  Dense photonic integration promises to revolutionize optical computing and
communications. However, efforts towards this goal face unacceptable
attenuation of light caused by surface roughness in microscopic devices. Here
we address this problem by introducing Surface Nanoscale Axial Photonics
(SNAP). The SNAP platform is based on whispering gallery modes circulating
around the optical fiber surface and undergoing slow axial propagation readily
described by the one-dimensional Schr\"odinger equation. These modes can be
steered with dramatically small nanoscale variation of the fiber radius, which
is quite simple to introduce in practice. The extremely low loss of SNAP
devices is achieved due to the fantastically low surface roughness inherent in
a drawn fiber surface. In excellent agreement with the developed theory, we
experimentally demonstrate localization of light in quantum wells, halting
light by a point source, tunneling through potential barriers, dark states,
etc. This demonstration, prototyping basic quantum mechanical phenomena with
light, has intriguing potential applications in filtering, switching, slowing
light, and sensing.
