From CIQC PI David Weld’s research group:
By throwing atoms and watching them come back to the starting point, experimentalists have now observed for the first time a dynamical feature of disordered quantum matter called the “quantum boomerang effect.” More than 60 years ago Phil Anderson pointed out that quantum mechanical effects of disorder in a material can localize electrons– that is, prevent them from leaving a small neighborhood, thereby turning a metal into an insulator. Only recently, theorists predicted that if a particle is launched in any direction in an Anderson insulator, it will return to its point of origin and remain there, rather than gradually coming to a halt nearby as one would classically expect. This fundamentally quantum-mechanical phenomenon has now been observed experimentally in a kicked quantum gas by Sajjad and collaborators. The authors not only observe the characteristic return of the boomerang, but also demonstrate that the quantum boomerang effect can be controllably switched on and off by adjusting symmetries of the initial state or adding temporal disorder. These results showcase a unique experimental probe of the underlying quantum nature of disordered matter.