  We study the problem of decoding classical information encoded on quantum
states at the output of a quantum channel, with particular focus on increasing
the communication rates towards the maximum allowed by Quantum Mechanics. After
a brief introduction to the main theoretical formalism employed in the rest of
the thesis, i.e., continuous-variable Quantum Information Theory and Quantum
Communication Theory, we consider several decoding schemes. First, we treat the
problem from an abstract perspective, presenting a method to decompose any
quantum measurement into a sequence of easier nested measurements through a
binary-tree search. Furthermore we show that this decomposition can be used to
build a capacity-achieving decoding protocol for classical communication on
quantum channels and to solve the optimal discrimination of some sets of
quantum states. These results clarify the structure of optimal quantum
measurements, showing that it can be recast in a more operational and
experimentally-oriented fashion. Second, we consider a more practical approach
and describe three receiver structures for coherent states of the
electromagnetic field with applications to single-mode state discrimination and
multi-mode decoding at the output of a quantum channel. We treat the problem
bearing in mind the technological limitations faced nowadays in the field of
optical communications: we evaluate the performance of general decoding schemes
based on such technology and report increased performance of two schemes, the
first one employing a non-Gaussian transformation and the second one employing
a code tailored to be read out easily by the most common detectors. Eventually
we characterize a large class of multi-mode adaptive receivers based on common
technological resources, obtaining a no-go theorem for their capacity.
