  The aim of this work is to answer the question of how much quantum coherence
a beam splitter is able to produce. To this end we consider as the variables
under study both the amount of coherence of the input states as well as the
beam splitter characteristics. We conclude that there is an optimal combination
of these factors making the gain of coherence maximum. In addition, the two
mode squeezed vacuum arises as the studied state most capable of gaining
coherence when passing through a beam splitter. These results are qualitatively
equivalent for the the l1-norm of coherence and for the relative entropy of
coherence.
