Realization of three- and four-body interactions between momentum states in a cavity.

Spin Hamiltonians in condensed matter and quantum sensing typically utilize pairwise or two-body interactions between constituents in the material or ensemble. However, there is growing interest in exploring more general n-body interactions for n > 2. In this study, we realized an effective n = 3-body Hamiltonian interaction using an ensemble of laser-cooled atoms in a high-finesse optical cavity with the pseudospin 1 / 2 encoded by two atomic momentum states. We applied two dressing tones that induce the atoms to exchange photons via the cavity to realize a virtual six-photon process; lower-order interactions destructively interfered. We also observed signatures of a n = 4-body interaction mediated by a virtual eight-photon process. Our approach may be extensible to three-body interactions in multilevel systems or to even higher-order interactions. Editor's summary: Interactions between pairs of particles often dominate over those in which three or more particles couple directly. To implement such higher-order interactions experimentally, pairwise interactions need to be suppressed. Luo et al. realized three- and four-body interactions between 1000 rubidium atoms held in an optical cavity. Lower-order two-body interactions were cancelled through symmetry. This technique may enable future explorations of exotic many-body physics as well as advances in quantum metrology. —Jelena Stajic [ABSTRACT FROM AUTHOR]