  We investigate an array of metal nanoparticles as a channel for nanophotonic
quantum communication and the generation of quantum plasmonic interference. We
consider the transfer of quantum states, including single-qubits as plasmonic
wavepackets, and highlight the necessity of a quantum mechanical description by
comparing the predictions of quantum theory with those of classical
electromagnetic theory. The effects of loss in the metal are included, thus
putting our investigation into a practical setting and enabling the
quantification of the performance of realistic nanoparticle arrays as plasmonic
quantum channels. We explore the interference of single plasmons, finding
nonlinear absorption effects associated with the quantum properties of the
plasmon excitations. This work highlights the benefits and drawbacks of using
nanophotonic periodic systems for quantum plasmonic applications, such as
quantum communication, and the generation of quantum interference.
