuit.library.PhaseGate "qiskit.circuit.library.PhaseGate")), and `'u'` ([`UGate`](/api/qiskit/0.45/qiskit.circuit.library.UGate "qiskit.circuit.library.UGate")) in its basis gate set.
* The argument `channel` in the method [`PulseBackendConfiguration.control()`](/api/qiskit/0.45/qiskit.providers.models.PulseBackendConfiguration#control "qiskit.providers.models.PulseBackendConfiguration.control") is removed. It was deprecated in Qiskit 0.33 (with Terra 0.19), released on Dec 2021. Instead use the `qubits` argument.
* Replaced the argument `qobj[Qobj]` in [`QasmSimulatorPy.run()`](/api/qiskit/0.45/qiskit.providers.basicaer.QasmSimulatorPy#run "qiskit.providers.basicaer.QasmSimulatorPy.run") with `run_input[QuantumCircuit or list]`
Here is an example to migrate your code:
```python
# Importing necessary Qiskit libraries
from qiskit import transpile, QuantumCircuit
from qiskit.aer import QasmSimulator
# Defining the Quantum Circuit
qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()
# Transpile the circuit to optimize for the target simulator
simulator = QasmSimulator()
transpiled_circuit = transpile(qc, simulator)
# Run the simulation
job = simulator.run(transpiled_circuit, shots=1024)
# Get the simulation result
result = job.result()
```
All these were deprecated since 0.22 (released on October 13, 2022) and now they are removed.
<span id="relnotes-0-45-0-stable-0-45-pulse-upgrade-notes" />
### Pulse Upgrade Notes
* The functions `qiskit.scheduler.utils.format_meas_map()`, `qiskit.scheduler.utils.measure()`, and `qiskit.scheduler.utils.measure_all()` had been moved to `qiskit.pulse.utils.format_meas_map()`, `qiskit.pulse.macros.measure()`, and `qiskit.pulse.macros.measure_all()` respectively. The previous location was deprecated in Qiskit 0.20.0 (Terra 0.15.0, released on 2020-08-10) and it is no longer supported.
* The methods `to_dict` in the classes [`pulse.transforms.AlignmentKind`](/api/qiskit/0.45/pulse#qiskit.pulse.transforms.AlignmentKind "qiskit.pulse.transforms.AlignmentKind"), [`pulse.transforms.AlignEquispaced`](/api/qiskit/0.45/qiskit.pulse.transforms.AlignEquispaced "qiskit.pulse.transforms.AlignEquispaced"), and [`pulse.transforms.AlignFunc`](/api/qiskit/0.45/qiskit.pulse.transforms.AlignFunc "qiskit.pulse.transforms.AlignFunc") are removed. They were deprecatedin Qiskit 0.37 (with Terra 0.21), released on June 2022.
<span id="relnotes-0-45-0-stable-0-45-qpy-upgrade-notes" />
### QPY Upgrade Notes
* The use of the keyword `circuits` for the first positional argument in the function [`qiskit.qpy.dump()`](/api/qiskit/0.45/qpy#qiskit.qpy.dump "qiskit.qpy.dump") is removed as its usage was deprecated in Qiskit 0.37 (with Terra 0.21), released on June 2022. Instead, use the keyword `programs` can be used instead (or just pass the argument in positionally), which behaves identically.
<span id="relnotes-0-45-0-stable-0-45-quantum-information-upgrade-notes" />
### Quantum Information Upgrade Notes
* The method [`qiskit.quantum_info.pauli_basis()`](/api/qiskit/0.45/qiskit.quantum_info.pauli_basis "qiskit.quantum_info.pauli_basis") does not accept the `pauli_list` argument any more. It was deprecated in Qiskit 0.39 (with Terra 0.22), released on Oct 2022.
* The function `random_stabilizer_table` in the `qiskit.quantum_info.random` module is removed. It was deprecated in Qiskit 0.39 (with Terra 0.22), released on Oct 2022. Instead, use `qiskit.quantum_info.random.random_pauli_list()`.
* The classes `qiskit.quantum_info.PauliTable` and `qiskit.quantum_info.StabilizerTable` are removed. The function `random_pauli_table()` is also removed. They were deprecated in Qiskit 0.43 (with Terra 0.24), released in May 2023. Instead, you should use [`PauliList`](/api/qiskit/0.45/qiskit.quantum_info.PauliList "qiskit.quantum_info.PauliList") and [`random_pauli_list()`](/api/qiskit/0.45/quantum_info#qiskit.quantum_info.random_pauli_list "qiskit.quantum_info.random_pauli_list").
* The arguments `z` and `x` to the initializer of to [`Pauli`](/api/qiskit/0.45/qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli") were removed, as deprecated in Qiskit Terra 0.17 (released on April, 2021). A pair of `x` and `z` should be passed positionally as a single tuple instead (`Pauli((z, x))`).
* The argument `label` to the initializer of [`Pauli`](/api/qiskit/0.45/qiskit.quantum_info.Pauli "qiskit.quantum_info.Pauli") was removed, as deprecated in Qiskit Terra 0.17 (released on April, 2021). Pass the label positionally instead, such as `Pauli("XYZ")`.
* Importing from `qiskit.quantum_info.operators.pauli` is not allowed anymore, as it was deprecated in Qiskit Terra 0.21 (released on June, 2022). Import directly from `qiskit.quantum_info` instead.
<span id="relnotes-0-45-0-stable-0-45-synthesis-upgrade-notes" />
### Synthesis Upgrade Notes
* The parameter `order` in [`synthesis.SuzukiTrotter`](/api/qiskit/0.45/qiskit.synthesis.SuzukiTrotter "qiskit.synthesis.SuzukiTrotter") constructor raises an exception instead of deprecation warning when set in an odd number. Suzuki product formulae are symmetric and therefore only defined for even orders.
