  Relativistic massless charged particles in a two-dimensional conductor can be
guided by a one-dimensional electrostatic potential, in an analogous manner to
light guided by an optical fiber. We use a carbon nanotube to generate such a
guiding potential in graphene and create a single mode electronic waveguide.
The nanotube and graphene are separated by a few nanometers and can be
controlled and measured independently. As we charge the nanotube, we observe
the formation of a single guided mode in graphene that we detect using the same
nanotube as a probe. This single electronic guided mode in graphene is
sufficiently isolated from other electronic states of linear Dirac spectrum
continuum, allowing the transmission of information with minimal distortion.
