  Trends in photonic quantum information follow closely the technical progress
in classical optics and telecommunications. In this regard, advances in
multiplexing optical communications channels have also been pursued for the
generation of multi-dimensional quantum states (qudits), since their use is
advantageous for several quantum information tasks. One current path leading in
this direction is through the use of space-division multiplexing multi-core
optical fibers, which provides a new platform for efficiently controlling
path-encoded qudit states. Here we report on a parametric down-conversion
source of entangled qudits that is fully based on (and therefore compatible
with) state-of-the-art multi-core fiber technology. The source design uses
modern multi-core fiber beam splitters to prepare the pump laser beam as well
as measure the generated entangled state, achieving high spectral brightness
while providing a stable architecture. In addition, it can be readily used with
any core geometry, which is crucial since widespread standards for multi-core
fibers in telecommunications have yet to be established. Our source represents
an important step towards the compatibility of quantum communications with the
next-generation optical networks.