<span id="relnotes-0-45-0-stable-0-45-transpiler-upgrade-notes" />
### Transpiler Upgrade Notes
* As a consequence of the pass manager refactoring efforts, existing flow controllers: [`FlowControllerLinear`](/api/qiskit/0.45/qiskit.passmanager.FlowControllerLinear "qiskit.passmanager.FlowControllerLinear"), [`ConditionalController`](/api/qiskit/0.45/qiskit.passmanager.ConditionalController "qiskit.passmanager.ConditionalController"), and [`DoWhileController`](/api/qiskit/0.45/qiskit.passmanager.DoWhileController "qiskit.passmanager.DoWhileController") are now subclasses of the [`BaseController`](/api/qiskit/0.45/qiskit.passmanager.BaseController "qiskit.passmanager.BaseController"). Note that these controllers have dropped the implementation of the [`__iter__()`](https://docs.python.org/3/reference/datamodel.html#object.__iter__ "(in Python v3.12)") method. They are now only iterable in the context of a flow-controller execution, which threads the compilation state through after each inner task is executed.
* The functionalitly of the `RunningPassManager` class has been superseded by the new pass manager framework ([`BasePassManager`](/api/qiskit/0.45/qiskit.passmanager.BasePassManager "qiskit.passmanager.BasePassManager") and [`BaseController`](/api/qiskit/0.45/qiskit.passmanager.BaseController "qiskit.passmanager.BaseController")). The running pass manager is now a stateless flow controller (essentially, an alias of [`FlowControllerLinear`](/api/qiskit/0.45/qiskit.passmanager.FlowControllerLinear "qiskit.passmanager.FlowControllerLinear")), as the pass manager is responsible for the construction of task pipeline, while the controller is responsible for the execution of associated tasks. Subclassing the `RunningPassManager` is no longer recommended, and this class will be completely replaced with the flow controller in future releases.
* A new class, [`WorkflowStatus`](/api/qiskit/0.45/qiskit.passmanager.WorkflowStatus "qiskit.passmanager.WorkflowStatus"), has been introduced to track the status of the pass manager workflow. This portable object is created when the pass manager is run, and handed over to the underlying tasks. Such status was previously managed by the `RunningPassManager` with instance variables.
* The transpiler-specific [`transpiler.PassManager`](/api/qiskit/0.45/qiskit.transpiler.PassManager "qiskit.transpiler.PassManager") (used in [`transpile()`](/api/qiskit/0.45/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile")) is now a subclass of [`passmanager.BasePassManager`](/api/qiskit/0.45/qiskit.passmanager.BasePassManager "qiskit.passmanager.BasePassManager"). However, this class hierarchy change doesn’t introduce any breaking change to the public-facing API.
* Exceptions raised during pass-manager execution now inherit from the newly introduced [`PassManagerError`](/api/qiskit/0.45/passmanager#qiskit.passmanager.PassManagerError "qiskit.passmanager.PassManagerError"). A generic failure of the pass-manager machinery will raise [`PassManagerError`](/api/qiskit/0.45/passmanager#qiskit.passmanager.PassManagerError "qiskit.passmanager.PassManagerError") for general pass managers, but the transpiler-specific `transpile.PassManager` will currently wrap this in its specific [`TranspilerError`](/api/qiskit/0.45/transpiler#qiskit.transpiler.TranspilerError "qiskit.transpiler.TranspilerError") for backwards compatibility. This wrapping will be removed in the future.
* The use of `FencedObject` in the pass manager framework has been removed. This wrapper class cannot protect mutable object attributes from modification, and this should not be an issue for properly implemented code. Analysis passes should not modify an input IR, controllers should not update the property set, and so forth. It’s the pass manager developer’s responsibility to ensure that the pass is not modifying object attributes,
* The plugin name `default` is reserved for the [plugin stages](/api/qiskit/0.45/transpiler_plugins#stage-table) `init`, `layout`, `optimization`, and `scheduling`. These stages previously did not reserve this plugin name, but the `default` name is now used to represent Qiskit’s built-in default method for these stages. If you were using these names for plugins on these stages these will conflict with Qiskit’s usage and you should rename your plugin.
* Disabled the use of the [`RemoveResetInZeroState`](/api/qiskit/0.45/qiskit.transpiler.passes.RemoveResetInZeroState "qiskit.transpiler.passes.RemoveResetInZeroState") class in the preset passmanagers. Previously, when [`transpile()`](/api/qiskit/0.45/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") or [`generate_preset_pass_manager()`](/api/qiskit/0.45/transpiler_preset#qiskit.transpiler.preset_passmanagers.generate_preset_pass_manager "qiskit.transpiler.preset_passmanagers.generate_preset_pass_manager") was run with `optimization_level` at level 1, 2, or 3, it would run [`RemoveResetInZeroState`](/api/qiskit/0.45/qiskit.transpiler.passes.RemoveResetInZeroState "qiskit.transpiler.passes.RemoveResetInZeroState"). However, this pass prohibited the notion of arbitrary initial states unless explicitly set to zeros with resets. If you need to run the pass as part of your compilation pipeline, you can run something like:
```python
pm = generate_preset_pass_manager(1, backend)
pm.init.append(RemoveResetInZeroState())
pm.run(circuit)
```
to retain this functionality for your circuit compilation.
