  A far-reaching goal of graphene research is exploiting the unique properties
of carriers to realize extreme nonclassical electronic transport. Of particular
interest is harnessing wavelike carriers to guide and direct them on submicron
scales, similar to light in optical fibers. Such modes, while long anticipated,
have never been demonstrated experimentally. In order to explore this behavior,
we employ superconducting interferometry in a graphene Josephson junction to
reconstruct the real-space supercurrent density using Fourier methods. Our
measurements reveal charge flow guided along crystal boundaries close to charge
neutrality. We interpret the observed edge currents in terms of guided-wave
states, confined to the edge by band bending and transmitted as plane waves. As
a direct analog of refraction-based confinement of light in optical fibers,
such nonclassical states afford new means for information transduction and
processing at the nanoscale.
