Bringing Schrödinger's Cat to Life; June 1997; Scientific American Magazine; by Yam; 6 Page(s)

"I am sorry that I ever had anything to do with quantum theory," Erwin Schr¿dinger reportedly complained to a colleague. The Austrian physicist was not lamenting the fate of his now famous cat, which he figuratively placed in a box with a vial of poison in 1935. Rather he was commenting on the strange implications of quantum mechanics, the science behind electrons, atoms, photons and other things submicroscopic. With his feline, Schr¿dinger attempted to illustrate the problem: according to quantum mechanics, particles jump from point to point, occupy several places at once and seem to communicate faster than the speed of light. So why don¿t cats--or baseballs or planets or people, for that matter--do the same things? After all, they are made of atoms. Instead they obey the predictable, classical laws quantified by Isaac Newton. When does the quantum world give way to the physics of everyday life? "That¿s one of the $64,000 questions," chuckles David Pritchard of the Massachusetts Institute of Technology.

Pritchard and other experimentalists have begun to peek at the boundary between quantum and classical realms. By cooling particles with laser beams or by moving them through special cavities, physicists have in the past year created small-scale Schr¿dinger¿s cats. These "cats" were individual electrons and atoms made to reside in two places simultaneously, and electromagnetic fields excited to vibrate in two different ways at once. Not only do they show how readily the weird gives way to the familiar, but in dramatic fashion they illustrate a barrier to quantum computing--a technology, still largely speculative, that some researchers hope could solve problems that are now impossibly difficult.