* The deprecated transpiler routing pass, `BIPMapping` has been removed. It was marked as deprecated in the Qiskit 0.43.0 release. It has been replaced by an external plugin package: `qiskit-bip-mapper`. Details for this new package can be found at the package’s github repository:
> [https://github.com/qiskit-community/qiskit-bip-mapper](https://github.com/qiskit-community/qiskit-bip-mapper)
The pass was made into a separate plugin package for two reasons: first, the dependency on CPLEX makes it harder to use, and secondly, the plugin package integrates more cleanly with [`transpile()`](/api/qiskit/0.45/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile"). The optional extra `bip-mapper` to install `cplex` and `docplex` to support this pass has been removed as nothing in Qiskit optionally requires it anymore.
* The argument `qubits` in the method [`InstructionDurations.get()`](/api/qiskit/0.45/qiskit.transpiler.InstructionDurations#get "qiskit.transpiler.InstructionDurations.get"), does not accept [`Qubit`](/api/qiskit/0.45/qiskit.circuit.Qubit "qiskit.circuit.Qubit") (or a list of them) any more. This functionality was deprecated in Qiskit 0.33 (with Terra 0.19), released on Dec 2021. Instead, use an integer for the qubit indices.
* Removed the argument `qubit_channel_mapping` in [`RZXCalibrationBuilder`](/api/qiskit/0.45/qiskit.transpiler.passes.RZXCalibrationBuilder "qiskit.transpiler.passes.RZXCalibrationBuilder"), which was deprecated in Qiskit 0.39 (released on Oct 2022, with qiskit-terra 0.22)
* In [`transpiler.CouplingMap`](/api/qiskit/0.45/qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap") method `subgraph` is removed as deprecated in 0.20. `reduce()` can be used in place of method `subgraph`.
<span id="relnotes-0-45-0-stable-0-45-visualization-upgrade-notes" />
### Visualization Upgrade Notes
* Removed support for using the keyword `rho` for the first positional argument in [`plot_state_hinton()`](/api/qiskit/0.45/qiskit.visualization.plot_state_hinton "qiskit.visualization.plot_state_hinton"), [`plot_bloch_multivector()`](/api/qiskit/0.45/qiskit.visualization.plot_bloch_multivector "qiskit.visualization.plot_bloch_multivector"), [`plot_state_city()`](/api/qiskit/0.45/qiskit.visualization.plot_state_city "qiskit.visualization.plot_state_city"), [`plot_state_paulivec()`](/api/qiskit/0.45/qiskit.visualization.plot_state_paulivec "qiskit.visualization.plot_state_paulivec"), and [`plot_state_qsphere()`](/api/qiskit/0.45/qiskit.visualization.plot_state_qsphere "qiskit.visualization.plot_state_qsphere"). The use of `rho` has been replaced by `state`, which can be used instead. Removed `qiskit.scheduler.utils` as all contained functions were moved to `qiskit.pulse.macros` and `qiskit.pulse.utils`. All these were deprecated since 0.15 (released on August 06, 2020) and now they are removed.
* The class constructor arguments `qregs`, `cregs`, `layout` and `global_phase` for `visualization.QCircuitImage` are removed, as they were deprecated in 0.20.
* The visualization functions: [`plot_gate_map()`](/api/qiskit/0.45/qiskit.visualization.plot_gate_map "qiskit.visualization.plot_gate_map"), [`plot_coupling_map()`](/api/qiskit/0.45/qiskit.visualization.plot_coupling_map "qiskit.visualization.plot_coupling_map"). [`plot_error_map()`](/api/qiskit/0.45/qiskit.visualization.plot_error_map "qiskit.visualization.plot_error_map"), and [`plot_circuit_layout()`](/api/qiskit/0.45/qiskit.visualization.plot_circuit_layout "qiskit.visualization.plot_circuit_layout") now depend on [graphviz](https://graphviz.org/) being installed to function. This change was necessary to enable visualizing backends with larger numbers of qubits. This additional external requirement is in addition to the existing optional dependencies these functions previously required. You find details on how to install graphviz here: [https://graphviz.org/download/](https://graphviz.org/download/)
<span id="relnotes-0-45-0-stable-0-45-misc-upgrade-notes" />
### Misc. Upgrade Notes
* The [`QuasiDistribution`](/api/qiskit/0.45/qiskit.result.QuasiDistribution "qiskit.result.QuasiDistribution") values might include floating-point errors. `QuasiDistribution.__repr__` rounds using `numpy.round()` and the parameter `ndigits` can be manipulated with the class attribute `__ndigits__`. The default is `15`.
* The class `qiskit.qobj.Qobj` is removed. It was deprecated in Qiskit 0.33 (with Terra 0.19), released on Dec 2021. Instead, use [`qiskit.qobj.QasmQobj`](/api/qiskit/0.45/qiskit.qobj.QasmQobj "qiskit.qobj.QasmQobj") or [`qiskit.qobj.PulseQobj`](/api/qiskit/0.45/qiskit.qobj.PulseQobj "qiskit.qobj.PulseQobj").
* The decorator `qiskit.utils.deprecation.deprecate_function()` has been deprecated since Qiskit 0.39.0 (released on October 2022, with qiskit-terra 0.22.0) and now is been removed. Use [`qiskit.utils.deprecate_func()`](/api/qiskit/0.45/utils#qiskit.utils.deprecate_func "qiskit.utils.deprecate_func") instead.
* The function [`execute()`](/api/qiskit/0.45/execute#qiskit.execute_function.execute "qiskit.execute_function.execute") does not accept the arguments `qobj_id` and `qobj_header` any more. Their use was deprecated in Qiskit 0.37 (with Terra 0.21), released on June 2022.
* The transpilation pass `qiskit.transpiler.passes.CXDirection` is removed. Its use was deprecated in Qiskit 0.37 (with Terra 0.21), released on June 2022. Instead, use the more generic [`GateDirection`](/api/qiskit/0.45/qiskit.transpiler.passes.GateDirection "qiskit.transpiler.passes.GateDirection") pass.
