QFIBase¶

class QFIBase(qfi_method='lin_comb_full')[source]¶

Bases: DerivativeBase

Deprecated: Base class for Quantum Fisher Information (QFI).

Compute the Quantum Fisher Information (QFI) given a pure, parameterized quantum state.

The QFI is:

[QFI]kl= Re[〈∂kψ|∂lψ〉−〈∂kψ|ψ〉〈ψ|∂lψ〉] * 4.

Deprecated since version 0.24.0: The class qiskit.opflow.gradients.qfi_base.QFIBase 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.

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.

Attributes

qfi_method¶

Returns CircuitQFI.

Returns: CircuitQFI.