---
title: QFI (v0.46)
description: API reference for qiskit.algorithms.gradients.QFI in qiskit v0.46
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/0.46/qiskit.algorithms.gradients.QFI
---

# QFI

*class* `qiskit.algorithms.gradients.QFI(qgt, options=None)`

[GitHub](https://github.com/qiskit/qiskit/tree/stable/0.46/qiskit/algorithms/gradients/qfi.py)

Bases: [`ABC`](https://docs.python.org/3/library/abc.html#abc.ABC)

Computes the Quantum Fisher Information (QFI) given a pure, parameterized quantum state. QFI is defined as:

$$
\mathrm{QFI}_{ij}= 4 \mathrm{Re}[\langle \partial_i \psi | \partial_j \psi \rangle
- \langle\partial_i \psi | \psi \rangle \langle\psi | \partial_j \psi \rangle].
$$

**Parameters**

- **qgt** ([*BaseQGT*](/docs/api/qiskit/0.46/qiskit.algorithms.gradients.BaseQGT "qiskit.algorithms.gradients.BaseQGT")) – The quantum geometric tensor used to compute the QFI.
- **options** ([*Options*](/docs/api/qiskit/0.46/qiskit.providers.Options "qiskit.providers.Options") *| None*) – Backend runtime options used for circuit execution. The order of priority is: options in `run` method > QFI’s default options > primitive’s default setting. Higher priority setting overrides lower priority setting.

## Attributes

### options

Return the union of QGT’s options setting and QFI’s default options, where, if the same field is set in both, the QFI’s default options override the QGT’s default setting.

**Returns**

The QFI default + QGT options.

## Methods

### run

`run(circuits, parameter_values, parameters=None, **options)`

Run the job of the QFIs on the given circuits.

**Parameters**

- **circuits** (*Sequence\[*[*QuantumCircuit*](/docs/api/qiskit/0.46/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")*]*) – The list of quantum circuits to compute the QFIs.
- **parameter\_values** (*Sequence\[Sequence\[*[*float*](https://docs.python.org/3/library/functions.html#float)*]]*) – The list of parameter values to be bound to the circuit.
- **parameters** (*Sequence\[Sequence\[*[*Parameter*](/docs/api/qiskit/0.46/qiskit.circuit.Parameter "qiskit.circuit.Parameter")*] | None] | None*) – The sequence of parameters to calculate only the QFIs of the specified parameters. Each sequence of parameters corresponds to a circuit in `circuits`. Defaults to None, which means that the QFIs of all parameters in each circuit are calculated.
- **options** – Primitive backend runtime options used for circuit execution. The order of priority is: options in `run` method > QFI’s default options > QGT’s default setting. Higher priority setting overrides lower priority setting.

**Returns**

The job object of the QFIs of the expectation values. The i-th result corresponds to `circuits[i]` evaluated with parameters bound as `parameter_values[i]`.

**Return type**

[AlgorithmJob](/docs/api/qiskit/0.46/qiskit.algorithms.AlgorithmJob "qiskit.algorithms.AlgorithmJob")

### update\_default\_options

`update_default_options(**options)`

Update the gradient’s default options setting.

**Parameters**

**\*\*options** – The fields to update the default options.