* The transpilation pass `qiskit.transpiler.passes.CheckCXDirection` is removed. Its use was deprecated in Qiskit 0.37 (with Terra 0.21), released on June 2022. Instead, use the more generic [`CheckGateDirection`](/api/qiskit/0.45/qiskit.transpiler.passes.CheckGateDirection "qiskit.transpiler.passes.CheckGateDirection") pass.
* Building Qiskit from source now requires a Rust compiler compatible with language version 1.64. This has been increased from the previous minimum supported Rust version of 1.61 for building earlier versions of Qiskit.
<span id="relnotes-0-45-0-stable-0-45-algorithms-deprecations" />
### Algorithms Deprecations
* The algorithm utils in `qiskit.utils.validation` and `qiskit.utils.algorithm_globals` are now deprecated and will be removed in no less than 3 months from the release date. These utils were introduced with the `qiskit.algorithms` module to support legacy and primitive-based algorithm workflows. Now that `qiskit.algorithms` is deprecated and the primitive-based algorithms codebase has been migrated to a standalone [library](https://github.com/qiskit-community/qiskit-algorithms), these utils are no longer used in the context of Qiskit. If your application allows it, we recommend that you migrate your code to use [qiskit\_algorithms](https://github.com/qiskit-community/qiskit-algorithms), where you will be able to import the relevant utilities in `algorithm_globals` and `validation` from `qiskit_algorithms.utils`. Please note that legacy functionality has not been migrated to the new package.
<span id="relnotes-0-45-0-stable-0-45-circuits-deprecations" />
### Circuits Deprecations
* Passing `None` as the `qargs` or `cargs` arguments to [`DAGCircuit.apply_operation_back()`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit#apply_operation_back "qiskit.dagcircuit.DAGCircuit.apply_operation_back") or [`apply_operation_front()`](/api/qiskit/0.45/qiskit.dagcircuit.DAGCircuit#apply_operation_front "qiskit.dagcircuit.DAGCircuit.apply_operation_front") is deprecated and will be removed in Qiskit 1.0. This has been explicitly against the typing documentation for some time, but silently accepted by Qiskit. Instead, simply pass `()` rather than `None`.
* The method [`QuantumCircuit.bind_parameters()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#bind_parameters "qiskit.circuit.QuantumCircuit.bind_parameters") is now deprecated and will be removed from the codebase in no less than 3 months from the release date. Its functionality overlapped highly with [`QuantumCircuit.assign_parameters()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#assign_parameters "qiskit.circuit.QuantumCircuit.assign_parameters"), and can be totally replaced by it. Please use [`QuantumCircuit.assign_parameters()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#assign_parameters "qiskit.circuit.QuantumCircuit.assign_parameters") instead.
* Deprecate duplicate gate methods on [`QuantumCircuit`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit"). The rule applied is that the method names reflect that gate names, e.g. the [`CXGate`](/api/qiskit/0.45/qiskit.circuit.library.CXGate "qiskit.circuit.library.CXGate") is added via [`QuantumCircuit.cx()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#cx "qiskit.circuit.QuantumCircuit.cx") and not [`QuantumCircuit.cnot()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#cnot "qiskit.circuit.QuantumCircuit.cnot"). The deprecations are:
* [`QuantumCircuit.cnot()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#cnot "qiskit.circuit.QuantumCircuit.cnot") in favor of [`QuantumCircuit.cx()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#cx "qiskit.circuit.QuantumCircuit.cx")
* [`QuantumCircuit.toffoli()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#toffoli "qiskit.circuit.QuantumCircuit.toffoli") in favor of [`QuantumCircuit.ccx()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#ccx "qiskit.circuit.QuantumCircuit.ccx")
* [`QuantumCircuit.fredkin()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#fredkin "qiskit.circuit.QuantumCircuit.fredkin") in favor of [`QuantumCircuit.cswap()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#cswap "qiskit.circuit.QuantumCircuit.cswap")
* [`QuantumCircuit.mct()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#mct "qiskit.circuit.QuantumCircuit.mct") in favor of [`QuantumCircuit.mcx()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#mcx "qiskit.circuit.QuantumCircuit.mcx")
* [`QuantumCircuit.i()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#i "qiskit.circuit.QuantumCircuit.i") in favor of [`QuantumCircuit.id()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#id "qiskit.circuit.QuantumCircuit.id")
Note that [`QuantumCircuit.i()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#i "qiskit.circuit.QuantumCircuit.i") is the only exception to the rule above, but since [`QuantumCircuit.id()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#id "qiskit.circuit.QuantumCircuit.id") more intuively represents the identity and is used more, we chose it over its counterpart.
* To streamline the structure of Qiskit’s gates and operations, the [`qiskit.extensions`](/api/qiskit/0.45/extensions#module-qiskit.extensions "qiskit.extensions") module is pending deprecation and will be deprecated in a future release. The following objects have been moved to [`qiskit.circuit.library`](/api/qiskit/0.45/circuit_library#module-qiskit.circuit.library "qiskit.circuit.library")
* [`DiagonalGate`](/api/qiskit/0.45/qiskit.circuit.library.DiagonalGate "qiskit.circuit.library.DiagonalGate"),
* [`HamiltonianGate`](/api/qiskit/0.45/qiskit.circuit.library.HamiltonianGate "qiskit.circuit.library.HamiltonianGate"),
* [`Initialize`](/api/qiskit/0.45/qiskit.circuit.library.Initialize "qiskit.circuit.library.Initialize"),
* [`Isometry`](/api/qiskit/0.45/qiskit.circuit.library.Isometry "qiskit.circuit.library.Isometry"),
* `MCGupDiag`,
* [`UCGate`](/api/qiskit/0.45/qiskit.circuit.library.UCGate "qiskit.circuit.library.UCGate"),
* [`UCPauliRotGate`](/api/qiskit/0.45/qiskit.circuit.library.UCPauliRotGate "qiskit.circuit.library.UCPauliRotGate"),
* [`UCRXGate`](/api/qiskit/0.45/qiskit.circuit.library.UCRXGate "qiskit.circuit.library.UCRXGate"),
* [`UCRYGate`](/api/qiskit/0.45/qiskit.circuit.library.UCRYGate "qiskit.circuit.library.UCRYGate"),
* [`UCRZGate`](/api/qiskit/0.45/qiskit.circuit.library.UCRZGate "qiskit.circuit.library.UCRZGate"),
* [`UnitaryGate`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryGate "qiskit.circuit.library.UnitaryGate").
