Individual photons can be used to quantum mechanically couple waveguides together as a means to store information and perform calculations. The technique could potentially lead to the production of quantum computers that will be able to solve problems that are far beyond the capability of any conventional computer.
This image shows how light injected into a central waveguide couples together a collection of neighboring waveguides.
This research was performed by Amit Rai, G. S. Agarwal, and J. H. H. Perk, Department of Physics, Oklahoma State University, and was published in Physical Review A (Atomic, Molecular, and Optical Physics), October 8, 2008.
"Transport and quantum walk of nonclassical light in coupled waveguides," Phys. Rev. A 78, 042304 (2008)