This image shows the coherent flow of electrons through a quantum point contact formed in a two dimensional electron gas inside a GaAs/AlGaAs heterostructure. Scanned probe microscope images on the outside agree well with theoretical simulations inside. The fringes are spaced by half the electron wavelength.

Robert Westervelt and Eric Heller at Harvard University, Arthur C. Gossard at UC Santa Barbara, Physics Today 56(12) (2003).

Image courtesy: Dr. Eric Heller, Harvard University.