  We present a method to detect properties of quantum channels, assuming that
some a priori information about the form of the channel is available. The
method is based on a correspondence with entanglement detection methods for
multipartite density matrices based on witness operators. We first illustrate
the method in the case of entanglement breaking channels and non separable
random unitary channels, and show how it can be implemented experimentally by
means of local measurements. We then study the detection of non separable maps
and show that for pairs of systems of dimension higher than two the detection
operators are not the same as in the random unitary case, highlighting a richer
separability structure of quantum channels with respect to quantum states.
Finally we consider the set of PPT maps, developing a technique to reveal NPT
maps.
