QFI#

class 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.