  We report an experimental realisation of a quantum random number generator
using a plasmonic beamsplitter. Free-space single photons are converted into
propagating single surface plasmon polaritons on a gold stripe waveguide via a
grating. The surface plasmons are then guided to a region where they are
scattered into one of two possible outputs. The presence of a plasmonic
excitation in a given output determines the value of a random bit generated
from the quantum scattering process. Using a stream of single surface plasmons
injected into the beamsplitter we achieve a quantum random number generation
rate of 2.37 Mbits/s even in the presence of loss. We characterise the quality
of the random number sequence generated, finding it to be comparable to
sequences from other quantum photonic-based devices. The compact nature of our
nanophotonic device makes it suitable for tight integration in on-chip
applications, such as in quantum computing and communication schemes.
