  The development and wide application of quantum technologies highly depend on
the capacity of the communication channels distributing entanglement.
Space-division multiplexing (SDM) enhanced channel capacities in classical
telecommunication and bears the potential to transfer the idea to quantum
communication using current infrastructure. Here, we demonstrate an SDM of
polarization-entangled photons over a 411m long 19-core multicore fiber
distributing polarization-entangled photon pairs through up to 12 channels
simultaneously. The quality of the multiplexed transfer is evidenced by high
polarization visibility and CHSH Bell inequality violation for each pair of
opposite cores. Our distribution scheme shows high stability over 24 hours
without any active polarization stabilization and can be effortlessly adapted
to a higher number of channels. This technique increases the quantum-channel
capacity and allows the reliable implementation of quantum networks of multiple
users based on a single entangled-photon pair source.
