  With increasing commercial availability of quantum information processing
devices the need for testing them efficiently for their specified functionality
will arise. Complete quantum channel characterization is out of the question
for anything more than the simplest quantum channels for one or two qubits.
Quantum functional testing leads to a decision problem with outcomes
corresponding to rejection or acceptance of the claim of the producer that the
device parameters are within certain specifications. In this context, we
introduce and analyse three ingredients that can speed up this decision
problem: iteration of the channel, efficient decision criteria, and non-greedy
adaptive experimental design.
