Mesoscopic Rydberg-blockaded ensembles in the superatom regime and beyond

To gain insight into the properties of quantum matter, a superatom—an ensemble of strongly interacting atoms in the Rydberg blockade regime—is created and characterized by precisely controlling the density and Rydberg excitations. The control of strongly interacting many-body systems enables the creation of tailored quantum matter with complex properties. Atomic ensembles that are optically driven to a Rydberg state provide many examples for this: atom–atom entanglement 1 , 2 , many-body Rabi oscillations 3 , strong photon–photon interaction 4 and spatial pair correlations 5 . In its most basic form Rydberg quantum matter consists of an isolated ensemble of strongly interacting atoms spatially confined to the blockade volume—a superatom. Here we demonstrate the controlled creation and characterization of an isolated mesoscopic superatom by means of accurate density engineering and excitation to Rydberg p -states. Its variable size allows the investigation of the transition from effective two-level physics to many-body phenomena. By monitoring continuous laser-induced ionization we observe a strongly anti-bunched ion emission under blockade conditions and extremely bunched ion emission under off-resonant excitation. Our measurements provide insights into both excitation statistics and dynamics. We anticipate applications in quantum optics and quantum information as well as many-body physics experiments.