Cost Functions
==============

A cost function quantifies the performance of the quantum network at a particular task.
A cost function is evaluated for a given network ansatz and settings.
In general, a quantum network cost function requires one or more executions of a PennyLane
QNode.

For convenience, we provide example cost functions for quantum networks.
Custom cost functions can be implemented using PennyLane.

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.. toctree::
   :maxdepth: 1
   :caption: Contents:

   qnodes
   linear_inequalities
   entropic_quantities
   magic_squares_game
   nonlocality_witnesses/index