QFI
class QFI(qfi_method='lin_comb_full')
Bases: qiskit.opflow.gradients.qfi_base.QFIBase
Compute the Quantum Fisher Information (QFI).
Computes the QFI given a pure, parameterized quantum state, where QFI is:
Parameters
qfi_method (Union[str, CircuitQFI]) – The method used to compute the state/probability gradient. Can be either a CircuitQFI instance or one of the following pre-defined strings 'lin_comb_full', 'overlap_diag'` or 'overlap_block_diag'`.
Raises
ValueError – if qfi_method is neither a CircuitQFI object nor one of the predefined strings.
Methods Defined Here
convert
QFI.convert(operator, params=None)
Parameters
- operator (
CircuitStateFn) – The operator corresponding to the quantum state |ψ(ω)〉for which we compute the QFI - params (
Union[ParameterVector,ParameterExpression,List[ParameterExpression],None]) – The parameters we are computing the QFI wrt: ω If not explicitly passed, they are inferred from the operator and sorted by name.
Return type
ListOp
Returns
ListOp[ListOp] where the operator at position k,l corresponds to QFI_kl
Raises
ValueError – If operator is not parameterized.
Attributes
qfi_method
Returns CircuitQFI.
Return type
CircuitQFI
Returns
CircuitQFI.