These instructions have already been deprecated in this release,
* [`SingleQubitUnitary`](/api/qiskit/0.45/qiskit.extensions.SingleQubitUnitary "qiskit.extensions.SingleQubitUnitary"), instead use [`library.UnitaryGate`](/api/qiskit/0.45/qiskit.circuit.library.UnitaryGate "qiskit.circuit.library.UnitaryGate"),
* [`Snapshot`](/api/qiskit/0.45/qiskit.extensions.Snapshot "qiskit.extensions.Snapshot"), which has been superseded by Qiskit Aer’s save instructions,
along with their circuit methods
* [`QuantumCircuit.snapshot()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#snapshot "qiskit.circuit.QuantumCircuit.snapshot"),
* [`QuantumCircuit.squ()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#squ "qiskit.circuit.QuantumCircuit.squ").
In addition, the following circuit methods are pending deprecation
* [`QuantumCircuit.diagonal()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#diagonal "qiskit.circuit.QuantumCircuit.diagonal"),
* [`QuantumCircuit.hamiltonian()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#hamiltonian "qiskit.circuit.QuantumCircuit.hamiltonian"),
* [`QuantumCircuit.isometry()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#isometry "qiskit.circuit.QuantumCircuit.isometry") and [`QuantumCircuit.iso()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#iso "qiskit.circuit.QuantumCircuit.iso"),
* [`QuantumCircuit.uc()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#uc "qiskit.circuit.QuantumCircuit.uc"),
* [`QuantumCircuit.ucrx()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#ucrx "qiskit.circuit.QuantumCircuit.ucrx"),
* [`QuantumCircuit.ucry()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#ucry "qiskit.circuit.QuantumCircuit.ucry"),
* [`QuantumCircuit.ucrz()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#ucrz "qiskit.circuit.QuantumCircuit.ucrz").
Since the entire module is pending deprecation, so is [`ExtensionError`](/api/qiskit/0.45/extensions#qiskit.extensions.ExtensionError "qiskit.extensions.ExtensionError").
* The little-used [`QuantumCircuit`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") class data attributes [`header`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#header "qiskit.circuit.QuantumCircuit.header") and [`extension_lib`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#extension_lib "qiskit.circuit.QuantumCircuit.extension_lib") are deprecated and scheduled for removal. These respectively held strings of the OpenQASM 2.0 version header statement and `qelib1.inc` include statement. No alternative will be provided; these were mostly intended as internal details.
<span id="relnotes-0-45-0-stable-0-45-transpiler-deprecations" />
### Transpiler Deprecations
* The flow controller factory method [`FlowController.controller_factory()`](/api/qiskit/0.45/qiskit.passmanager.FlowController#controller_factory "qiskit.passmanager.FlowController.controller_factory") is deprecated along with [`FlowController.add_flow_controller()`](/api/qiskit/0.45/qiskit.passmanager.FlowController#add_flow_controller "qiskit.passmanager.FlowController.add_flow_controller") and [`FlowController.remove_flow_controller()`](/api/qiskit/0.45/qiskit.passmanager.FlowController#remove_flow_controller "qiskit.passmanager.FlowController.remove_flow_controller"). In the future, task construction with keyword arguments in the [`BasePassManager.append()`](/api/qiskit/0.45/qiskit.passmanager.BasePassManager#append "qiskit.passmanager.BasePassManager.append") method will also be deprecated. Controllers must be explicitly instantiated and appended to the pass manager. For example, the previously used conventional syntax
```python
pm.append([task1, task2], condition=lambda x: x["value1"] > 10)
```
must be replaced with
```python
controller = ConditionalController([task1, task2], condition=lambda x: x["value1"] > 10)
pm.append(controller)
```
The latter allows more precise control on the order of controllers especially when multiple keyword arguments are specified together, and allows for the construction of general flow controllers that may have more than one pipeline or do not take a single simple conditional function in their constructors.
* The [`FlowControllerLinear.append()`](/api/qiskit/0.45/qiskit.passmanager.FlowControllerLinear#append "qiskit.passmanager.FlowControllerLinear.append"), [`DoWhileController.append()`](/api/qiskit/0.45/qiskit.passmanager.DoWhileController#append "qiskit.passmanager.DoWhileController.append"), and [`ConditionalController.append()`](/api/qiskit/0.45/qiskit.passmanager.ConditionalController#append "qiskit.passmanager.ConditionalController.append") methods are all deprecated immediately. The construction of the pass manager task pipeline is now the role of [`BasePassManager`](/api/qiskit/0.45/qiskit.passmanager.BasePassManager "qiskit.passmanager.BasePassManager"), and individual flow controllers do not need to this method. For a flow controller, all the passes should be specificed in one go directly to the constructor.
