QFI

class qiskit.algorithms.gradients.QFI(qgt, options=None)[source]

Bases: 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) – The quantum geometric tensor used to compute the QFI.

  • options (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(circuits, parameter_values, parameters=None, **options)[source]

Run the job of the QFIs on the given circuits.

Parameters:

  • circuits (Sequence[QuantumCircuit]) – The list of quantum circuits to compute the QFIs.

  • parameter_values (Sequence[Sequence[float]]) – The list of parameter values to be bound to the circuit.

  • parameters (Sequence[Sequence[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

update_default_options(**options)[source]

Update the gradient’s default options setting.

Parameters:

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