Nature Phys. doi:10.1038/nphys1278, (2009)

In the whacky world of quantum mechanics, particles can act as waves and waves as particles. Physicists wondered whether this duality might also be true for a form of collective motion known as a 'surface plasmon polariton', which arises when light excites electrons on a metallic surface.

Among other quantum properties, plasmon polaritons seem to have wave–particle behaviour. Fedor Jelezko and Jörg Wrachtrup at the University of Stuttgart in Germany and their colleagues looked at plasma polaritons on the surface of a silver nanowire and found that they interfered with themselves — a telltale signature of wave–particle duality. The authors say the work will prove useful, particularly in the development of quantum networks.