qiskit.opflow.gradients.CircuitQFI

class CircuitQFI

Circuit to Quantum Fisher Information operator converter.

Converter for changing parameterized circuits into operators whose evaluation yields Quantum Fisher Information metric tensor with respect to the given circuit parameters

This is distinct from DerivativeBase converters which take gradients of composite operators and handle things like differentiating combo_fn’s and enforcing product rules when operator coefficients are parameterized.

CircuitQFI - uses quantum techniques to get the QFI of circuits DerivativeBase - uses classical techniques to differentiate opflow data structures

__init__()

Initialize self. See help(type(self)) for accurate signature.

Methods

__init__()	Initialize self.
convert(operator, params)	type operator OperatorBase

abstract convert(operator, params)

Parameters

• operator (OperatorBase) – The operator corresponding to the quantum state \(|\psi(\omega)\rangle\) for which we compute the QFI.

• params (Union[ParameterExpression, ParameterVector, List[ParameterExpression]]) – The parameters \(\omega\) with respect to which we are computing the QFI.

Return type

OperatorBase

Returns

An operator whose evaluation yields the QFI metric tensor.

Raises

ValueError – If params contains a parameter not present in operator.