* The general attribute and variable name `passes` is replaced with `tasks` all over the [`qiskit.passmanager`](/api/qiskit/0.45/passmanager#module-qiskit.passmanager "qiskit.passmanager") module. Note that a task must indicate a union of pass and controller, and the singular form pass conflicts with the Python keyword. In this sense, the use of tasks is much preferable.
* The [`Unroller`](/api/qiskit/0.45/qiskit.transpiler.passes.Unroller "qiskit.transpiler.passes.Unroller") transpiler pass has been deprecated and will be removed in a future release. The [`Unroller`](/api/qiskit/0.45/qiskit.transpiler.passes.Unroller "qiskit.transpiler.passes.Unroller") has been superseded by the [`BasisTranslator`](/api/qiskit/0.45/qiskit.transpiler.passes.BasisTranslator "qiskit.transpiler.passes.BasisTranslator") which provides a similar set of functionality but offers it in a more general manner so that you’re able to translate a circuit to any universal basis set. The [`Unroller`](/api/qiskit/0.45/qiskit.transpiler.passes.Unroller "qiskit.transpiler.passes.Unroller") class only works in situations where the circuit’s gate definitions are recursively defined in terms of the target basis; for Qiskit’s standard library gates this means [`UGate`](/api/qiskit/0.45/qiskit.circuit.library.UGate "qiskit.circuit.library.UGate") and [`CXGate`](/api/qiskit/0.45/qiskit.circuit.library.CXGate "qiskit.circuit.library.CXGate"). If you are using the [`Unroller`](/api/qiskit/0.45/qiskit.transpiler.passes.Unroller "qiskit.transpiler.passes.Unroller") pass it can be replaced by using a custom pass manager of the form:
```python
from qiskit.transpiler import PassManager
from qiskit.transpiler.passes import UnrollCustomDefinitions, BasisTranslator
from qiskit.circuit.equivalence_library import SessionEquivalenceLibrary as sel
pm = PassManager(
[
UnrollCustomDefinitions(sel, basis_gates=basis_gates),
BasisTranslator(sel, target_basis=basis_gates),
]
)
pm.run(circuit)
```
* The use of the value `"unroller"` for the `translation_method` keyword argument on the [`transpile()`](/api/qiskit/0.45/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") and [`generate_preset_pass_manager()`](/api/qiskit/0.45/transpiler_preset#qiskit.transpiler.preset_passmanagers.generate_preset_pass_manager "qiskit.transpiler.preset_passmanagers.generate_preset_pass_manager") has been deprecated. This translation stage plugin will be removed from Qiskit in a future release as it has been superseded by the default `"translator"` method which will work similarly to the `"unroller"` plugin but support a broader set of target backends.
<span id="relnotes-0-45-0-stable-0-45-visualization-deprecations" />
### Visualization Deprecations
* The default `matplotlib` drawer setting now issues a `FutureWarning`, as the default style is changing to the `"iqp"` style (previously known as `"iqx"`). The old default is available as the `"clifford"` style. To silence the warning, you can explicitly set the desired style, e.g.:
```python
from qiskit import QuantumCircuit
circuit = QuantumCircuit(2)
circuit.x(0)
circuit.h(0)
circuit.cp(0.5, 0, 1)
circuit.draw("mpl", style="clifford") # or style="iqp"
```
* Passing a circuit to [`qiskit.visualization.timeline_drawer()`](/api/qiskit/0.45/qiskit.visualization.timeline_drawer "qiskit.visualization.timeline_drawer") that does not have scheduled node start-time information is deprecated. Only circuits that have gone through one of the scheduling analysis passes (for example [`ALAPScheduleAnalysis`](/api/qiskit/0.45/qiskit.transpiler.passes.ALAPScheduleAnalysis "qiskit.transpiler.passes.ALAPScheduleAnalysis") or [`ASAPScheduleAnalysis`](/api/qiskit/0.45/qiskit.transpiler.passes.ASAPScheduleAnalysis "qiskit.transpiler.passes.ASAPScheduleAnalysis")) can be visualised. If you have used one of the old-style scheduling passes (for example [`ALAPSchedule`](/api/qiskit/0.45/qiskit.transpiler.passes.ALAPSchedule "qiskit.transpiler.passes.ALAPSchedule") or [`ASAPSchedule`](/api/qiskit/0.45/qiskit.transpiler.passes.ASAPSchedule "qiskit.transpiler.passes.ASAPSchedule")), you can propagate the scheduling information by running:
```python
from qiskit import transpile
from qiskit.transpiler import InstructionDurations
scheduled = transpile(
my_old_style_circuit,
optimization_level=0,
scheduling_method="alap",
instruction_durations=InstructionDurations(),
)
```
This behaviour was previously intended to be deprecated in Qiskit 0.37, but due to a bug in the warning, it was not displayed to users until now. The behaviour will be removed in Qiskit 1.0.
<span id="relnotes-0-45-0-stable-0-45-bug-fixes" />
<span id="id11" />
### Bug Fixes
* The maximum number of qubits to consider for matrix multiplication-based commutativity check in [`CommutationChecker`](/api/qiskit/0.45/qiskit.circuit.CommutationChecker "qiskit.circuit.CommutationChecker") is now limited to 3 by default. Fixed [#10488](https://github.com/Qiskit/qiskit/issues/10488)
* The [`GateDirection`](/api/qiskit/0.45/qiskit.transpiler.passes.GateDirection "qiskit.transpiler.passes.GateDirection") transpiler pass will now use discrete-basis translations rather than relying on a continuous [`RYGate`](/api/qiskit/0.45/qiskit.circuit.library.RYGate "qiskit.circuit.library.RYGate"), which should help make some discrete-basis-set targets slightly more reliable. In general, [`transpile()`](/api/qiskit/0.45/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") only has partial support for basis sets that do not contain a continuously-parametrised operation, and so it may not always succeed in these situations, and will almost certainly not produce optimal results.
