In Schrödinger’s famous thought experiment, a cat seems to be both dead and alive-an idea that strains credulity. These days, cats still don’t act this way, but physicists now regularly create analogues of Schrödinger’s cat in the lab by smearing the microscopic quantum world over longer and longer distances. Such “cat states” have found many homes, promising more sensitive quantum measurements and acting as the basis for quantum error-correcting codes-a necessary component for future error-prone quantum computers.
National Institute of Standards and Technology (NIST) physicists have solved the seemingly intractablepuzzle of how to control the quantum properties of individual charged molecules, or molecular ions. Thesolution is to use the same kind of “quantum logic” that drives an experimental NIST atomic clock.