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The World's Smallest Abacus?
a small abacus made of moleculesDeveloped in ancient times, the abacus is an instrument used to make simple arithmetic calculations. Still in use in some parts of the world, the abacus consists of a wooden frame with beads on parallel wires or rods, and a perpendicular crossbar dividing the beads into two groups. This abacus, made by the folks at IBM's Research Division Zurich laboratory, consists of stable rows of ten molecules arranged along steps just one atom high. These steps act like rails, keeping the molecules in line much like the grooves one would find on the earliest type of abacus which had grooves instead of wires or rods. The "finger" required to manipulate this abacus is the ultrafine needle of a scanning tunneling microscope, conical in shape and terminating in a single atom at the tip. The microscope, in imaging mode, is also what makes the results of the molecular calculation visible through pictures like this one.

       
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Photo credit: Copyright © IBM.