Number 88 (Story #1), July 13, 1992 by Phillip F. Schewe and Ben Stein THE MOVEMENT OF SINGLE ELECTRONS along a chain of defects in a semiconductor has been monitored by observing the conductance of a nearby channel; the channel is formed when a two-dimensional electron gas (electrons moving in a thin layer of GaAs sandwiched between layers of AlGaAs) is pinched down to a narrow strip by voltage applied to two gate electrodes. According to scientists at the Cavendish Laboratory in Cambridge, England, the tiny "hopping" current (amounting to a fraction of an attoamp, or 10**-18 amp) gives rise to a "random telegraph signal" in the conductance of the constriction, each level of which corresponds to a different configuration of electrons in the chain. The Cavendish workers expect that this technique can be used to follow single-electron processes in real time (and not just on a time-averaged basis) in other systems. (D.H. Cobden et al., 20 July 1992 issue of Physical Review Letters.)