# CircuitQFI

`qiskit.opflow.gradients.CircuitQFI`

Bases: `ConverterBase`

Deprecated: Circuit to Quantum Fisher Information operator converter.

Converter for changing parameterized circuits into operators whose evaluation yields Quantum Fisher Information metric tensor with respect to the given circuit parameters

This is distinct from DerivativeBase converters which take gradients of composite operators and handle things like differentiating combo_fn’s and enforcing product rules when operator coefficients are parameterized.

CircuitQFI - uses quantum techniques to get the QFI of circuits DerivativeBase - uses classical techniques to differentiate opflow data structures

The class `qiskit.opflow.gradients.circuit_qfis.circuit_qfi.CircuitQFI`

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 (opens in a new tab).

## Methods

### convert

`abstract convert(operator, params)`

**Parameters**

**operator**(*OperatorBase*) – The operator corresponding to the quantum state $|\psi(\omega)\rangle$ for which we compute the QFI.**params**(*ParameterExpression**|**ParameterVector**|**List*(opens in a new tab)*[**ParameterExpression**]*) – The parameters $\omega$ with respect to which we are computing the QFI.

**Returns**

An operator whose evaluation yields the QFI metric tensor.

**Raises**

**ValueError** (opens in a new tab) – If `params`

contains a parameter not present in `operator`

.

**Return type**