114 lines
4.6 KiB
Plaintext
114 lines
4.6 KiB
Plaintext
---
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title: BaseQGT
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description: API reference for qiskit.algorithms.gradients.BaseQGT
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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.algorithms.gradients.BaseQGT
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---
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# BaseQGT
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<Class id="qiskit.algorithms.gradients.BaseQGT" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.23/qiskit/algorithms/gradients/base_qgt.py" signature="BaseQGT(estimator, phase_fix=True, derivative_type=DerivativeType.COMPLEX, options=None)" modifiers="class">
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Bases: `abc.ABC`
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Base class to computes the Quantum Geometric Tensor (QGT) given a pure, parameterized quantum state. QGT is defined as:
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$$
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\mathrm{QGT}_{ij}= \langle \partial_i \psi | \partial_j \psi \rangle
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- \langle\partial_i \psi | \psi \rangle \langle\psi | \partial_j \psi \rangle.
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$$
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**Parameters**
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* **estimator** ([*BaseEstimator*](qiskit.primitives.BaseEstimator "qiskit.primitives.BaseEstimator")) – The estimator used to compute the QGT.
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* **phase\_fix** (*bool*) – Whether to calculate the second term (phase fix) of the QGT, which is $\langle\partial_i \psi | \psi \rangle \langle\psi | \partial_j \psi \rangle$. Defaults to `True`.
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* **derivative\_type** ([*DerivativeType*](qiskit.algorithms.gradients.DerivativeType "qiskit.algorithms.gradients.DerivativeType")) –
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The type of derivative. Can be either `DerivativeType.REAL` `DerivativeType.IMAG`, or `DerivativeType.COMPLEX`. Defaults to `DerivativeType.REAL`.
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* `DerivativeType.REAL` computes
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$$
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\mathrm{Re(QGT)}_{ij}= \mathrm{Re}[\langle \partial_i \psi | \partial_j \psi \rangle
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- \langle\partial_i \psi | \psi \rangle \langle\psi | \partial_j \psi \rangle].
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$$
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* `DerivativeType.IMAG` computes
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$$
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\mathrm{Im(QGT)}_{ij}= \mathrm{Im}[\langle \partial_i \psi | \partial_j \psi \rangle
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- \langle\partial_i \psi | \psi \rangle \langle\psi | \partial_j \psi \rangle].
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$$
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* `DerivativeType.COMPLEX` computes
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$$
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\mathrm{QGT}_{ij}= [\langle \partial_i \psi | \partial_j \psi \rangle
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- \langle\partial_i \psi | \psi \rangle \langle\psi | \partial_j \psi \rangle].
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$$
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* **options** ([*Options*](qiskit.providers.Options "qiskit.providers.Options") *| None*) – Backend runtime options used for circuit execution. The order of priority is: options in `run` method > QGT’s default options > primitive’s default setting. Higher priority setting overrides lower priority setting.
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## Methods
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### run
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<Function id="qiskit.algorithms.gradients.BaseQGT.run" signature="BaseQGT.run(circuits, parameter_values, parameters=None, **options)">
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Run the job of the QGTs on the given circuits.
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**Parameters**
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* **circuits** – The list of quantum circuits to compute the QGTs.
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* **parameter\_values** – The list of parameter values to be bound to the circuit.
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* **parameters** – The sequence of parameters to calculate only the QGTs of the specified parameters. Each sequence of parameters corresponds to a circuit in `circuits`. Defaults to None, which means that the QGTs of all parameters in each circuit are calculated.
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* **options** – Primitive backend runtime options used for circuit execution. The order of priority is: options in `run` method > QGT’s default options > primitive’s default setting. Higher priority setting overrides lower priority setting.
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**Returns**
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The job object of the QGTs of the expectation values. The i-th result corresponds to `circuits[i]` evaluated with parameters bound as `parameter_values[i]`.
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**Raises**
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**ValueError** – Invalid arguments are given.
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</Function>
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### update\_default\_options
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<Function id="qiskit.algorithms.gradients.BaseQGT.update_default_options" signature="BaseQGT.update_default_options(**options)">
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Update the gradient’s default options setting.
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**Parameters**
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**\*\*options** – The fields to update the default options.
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</Function>
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## Attributes
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### derivative\_type
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<Attribute id="qiskit.algorithms.gradients.BaseQGT.derivative_type">
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The derivative type.
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**Return type**
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[`DerivativeType`](qiskit.algorithms.gradients.DerivativeType "qiskit.algorithms.gradients.utils.DerivativeType")
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</Attribute>
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### options
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<Attribute id="qiskit.algorithms.gradients.BaseQGT.options">
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Return the union of estimator options setting and QGT default options, where, if the same field is set in both, the QGT’s default options override the primitive’s default setting.
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**Return type**
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[`Options`](qiskit.providers.Options "qiskit.providers.options.Options")
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**Returns**
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The QGT default + estimator options.
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</Attribute>
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</Class>
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