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---
title: compiler (dev version)
description: API reference for qiskit.compiler in the dev version of qiskit
in_page_toc_min_heading_level: 2
python_api_type: module
python_api_name: qiskit.compiler
---
<span id="module-qiskit.compiler" />
<span id="qiskit-compiler" />
<span id="compilation-routines-qiskit-compiler" />
# Compilation Routines
`qiskit.compiler`
## Circuit Compilation Functions
### transpile
<Function id="qiskit.compiler.transpile" github="https://github.com/Qiskit/qiskit/tree/main/qiskit/compiler/transpiler.py#L36-L300" signature="qiskit.compiler.transpile(circuits, backend=None, basis_gates=None, coupling_map=None, initial_layout=None, layout_method=None, routing_method=None, translation_method=None, scheduling_method=None, dt=None, approximation_degree=1.0, seed_transpiler=None, optimization_level=None, callback=None, output_name=None, unitary_synthesis_method='default', unitary_synthesis_plugin_config=None, target=None, hls_config=None, init_method=None, optimization_method=None, ignore_backend_supplied_default_methods=False, num_processes=None, qubits_initially_zero=True)">
Transpile one or more circuits, according to some desired transpilation targets.
Transpilation is potentially done in parallel using multiprocessing when `circuits` is a list with > 1 [`QuantumCircuit`](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit") object, depending on the local environment and configuration.
The prioritization of transpilation target constraints works as follows: if a `target` input is provided, it will take priority over any `backend` input or loose constraints (`basis_gates`, `coupling_map`, or `dt`). If a `backend` is provided together with any loose constraint from the list above, the loose constraint will take priority over the corresponding backend constraint. This behavior is summarized in the table below. The first column in the table summarizes the potential user-provided constraints, and each cell shows whether the priority is assigned to that specific constraint input or another input (target/backend(V2)).
| User Provided | target | backend(V2) |
| ----------------- | ------ | ------------- |
| **basis\_gates** | target | basis\_gates |
| **coupling\_map** | target | coupling\_map |
| **dt** | target | dt |
**Parameters**
* **circuits** (*\_CircuitT*) – Circuit(s) to transpile
* **backend** ([*Backend*](qiskit.providers.Backend "qiskit.providers.backend.Backend") *| None*) – If set, the transpiler will compile the input circuit to this target device. If any other option is explicitly set (e.g., `coupling_map`), it will override the backend’s.
* **basis\_gates** ([*List*](https://docs.python.org/3/library/typing.html#typing.List "(in Python v3.13)")*\[*[*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")*] | None*) – List of basis gate names to unroll to (e.g: `['u1', 'u2', 'u3', 'cx']`). If `None`, do not unroll.
* **coupling\_map** ([*CouplingMap*](qiskit.transpiler.CouplingMap "qiskit.transpiler.coupling.CouplingMap") *|*[*List*](https://docs.python.org/3/library/typing.html#typing.List "(in Python v3.13)")*\[*[*List*](https://docs.python.org/3/library/typing.html#typing.List "(in Python v3.13)")*\[*[*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")*]] | None*) –
Directed coupling map (perhaps custom) to target in mapping. If the coupling map is symmetric, both directions need to be specified.
