  Quantum hypothesis testing has been greatly advanced for the binary
discrimination of two states, or two channels. In this setting, we already know
that quantum entanglement can be used to enhance the discrimination of two
bosonic channels. Here, we remove the restriction of binary hypotheses and show
that entangled photons can remarkably boost the discrimination of multiple
bosonic channels. More precisely, we formulate a general problem of
channel-position finding where the goal is to determine the position of a
target channel among many background channels. We prove that, using entangled
photons at the input and a generalized form of conditional nulling receiver at
the output, we may outperform any classical strategy. Our results can be
applied to enhance a range of technological tasks, including the optical
readout of sparse classical data, the spectroscopic analysis of a frequency
spectrum, and the determination of the direction of a target at fixed range.
