QFIBase
class qiskit.opflow.gradients.QFIBase(qfi_method='lin_comb_full')
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.
The class qiskit.opflow.gradients.qfi_base.QFIBase is deprecated as of qiskit-terra 0.24.0. It will be removed in the Qiskit 1.0 release. For code migration guidelines, visit https://qisk.it/opflow_migration(opens in a new tab).
Parameters
qfi_method (str(opens in a new tab) |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(opens in a new tab) – if qfi_method is neither a CircuitQFI object nor one of the predefined strings.
Attributes
qfi_method
Returns CircuitQFI.
Returns
CircuitQFI.