Multiple formats are supported:
1. `CouplingMap` instance
2. List, must be given as an adjacency matrix, where each entry specifies all directed two-qubit interactions supported by backend, e.g: `[[0, 1], [0, 3], [1, 2], [1, 5], [2, 5], [4, 1], [5, 3]]`
* **initial\_layout** ([*Layout*](qiskit.transpiler.Layout "qiskit.transpiler.layout.Layout") *|*[*Dict*](https://docs.python.org/3/library/typing.html#typing.Dict "(in Python v3.13)") *|*[*List*](https://docs.python.org/3/library/typing.html#typing.List "(in Python v3.13)") *| None*) –
Initial position of virtual qubits on physical qubits. If this layout makes the circuit compatible with the coupling\_map constraints, it will be used. The final layout is not guaranteed to be the same, as the transpiler may permute qubits through swaps or other means. Multiple formats are supported:
1. `Layout` instance
2. Dict \* virtual to physical:
```python
{qr[0]: 0,
qr[1]: 3,
qr[2]: 5}
```
* physical to virtual:
```python
{0: qr[0],
3: qr[1],
5: qr[2]}
```
3. List
* virtual to physical:
```python
[0, 3, 5] # virtual qubits are ordered (in addition to named)
```
* physical to virtual:
```python
[qr[0], None, None, qr[1], None, qr[2]]
```
* **layout\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *| None*) – Name of layout selection pass (‘trivial’, ‘dense’, ‘sabre’). This can also be the external plugin name to use for the `layout` stage. You can see a list of installed plugins by using [`list_stage_plugins()`](transpiler_plugins#qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins") with `"layout"` for the `stage_name` argument.
* **routing\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *| None*) – Name of routing pass (‘basic’, ‘lookahead’, ‘stochastic’, ‘sabre’, ‘none’). Note This can also be the external plugin name to use for the `routing` stage. You can see a list of installed plugins by using [`list_stage_plugins()`](transpiler_plugins#qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins") with `"routing"` for the `stage_name` argument.
* **translation\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *| None*) – Name of translation pass (`"default"`, `"translator"` or `"synthesis"`). This can also be the external plugin name to use for the `translation` stage. You can see a list of installed plugins by using [`list_stage_plugins()`](transpiler_plugins#qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins") with `"translation"` for the `stage_name` argument.
* **scheduling\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *| None*) – Name of scheduling pass. \* `'as_soon_as_possible'`: Schedule instructions greedily, as early as possible on a qubit resource. (alias: `'asap'`) \* `'as_late_as_possible'`: Schedule instructions late, i.e. keeping qubits in the ground state when possible. (alias: `'alap'`) If `None`, no scheduling will be done. This can also be the external plugin name to use for the `scheduling` stage. You can see a list of installed plugins by using [`list_stage_plugins()`](transpiler_plugins#qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins") with `"scheduling"` for the `stage_name` argument.
* **dt** ([*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.13)") *| None*) – Backend sample time (resolution) in seconds. If `None` (default), `backend.dt` is used.
* **approximation\_degree** ([*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.13)")) – heuristic dial used for circuit approximation (1.0=no approximation, 0.0=maximal approximation)
* **seed\_transpiler** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)") *| None*) – Sets random seed for the stochastic parts of the transpiler
* **optimization\_level** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)") *| None*) –
How much optimization to perform on the circuits. Higher levels generate more optimized circuits, at the expense of longer transpilation time.
* 0: no optimization
* 1: light optimization
* 2: heavy optimization
* 3: even heavier optimization
If `None`, level 2 will be chosen as default.
* **callback** ([*Callable*](https://docs.python.org/3/library/typing.html#typing.Callable "(in Python v3.13)")*\[\[BasePass,* [*DAGCircuit*](qiskit.dagcircuit.DAGCircuit "qiskit._accelerate.circuit.DAGCircuit")*,* [*float*](https://docs.python.org/3/library/functions.html#float "(in Python v3.13)")*,* [*PropertySet*](qiskit.passmanager.PropertySet "qiskit.passmanager.compilation_status.PropertySet")*,* [*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")*],* [*Any*](https://docs.python.org/3/library/typing.html#typing.Any "(in Python v3.13)")*] | None*) –
A callback function that will be called after each pass execution. The function will be called with 5 keyword arguments, | `pass_`: the pass being run. | `dag`: the dag output of the pass. | `time`: the time to execute the pass. | `property_set`: the property set. | `count`: the index for the pass execution. The exact arguments passed expose the internals of the pass manager, and are subject to change as the pass manager internals change. If you intend to reuse a callback function over multiple releases, be sure to check that the arguments being passed are the same. To use the callback feature, define a function that will take in kwargs dict and access the variables. For example:
```python
def callback_func(**kwargs):
pass_ = kwargs['pass_']
dag = kwargs['dag']
time = kwargs['time']
property_set = kwargs['property_set']
count = kwargs['count']
...