* Fixed [`CommutationAnalysis`](/api/qiskit/0.45/qiskit.transpiler.passes.CommutationAnalysis "qiskit.transpiler.passes.CommutationAnalysis") to group gates on a wire into sets, with each set only containing gates that pairwise commute. This prevents `CommutationCancellation` from performing unsound optimizations. See [#8020](https://github.com/Qiskit/qiskit/issues/8020)
* [`CUGate`](/api/qiskit/0.45/qiskit.circuit.library.CUGate "qiskit.circuit.library.CUGate") will now behave correctly during calls to [`QuantumCircuit.assign_parameters()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#assign_parameters "qiskit.circuit.QuantumCircuit.assign_parameters"). Previously, it would cause various odd errors, often some time after the initial circuit assignment. See [#7326](https://github.com/Qiskit/qiskit/issues/7326), [#7410](https://github.com/Qiskit/qiskit/issues/7410), [#9627](https://github.com/Qiskit/qiskit/issues/9627), [#10002](https://github.com/Qiskit/qiskit/issues/10002), and [#10131](https://github.com/Qiskit/qiskit/issues/10131).
* The control-flow builder interface (the context-manager forms of [`QuantumCircuit.if_test()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#if_test "qiskit.circuit.QuantumCircuit.if_test"), [`while_loop()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#while_loop "qiskit.circuit.QuantumCircuit.while_loop"), [`for_loop()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#for_loop "qiskit.circuit.QuantumCircuit.for_loop") and [`switch()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#switch "qiskit.circuit.QuantumCircuit.switch")) will now correctly track a separate global-phase advancement within that block. You can add a global-phase advancement to an inner block by assigning to [`QuantumCircuit.global_phase`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#global_phase "qiskit.circuit.QuantumCircuit.global_phase") within a builder scope:
```python
from math import pi
from qiskit import QuantumCircuit
qc = QuantumCircuit(3, 3)
qc.global_phase = pi / 2 # Set the outer circuit's global phase.
with qc.if_test((qc.clbits[0], False)) as else_:
# The global phase advancement in a control-flow block begins at 0,
# because it represents how much the phase will be advanced by an
# execution of the block. The defined phase of the outer scope is not
# affected by this set.
qc.global_phase = pi
with else_:
# Similarly, the `else` block may induce a different global-phase
# advancement to the `if`, so it can also be set separately.
qc.global_phase = 1.5 * pi
# The phase advancement caused directly by the outer scope is independent
# of the phase advancement conditionally caused by each control-flow path.
assert qc.global_phase == pi / 2
```
The meaning of [`QuantumCircuit.global_phase`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#global_phase "qiskit.circuit.QuantumCircuit.global_phase") is taken to be the global-phase advancement that is inherent to a single execution of the block. It is still a *global* phase advancement, in that if the block is entered, the phase of all qubits in the entire program will be advanced.
* Fix the coloring of the `"iqx"` and `"iqx-dark"` matplotlib color schemes, which previously drew the [`RZGate`](/api/qiskit/0.45/qiskit.circuit.library.RZGate "qiskit.circuit.library.RZGate"), [`RZZGate`](/api/qiskit/0.45/qiskit.circuit.library.RZZGate "qiskit.circuit.library.RZZGate"), (multi-)controlled [`PhaseGate`](/api/qiskit/0.45/qiskit.circuit.library.PhaseGate "qiskit.circuit.library.PhaseGate")s and [`iSwapGate`](/api/qiskit/0.45/qiskit.circuit.library.iSwapGate "qiskit.circuit.library.iSwapGate") in the wrong color.
* The hash of a [`Parameter`](/api/qiskit/0.45/qiskit.circuit.Parameter "qiskit.circuit.Parameter") is now equal to the hashes of any [`ParameterExpression`](/api/qiskit/0.45/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression") that it compares equal to. Previously the hashes were different, which would cause spurious additional entries in hashmaps when [`Parameter`](/api/qiskit/0.45/qiskit.circuit.Parameter "qiskit.circuit.Parameter") and [`ParameterExpression`](/api/qiskit/0.45/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression") values were mixed in the same map as it violated Python’s data model.
* Fixed a bug in QPY serialization ([`qiskit.qpy`](/api/qiskit/0.45/qpy#module-qiskit.qpy "qiskit.qpy")) where controlled unitary gates in a circuit could result would fail to deserialize. Fixed [#10802](https://github.com/Qiskit/qiskit/issues/10802).
* Fixes the implementation of [`random_statevector()`](/api/qiskit/0.45/quantum_info#qiskit.quantum_info.random_statevector "qiskit.quantum_info.random_statevector") so that it samples from the uniform distribution.
* The pass [`NoiseAdaptiveLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.NoiseAdaptiveLayout "qiskit.transpiler.passes.NoiseAdaptiveLayout") now takes [`CouplingMap`](/api/qiskit/0.45/qiskit.transpiler.CouplingMap "qiskit.transpiler.CouplingMap") as an optional argument. This is used by the plugin to control on inconsistency between [`configuration()`](/api/qiskit/0.45/qiskit.providers.BackendV1#configuration "qiskit.providers.BackendV1.configuration") and [`properties()`](/api/qiskit/0.45/qiskit.providers.BackendV1#properties "qiskit.providers.BackendV1.properties"), like in the case of [`FakeMelbourne`](/api/qiskit/0.45/qiskit.providers.fake_provider.FakeMelbourne "qiskit.providers.fake_provider.FakeMelbourne"). Fixed [#7677](https://github.com/Qiskit/qiskit/issues/7677).
