113 lines
6.1 KiB
Plaintext
113 lines
6.1 KiB
Plaintext
---
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title: classicalfunction (v1.4)
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description: API reference for qiskit.circuit.classicalfunction in qiskit v1.4
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in_page_toc_min_heading_level: 2
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python_api_type: module
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python_api_name: qiskit.circuit.classicalfunction
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---
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<span id="module-qiskit.circuit.classicalfunction" />
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<span id="qiskit-circuit-classicalfunction" />
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<span id="classicalfunction-compiler-qiskit-circuit-classicalfunction" />
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# ClassicalFunction compiler
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`qiskit.circuit.classicalfunction`
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## Overview
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<Admonition title="Warning" type="caution">
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This module is deprecated as of Qiskit 1.4.0. It will be removed in the Qiskit 2.0 release.
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</Admonition>
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The classical function compiler provides the necessary tools to map a classical potentially irreversible functions into quantum circuits. Below is a simple example of how to synthesize a simple boolean function defined using Python into a QuantumCircuit:
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> ```python
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> from qiskit.circuit.classicalfunction import classical_function
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> from qiskit.circuit.classicalfunction.types import Int1
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>
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> @classical_function
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> def grover_oracle(a: Int1, b: Int1, c: Int1, d: Int1) -> Int1:
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> return (not a and b and not c and d)
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>
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> quantum_circuit = grover_oracle.synth(registerless=False)
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> quantum_circuit.draw('text')
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>
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> a: ──o──
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> │
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> b: ──■──
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> │
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> c: ──o──
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> │
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> d: ──■──
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> ┌─┴─┐
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> return: ┤ X ├
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> └───┘
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> ```
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Following Qiskit’s little-endian bit ordering convention, the left-most bit (`a`) is the most significant bit and the right-most bit (`d`) is the least significant bit.
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<Admonition title="Warning" type="caution">
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The functionality of qiskit.circuit.classicalfunction requires tweedledum, which isn’t available on all platforms (up to Python version 3.11). See [tweedledum installation guide](https://github.com/boschmitt/tweedledum/tree/master?tab=readme-ov-file#installation) for more details.
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</Admonition>
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## Supplementary Information
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### Tweedledum
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Tweedledum is a C++-17 header-only library that implements a large set of reversible (and quantum) synthesis, optimization, and mapping algorithms. The classical function compiler relies on it and its dependencies to both represent logic networks and synthesize them into quantum circuits.
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### ClassicalFunction data types
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At the moment, the only type supported by the classical\_function compilers is `qiskit.circuit.classicalfunction.types.Int1`. The classical function function to parse *must* include type hints (just `Int1` for now). The resulting gate will be a gate in the size of the sum of all the parameters and the return.
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The type `Int1` means the classical function will only operate at bit level.
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## ClassicalFunction compiler API
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<span id="classical-function" />
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### classical\_function
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Decorator for a classical function that returns a ClassicalFunction object.
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#### classical\_function
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<Function id="qiskit.circuit.classicalfunction.classical_function" github="https://github.com/Qiskit/qiskit/tree/stable/1.4/qiskit/circuit/classicalfunction/__init__.py#L128-L152" signature="qiskit.circuit.classicalfunction.classical_function(func)">
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Parses and type checks the callable `func` to compile it into an `ClassicalFunction` that can be synthesized into a `QuantumCircuit`.
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<Admonition title="Deprecated since version 1.4" type="danger">
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The function `qiskit.circuit.classicalfunction.classical_function()` is deprecated as of qiskit 1.4. It will be removed in Qiskit 2.0. Use PhaseOracle instead, which can be turned into a bit-flip oracle by applying Hadamard gates on the target qubit before and after the instruction, and conditioning.the instruction on the target qubit.
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</Admonition>
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**Parameters**
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**func** (*callable*) – A callable (with type hints) to compile into an `ClassicalFunction`.
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**Returns**
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An object that can synthesis into a QuantumCircuit (via `synth()` method).
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**Return type**
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[ClassicalFunction](qiskit.circuit.classicalfunction.ClassicalFunction "qiskit.circuit.classicalfunction.ClassicalFunction")
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</Function>
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### ClassicalFunction
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| | |
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| --------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------- |
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| [`ClassicalFunction`](qiskit.circuit.classicalfunction.ClassicalFunction "qiskit.circuit.classicalfunction.ClassicalFunction")(source\[, name]) | Represent a classical function and its logic network. |
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| [`BooleanExpression`](qiskit.circuit.classicalfunction.BooleanExpression "qiskit.circuit.classicalfunction.BooleanExpression")(expression\[, name, var\_order]) | The Boolean Expression gate. |
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### Exceptions
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| -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------- |
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| [`ClassicalFunctionCompilerTypeError`](qiskit.circuit.classicalfunction.ClassicalFunctionCompilerTypeError "qiskit.circuit.classicalfunction.ClassicalFunctionCompilerTypeError")(\*message) | ClassicalFunction compiler type error. |
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| [`ClassicalFunctionParseError`](qiskit.circuit.classicalfunction.ClassicalFunctionParseError "qiskit.circuit.classicalfunction.ClassicalFunctionParseError")(\*message) | ClassicalFunction compiler parse error. |
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| [`ClassicalFunctionCompilerTypeError`](qiskit.circuit.classicalfunction.ClassicalFunctionCompilerTypeError "qiskit.circuit.classicalfunction.ClassicalFunctionCompilerTypeError")(\*message) | ClassicalFunction compiler type error. |
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