Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have used graphene and STM technology to create and image a novel pair of quantum dots — tiny islands of confined electric charge that act like interacting artificial atoms. Such “coupled” quantum dots could serve as a robust quantum bit, or qubit, the fundamental unit of information for a quantum computer. Moreover, the patterns of electric charge in the island can’t be fully explained by current models of quantum physics, offering an opportunity to investigate rich new physical phenomena in materials.
a system of coupled quantum dots taken by STM shows electrons orbiting within two concentric sets of rings, separated by a gap. The inner set of rings represents one quantum dot; the outer, brighter set represents a larger, outer quantum dot. Credit: NIST
The NIST -led team included researchers from the University of Maryland NanoCenter and the National Institute for Materials Science in Japan. The team used the ultrasharp tip of a scanning tunneling microscope (STM) as if it were a stylus of sorts. Hovering the tip above an ultracold sheet of graphene, the researchers briefly increased the voltage of the tip.