---
title: MCXSynthesisDefault (latest version)
description: API reference for qiskit.transpiler.passes.synthesis.hls_plugins.MCXSynthesisDefault in the latest version of qiskit
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/qiskit.transpiler.passes.synthesis.hls_plugins.MCXSynthesisDefault
---

# MCXSynthesisDefault

*class* `qiskit.transpiler.passes.synthesis.hls_plugins.MCXSynthesisDefault`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.5/qiskit/transpiler/passes/synthesis/hls_plugins.py#L1485-L1556)

Bases: [`HighLevelSynthesisPlugin`](/docs/api/qiskit/qiskit.transpiler.passes.synthesis.plugin.HighLevelSynthesisPlugin "qiskit.transpiler.passes.synthesis.plugin.HighLevelSynthesisPlugin")

The default synthesis plugin for a multi-controlled X gate.

This plugin name is :`mcx.default` which can be used as the key on an [`HLSConfig`](/docs/api/qiskit/qiskit.transpiler.passes.HLSConfig "qiskit.transpiler.passes.HLSConfig") object to use this method with [`HighLevelSynthesis`](/docs/api/qiskit/qiskit.transpiler.passes.HighLevelSynthesis "qiskit.transpiler.passes.HighLevelSynthesis").

The plugin supports the following plugin-specific options:

- `optimization_metric`: The optimization metric, indicating the property of the output circuit (e.g., the 2-qubit gate count or the T-count) that should be minimized. See [`OptimizationMetric`](/docs/api/qiskit/qiskit.transpiler.OptimizationMetric "qiskit.transpiler.OptimizationMetric").
- `num_clean_ancillas`: The number of clean ancillary qubits available.
- `num_dirty_ancillas`: The number of dirty ancillary qubits available.

## Methods

### run

`run(high_level_object, coupling_map=None, target=None, qubits=None, **options)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/2.5/qiskit/transpiler/passes/synthesis/hls_plugins.py#L1502-L1556)

Run synthesis for the given MCX gate.