129 lines
5.0 KiB
Plaintext
129 lines
5.0 KiB
Plaintext
---
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title: NumPyEigensolver (v0.31)
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description: API reference for qiskit.aqua.algorithms.NumPyEigensolver in qiskit v0.31
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.aqua.algorithms.NumPyEigensolver
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---
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# NumPyEigensolver
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<Class id="qiskit.aqua.algorithms.NumPyEigensolver" isDedicatedPage={true} github="https://github.com/qiskit-community/qiskit-aqua/tree/stable/0.9/qiskit/aqua/algorithms/eigen_solvers/numpy_eigen_solver.py" signature="NumPyEigensolver(operator=None, k=1, aux_operators=None, filter_criterion=None)" modifiers="class">
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Bases: `qiskit.aqua.algorithms.classical_algorithm.ClassicalAlgorithm`, `qiskit.aqua.algorithms.eigen_solvers.eigen_solver.Eigensolver`
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The NumPy Eigensolver algorithm.
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NumPy Eigensolver computes up to the first $k$ eigenvalues of a complex-valued square matrix of dimension $n \times n$, with $k \leq n$.
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<Admonition title="Note" type="note">
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Operators are automatically converted to `MatrixOperator` as needed and this conversion can be costly in terms of memory and performance as the operator size, mostly in terms of number of qubits it represents, gets larger.
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</Admonition>
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**Parameters**
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* **operator** (`Union`\[`OperatorBase`, `LegacyBaseOperator`, `None`]) – Operator instance. If None is supplied it must be provided later before run() is called. Allowing None here permits the algorithm to be configured and used later when operator is available, say creating an instance an letting application stack use this algorithm with an operator it creates.
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* **k** (`int`) – How many eigenvalues are to be computed, has a min. value of 1.
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* **aux\_operators** (`Optional`\[`List`\[`Union`\[`OperatorBase`, `LegacyBaseOperator`, `None`]]]) – Auxiliary operators to be evaluated at each eigenvalue
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* **filter\_criterion** (`Optional`\[`Callable`\[\[`Union`\[`List`, `ndarray`], `float`, `Optional`\[`List`\[`float`]]], `bool`]]) – callable that allows to filter eigenvalues/eigenstates, only feasible eigenstates are returned in the results. The callable has the signature filter(eigenstate, eigenvalue, aux\_values) and must return a boolean to indicate whether to keep this value in the final returned result or not. If the number of elements that satisfies the criterion is smaller than k then the returned list has fewer elements and can even be empty.
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## Methods
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<span id="qiskit-aqua-algorithms-numpyeigensolver-compute-eigenvalues" />
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### compute\_eigenvalues
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<Function id="qiskit.aqua.algorithms.NumPyEigensolver.compute_eigenvalues" signature="NumPyEigensolver.compute_eigenvalues(operator=None, aux_operators=None)">
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Computes eigenvalues. Operator and aux\_operators can be supplied here and if not None will override any already set into algorithm so it can be reused with different operators. While an operator is required by algorithms, aux\_operators are optional. To ‘remove’ a previous aux\_operators array use an empty list here.
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**Parameters**
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* **operator** (`Union`\[`OperatorBase`, `LegacyBaseOperator`, `None`]) – If not None replaces operator in algorithm
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* **aux\_operators** (`Optional`\[`List`\[`Union`\[`OperatorBase`, `LegacyBaseOperator`, `None`]]]) – If not None replaces aux\_operators in algorithm
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**Return type**
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`EigensolverResult`
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**Returns**
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EigensolverResult
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</Function>
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<span id="qiskit-aqua-algorithms-numpyeigensolver-run" />
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### run
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<Function id="qiskit.aqua.algorithms.NumPyEigensolver.run" signature="NumPyEigensolver.run()">
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Execute the classical algorithm.
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**Returns**
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results of an algorithm.
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**Return type**
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dict
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</Function>
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<span id="qiskit-aqua-algorithms-numpyeigensolver-supports-aux-operators" />
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### supports\_aux\_operators
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<Function id="qiskit.aqua.algorithms.NumPyEigensolver.supports_aux_operators" signature="NumPyEigensolver.supports_aux_operators()" modifiers="classmethod">
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Whether computing the expectation value of auxiliary operators is supported.
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**Return type**
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`bool`
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**Returns**
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True if aux\_operator expectations can be evaluated, False otherwise
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</Function>
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## Attributes
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### aux\_operators
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<Attribute id="qiskit.aqua.algorithms.NumPyEigensolver.aux_operators">
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**Return type**
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`Optional`\[`List`\[`Optional`\[`OperatorBase`]]]
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</Attribute>
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### filter\_criterion
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<Attribute id="qiskit.aqua.algorithms.NumPyEigensolver.filter_criterion">
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returns the filter criterion if set
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**Return type**
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`Optional`\[`Callable`\[\[`Union`\[`List`, `ndarray`], `float`, `Optional`\[`List`\[`float`]]], `bool`]]
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</Attribute>
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### k
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<Attribute id="qiskit.aqua.algorithms.NumPyEigensolver.k">
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returns k (number of eigenvalues requested)
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**Return type**
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`int`
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</Attribute>
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### operator
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<Attribute id="qiskit.aqua.algorithms.NumPyEigensolver.operator">
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**Return type**
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`Optional`\[`OperatorBase`]
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</Attribute>
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### random
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<Attribute id="qiskit.aqua.algorithms.NumPyEigensolver.random">
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Return a numpy random.
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</Attribute>
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</Class>
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