VIEWPOINT Atoms Oscillate Collectively in Large

O ptical lattices are key elements in the effort to use ultracold atoms for quantum simulation, quantum computing, and atomic clocks. These lattices rely on light forces to precisely hold atoms in space and to individually control their internal states [1]. Researchers strive for nearly perfect periodic lattice structures using state-of-the-art laser systems, but the atoms can interfere with these efforts by scattering photons that perturb the light fields that form the lattice. Normally, this backaction is kept at a minimum, but researchers have realized they can harness the atoms’ influence on the lattice for something useful: to generate interactions between atoms. To explore this possibility, Philipp Treutlein from the University of Basel in Switzerland and colleagues have built a hybrid system composed of a one-dimensional optical lattice coupled to vibrations of a mobile membrane inside an optical resonator [2]. The combination of membrane and resonator amplifies the collective motions of the atoms, producing an instability in the membrane vibrations. This instability, which would be undesirable in most situations, is evidence of longrange (phonon-like) interactions between the atoms. Such interactions could be implemented in cold-atom quantum simulations, where they would mimic the phonon dynamics of “real” lattices inside solids.