# qml.qinfo¶

## Overview¶

This module provides a collection of methods to return quantum information quantities from QNode returning state().

## Transforms¶

QNode transforms for the quantum information quantities.

### Functions¶

 classical_fisher(qnode[, argnums]) Returns a function that computes the classical fisher information matrix (CFIM) of a given QNode or quantum tape. fidelity(qnode0, qnode1, wires0, wires1) Compute the fidelity for two QNode returning a state() (a state can be a state vector or a density matrix, depending on the device) acting on quantum systems with the same size. mutual_info(qnode, wires0, wires1[, base]) Compute the mutual information from a QNode returning a state(): purity(qnode, wires) Compute the purity of a QNode returning state(). quantum_fisher(qnode, *args, **kwargs) Returns a function that computes the quantum fisher information matrix (QFIM) of a given QNode. reduced_dm(qnode, wires) Compute the reduced density matrix from a QNode returning state(). relative_entropy(qnode0, qnode1, wires0, wires1) Compute the relative entropy for two QNode returning a state() (a state can be a state vector or a density matrix, depending on the device) acting on quantum systems with the same size. vn_entropy(qnode, wires[, base]) Compute the Von Neumann entropy from a QNode returning a state().