QUANTUM COOL Physicists at Simon Fraser University in Vancouver are trying to get electrical circuits to cool themselves electrostatically. To do this they employ both quantum and classical physics. First, the classical: a gas can cool down by pushing against a piston; some of the gas's thermal energy is converted into mechanical energy. Second, the quantum: electrons flowing from one GaAs layer into another via another a thin layer of AlGaAs will move with optimum efficiency if the electron energy matches a preferred "resonant" energy in the AlGaAs layer. This three-layer setup, called a quantum well, is at the heart of grocery-store laser scanners and CD players. As circuitry shrinks, disposing of waste heat from even tiny electric currents becomes an ever greater problem. The Simon Fraser researchers are proposing that the electrons in a quantum well cool themselves by moving against not a piston but against an opposing electric field, a field in addition to the one moving the electrons through their circuit. This way of combining the quantum (the electrons as waves tunneling through a thin layer) and the classical (the electrons as a working fluid in a sort of Carnot heat engine) might lead to a completely new category of microelectronic quantum device. (Luis Rego and George Kirczenow, kirczenow@sfu.edu, Applied Physics Letters, tent. 11 Oct.)