transpile(circ, callback=callback_func)
```
* **output\_name** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *|*[*List*](https://docs.python.org/3/library/typing.html#typing.List "(in Python v3.13)")*\[*[*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")*] | None*) – A list with strings to identify the output circuits. The length of the list should be exactly the length of the `circuits` parameter.
* **unitary\_synthesis\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) – The name of the unitary synthesis method to use. By default `'default'` is used. You can see a list of installed plugins with [`unitary_synthesis_plugin_names()`](qiskit.transpiler.passes.synthesis.plugin.unitary_synthesis_plugin_names "qiskit.transpiler.passes.synthesis.plugin.unitary_synthesis_plugin_names").
* **unitary\_synthesis\_plugin\_config** ([*dict*](https://docs.python.org/3/library/stdtypes.html#dict "(in Python v3.13)") *| None*) – An optional configuration dictionary that will be passed directly to the unitary synthesis plugin. By default this setting will have no effect as the default unitary synthesis method does not take custom configuration. This should only be necessary when a unitary synthesis plugin is specified with the `unitary_synthesis_method` argument. As this is custom for each unitary synthesis plugin refer to the plugin documentation for how to use this option.
* **target** ([*Target*](qiskit.transpiler.Target "qiskit.transpiler.target.Target") *| None*) – A backend transpiler target. Normally this is specified as part of the `backend` argument, but if you have manually constructed a [`Target`](qiskit.transpiler.Target "qiskit.transpiler.Target") object you can specify it manually here. This will override the target from `backend`.
* **hls\_config** ([*HLSConfig*](qiskit.transpiler.passes.HLSConfig "qiskit.transpiler.passes.synthesis.high_level_synthesis.HLSConfig") *| None*) – An optional configuration class `HLSConfig` that will be passed directly to `HighLevelSynthesis` transformation pass. This configuration class allows to specify for various high-level objects the lists of synthesis algorithms and their parameters.
* **init\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *| None*) – The plugin name to use for the `init` stage. By default an external plugin is not used. You can see a list of installed plugins by using [`list_stage_plugins()`](transpiler_plugins#qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins") with `"init"` for the stage name argument.
* **optimization\_method** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *| None*) – The plugin name to use for the `optimization` stage. By default an external plugin is not used. You can see a list of installed plugins by using [`list_stage_plugins()`](transpiler_plugins#qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins "qiskit.transpiler.preset_passmanagers.plugin.list_stage_plugins") with `"optimization"` for the `stage_name` argument.
* **ignore\_backend\_supplied\_default\_methods** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")) – If set to `True` any default methods specified by a backend will be ignored. Some backends specify alternative default methods to support custom compilation target-specific passes/plugins which support backend-specific compilation techniques. If you’d prefer that these defaults were not used this option is used to disable those backend-specific defaults.
* **num\_processes** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)") *| None*) – The maximum number of parallel processes to launch for this call to transpile if parallel execution is enabled. This argument overrides `num_processes` in the user configuration file, and the `QISKIT_NUM_PROCS` environment variable. If set to `None` the system default or local user configuration will be used.
* **qubits\_initially\_zero** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")) – Indicates whether the input circuit is zero-initialized.
**Returns**
The transpiled circuit(s).
**Raises**
[**TranspilerError**](transpiler#qiskit.transpiler.TranspilerError "qiskit.transpiler.TranspilerError") – in case of bad inputs to transpiler (like conflicting parameters) or errors in passes
**Return type**
*\_CircuitT*
</Function>
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