118 lines
5.1 KiB
Plaintext
118 lines
5.1 KiB
Plaintext
---
|
||
title: NaturalGradient
|
||
description: API reference for qiskit.opflow.gradients.NaturalGradient
|
||
in_page_toc_min_heading_level: 1
|
||
python_api_type: class
|
||
python_api_name: qiskit.opflow.gradients.NaturalGradient
|
||
---
|
||
|
||
# NaturalGradient
|
||
|
||
<Class id="qiskit.opflow.gradients.NaturalGradient" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.24/qiskit/opflow/gradients/natural_gradient.py" signature="NaturalGradient(grad_method='lin_comb', qfi_method='lin_comb_full', regularization=None, **kwargs)" modifiers="class">
|
||
Bases: [`GradientBase`](qiskit.opflow.gradients.GradientBase "qiskit.opflow.gradients.gradient_base.GradientBase")
|
||
|
||
Deprecated: Convert an operator expression to the first-order gradient.
|
||
|
||
Given an ill-posed inverse problem
|
||
|
||
> x = arg min\{||Ax-C||^2} (1)
|
||
|
||
one can use regularization schemes can be used to stabilize the system and find a numerical solution
|
||
|
||
> x\_lambda = arg min\{||Ax-C||^2 + lambda\*R(x)} (2)
|
||
|
||
where R(x) represents the penalization term.
|
||
|
||
<Admonition title="Deprecated since version 0.24.0" type="danger">
|
||
The class `qiskit.opflow.gradients.natural_gradient.NaturalGradient` is deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. For code migration guidelines, visit [https://qisk.it/opflow\_migration](https://qisk.it/opflow_migration).
|
||
</Admonition>
|
||
|
||
**Parameters**
|
||
|
||
* **grad\_method** (*str |* [*CircuitGradient*](qiskit.opflow.gradients.CircuitGradient "qiskit.opflow.gradients.circuit_gradients.circuit_gradient.CircuitGradient")) – The method used to compute the state gradient. Can be either `'param_shift'` or `'lin_comb'` or `'fin_diff'`.
|
||
* **qfi\_method** (*str |* [*CircuitQFI*](qiskit.opflow.gradients.CircuitQFI "qiskit.opflow.gradients.circuit_qfis.circuit_qfi.CircuitQFI")) – The method used to compute the QFI. Can be either `'lin_comb_full'` or `'overlap_block_diag'` or `'overlap_diag'`.
|
||
* **regularization** (*str | None*) – Use the following regularization with a least square method to solve the underlying system of linear equations Can be either None or `'ridge'` or `'lasso'` or `'perturb_diag'` `'ridge'` and `'lasso'` use an automatic optimal parameter search If regularization is None but the metric is ill-conditioned or singular then a least square solver is used without regularization
|
||
* **kwargs** (*dict*) – Optional parameters for a CircuitGradient
|
||
|
||
## Methods Defined Here
|
||
|
||
<span id="qiskit-opflow-gradients-naturalgradient-convert" />
|
||
|
||
### convert
|
||
|
||
<Function id="qiskit.opflow.gradients.NaturalGradient.convert" signature="NaturalGradient.convert(operator, params=None)">
|
||
**Parameters**
|
||
|
||
* **operator** ([*OperatorBase*](qiskit.opflow.OperatorBase "qiskit.opflow.operator_base.OperatorBase")) – The operator we are taking the gradient of.
|
||
* **params** ([*ParameterVector*](qiskit.circuit.ParameterVector "qiskit.circuit.parametervector.ParameterVector") *|*[*ParameterExpression*](qiskit.circuit.ParameterExpression "qiskit.circuit.parameterexpression.ParameterExpression") *| List\[*[*ParameterExpression*](qiskit.circuit.ParameterExpression "qiskit.circuit.parameterexpression.ParameterExpression")*] | None*) – The parameters we are taking the gradient with respect to. If not explicitly passed, they are inferred from the operator and sorted by name.
|
||
|
||
**Returns**
|
||
|
||
An operator whose evaluation yields the NaturalGradient.
|
||
|
||
**Raises**
|
||
|
||
* **TypeError** – If `operator` does not represent an expectation value or the quantum state is not `CircuitStateFn`.
|
||
* **ValueError** – If `params` contains a parameter not present in `operator`.
|
||
* **ValueError** – If `operator` is not parameterized.
|
||
|
||
**Return type**
|
||
|
||
[*OperatorBase*](qiskit.opflow.OperatorBase "qiskit.opflow.operator_base.OperatorBase")
|
||
</Function>
|
||
|
||
<span id="qiskit-opflow-gradients-naturalgradient-nat-grad-combo-fn" />
|
||
|
||
### nat\_grad\_combo\_fn
|
||
|
||
<Function id="qiskit.opflow.gradients.NaturalGradient.nat_grad_combo_fn" signature="NaturalGradient.nat_grad_combo_fn(x, regularization=None)" modifiers="static">
|
||
Natural Gradient Function Implementation.
|
||
|
||
**Parameters**
|
||
|
||
* **x** (*tuple*) – Iterable consisting of Gradient, Quantum Fisher Information.
|
||
* **regularization** (*str | None*) – Regularization method.
|
||
|
||
**Returns**
|
||
|
||
Natural Gradient.
|
||
|
||
**Raises**
|
||
|
||
**ValueError** – If the gradient has imaginary components that are non-negligible.
|
||
|
||
**Return type**
|
||
|
||
[*ndarray*](https://numpy.org/doc/stable/reference/generated/numpy.ndarray.html#numpy.ndarray "(in NumPy v1.25)")
|
||
</Function>
|
||
|
||
## Attributes
|
||
|
||
### grad\_method
|
||
|
||
<Attribute id="qiskit.opflow.gradients.NaturalGradient.grad_method">
|
||
Returns `CircuitGradient`.
|
||
|
||
**Returns**
|
||
|
||
`CircuitGradient`.
|
||
</Attribute>
|
||
|
||
### qfi\_method
|
||
|
||
<Attribute id="qiskit.opflow.gradients.NaturalGradient.qfi_method">
|
||
Returns `CircuitQFI`.
|
||
|
||
Returns: `CircuitQFI`.
|
||
</Attribute>
|
||
|
||
### regularization
|
||
|
||
<Attribute id="qiskit.opflow.gradients.NaturalGradient.regularization">
|
||
Returns the regularization option.
|
||
|
||
Returns: the regularization option.
|
||
</Attribute>
|
||
</Class>
|
||
|