* The methods [`QuantumCircuit.copy()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#copy "qiskit.circuit.QuantumCircuit.copy") and [`copy_empty_like()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#copy_empty_like "qiskit.circuit.QuantumCircuit.copy_empty_like") will now raise an error if the `name` argument is incorrectly typed, instead of generating an invalid circuit.
* The `"decay"` heuristic of [`SabreSwap`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreSwap "qiskit.transpiler.passes.SabreSwap") and [`SabreLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.SabreLayout "qiskit.transpiler.passes.SabreLayout") now tracks the depth correctly on physical qubits rather than mistakenly tracking the “depth” of swaps on virtual qubits.
* Fixed an oversight in the [`ECRGate`](/api/qiskit/0.45/qiskit.circuit.library.ECRGate "qiskit.circuit.library.ECRGate") that prevented setting an [`ECRGate.label`](/api/qiskit/0.45/qiskit.circuit.library.ECRGate#label "qiskit.circuit.library.ECRGate.label") attribute at object construction time. All other [`Gate`](/api/qiskit/0.45/qiskit.circuit.Gate "qiskit.circuit.Gate") classes and subclasses enable setting a `label` keyword argument in the constructor.
* Fixed an oversight in the [`Gate`](/api/qiskit/0.45/qiskit.circuit.Gate "qiskit.circuit.Gate") (and standard-library subclasses) constructor where the [`duration`](/api/qiskit/0.45/qiskit.circuit.Gate#duration "qiskit.circuit.Gate.duration") and [`unit`](/api/qiskit/0.45/qiskit.circuit.Gate#unit "qiskit.circuit.Gate.unit") attributes could not be set as keyword arguments during construction. The parent class [`Instruction`](/api/qiskit/0.45/qiskit.circuit.Instruction "qiskit.circuit.Instruction") supported setting this but [`Gate`](/api/qiskit/0.45/qiskit.circuit.Gate "qiskit.circuit.Gate") was previously not exposing this interface correctly.
* Added support to allow `SparsePauliOp` default initialization passing an empty iterable to the static methods [`from_list()`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp#from_list "qiskit.quantum_info.SparsePauliOp.from_list") and [`from_sparse_list()`](/api/qiskit/0.45/qiskit.quantum_info.SparsePauliOp#from_sparse_list "qiskit.quantum_info.SparsePauliOp.from_sparse_list"). Fixed [#10159](https://github.com/Qiskit/qiskit/issues/10159).
* The use of the (deprecated) `Optimizer` class on [`AQC`](/api/qiskit/0.45/qiskit.transpiler.synthesis.aqc.AQC "qiskit.transpiler.synthesis.aqc.AQC") did not have a non-deprecated alternative path, which should have been introduced in Qiskit 0.44. It now accepts a callable that implements the [`Minimizer`](/api/qiskit/0.45/qiskit.algorithms.optimizers.Minimizer "qiskit.algorithms.optimizers.Minimizer") protocol, as explicitly stated in the deprecation warning. The callable can look like the following example:
> ```python
> from scipy.optimize import minimize
> from qiskit.transpiler.synthesis.aqc.aqc import AQC
>
> optimizer = partial(minimize, args=(), method="L-BFGS-B", options={"maxiter": 200})
> aqc = AQC(optimizer=optimizer)
> ```
* Fixed an issue with the [`Barrier`](/api/qiskit/0.45/qiskit.circuit.library.Barrier "qiskit.circuit.library.Barrier") class. When adding a [`Barrier`](/api/qiskit/0.45/qiskit.circuit.library.Barrier "qiskit.circuit.library.Barrier") instance to a [`QuantumCircuit`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") with the [`QuantumCircuit.append()`](/api/qiskit/0.45/qiskit.circuit.QuantumCircuit#append "qiskit.circuit.QuantumCircuit.append") method previously there was no validation that the size of the barrier matched the qargs specified.
* The `BlockCollapser` transpiler pass will now correctly handle circuits that contain more than one condition on the same classical register.
* `BlueprintCircuit` subclasses will now behave correctly when the semi-public method `QuantumCircuit._append()` is used with the blueprint in an unbuilt state, *i.e.* the circuit will be built before attempting the append.
* Adjusted zoom, fontsize, and margins in [`plot_state_city()`](/api/qiskit/0.45/qiskit.visualization.plot_state_city "qiskit.visualization.plot_state_city") to fit the plot better for more figure sizes. Corrected the Z-ordering behavior of bars and the zero-amplitude plane, and corrected display of negative real value bars.
<span id="relnotes-0-45-0-stable-0-45-other-notes" />
### Other Notes
* This version of Qiskit is explicitly pinned to the Numpy 1.x series, because it includes compiled extensions that are not yet compiled against the as-yet-unreleased Numpy 2.x series. We will release a new version of Qiskit with Numpy 2.x support as soon as feasible.
We cannot prevent your package manager from resolving to older versions of Qiskit (which do not have the same pin but are still likely to be incompatible) if you forcibly try to install Qiskit alongside Numpy 2, before we have released a compatible version.
* Modified the behavior of the [`VF2Layout`](/api/qiskit/0.45/qiskit.transpiler.passes.VF2Layout "qiskit.transpiler.passes.VF2Layout") and [`VF2PostLayout`](/api/qiskit/0.45/qiskit.transpiler.passes.VF2PostLayout "qiskit.transpiler.passes.VF2PostLayout") transpiler passes, which would previously run their internal scoring using multithreading if the input circuits were sufficiently large. The multithreading usage has now been removed from the passes, as it was shown to cause a performance regression instead of an improvement like originally intended.
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