Session M02: Many-body Physics with Collective Atom-light Interactions

Universality of Dicke superradiance in atomic arrays

Tightly packed ordered arrays of atoms exhibit remarkable collective optical properties, as dissipation in the form of photon emission is correlated. In this talk, I will discuss the many-body out-of-equilibrium physics of atomic arrays, and focus on the problem of Dicke superradiance, where a collection of excited atoms synchronizes as they decay, emitting a short and intense pulse of light. Superradiance remains an open problem in extended systems due to the exponential growth of complexity with atom number. I will show that superradiance is a universal phenomenon in ordered arrays, and generically occurs if the inter-atomic distance is small enough. Our predictions can be tested in state of the art experiments with arrays of neutral atoms, molecules, and solid-state emitters and pave the way towards understanding the role of many-body decay in quantum simulation, metrology, and lasing.   

A Single Rydberg Atom Controlled Optical Mirror formed by Subwavelength Arrays of Atoms

Efficient and versatile interfaces for the interaction of light with matter are an essential cornerstone for quantum science. A fundamentally new avenue of controlling light-matter interactions has been recently proposed based on the rich interplay of photon-mediated dipole-dipole interactions in structured subwavelength arrays of quantum emitters. Here we report on the direct observation of the cooperative subradiant response of a two-dimensional (2d) square array of atoms in an optical lattice. We observe a spectral narrowing of the collective atomic response well below the quantum-limited decay of individual atoms into free space. Through spatially resolved spectroscopic measurements, we show that the array acts as an efficient mirror formed by only a single monolayer of a few hundred atoms.   We also show how the optical properties of the entire array can be switched via a single Rydberg impurity that is deterministically prepared in the center of the array. This opens the path towards novel structured quantum light matter interfaces with unique properties as well as the path towards entanglement generation between light and matter.   

An Optical Lattice with Sound

Quantized sound waves---phonons---govern the elastic response of crystalline materials, and also play an integral part in determining their thermodynamic properties and electrical response (e.g., by binding electrons into superconducting Cooper pairs). The physics of lattice phonons and elasticity is absent in simulators of quantum solids constructed of neutral atoms in periodic light potentials:  unlike real solids, traditional optical lattices are silent because they are infinitely stiff.  Optical-lattice realizations of crystals therefore lack some of the central dynamical degrees of freedom that determine the low-temperature properties of real materials. We will discuss our creation of an optical lattice with phonon modes using a Bose-Einstein condensate (BEC) coupled to a confocal optical resonator.  Playing the role of an active quantum gas microscope, the multimode cavity QED system both images the phonons and induces the crystallization that supports phonons via short-range, photon-mediated atom-atom interactions. Our results pave the way for exploring the rich physics of elasticity in quantum solids.   

Optical manipulation of many-body systems of planar arrays of atoms

Resonant light can couple strongly to subwavelength-spaced planar arrays of atoms where multiple scattering mediates long-range interactions and cooperative atom response. The cooperative response can be harnessed for engineering collective radiative excitations that correspond to those formed by arrays of magnetic dipoles and other multipoles, even when the atoms only exhibit electric dipole transitions [1]. Such optically active magnetism in neutral atomic system can be utilized in optical manipulation reminiscent of that considered in artificially fabricated metasurfaces. In particular, the atoms can form a Huygens’ surface, a physical realization of the Huygens’ principle, that provides an extreme wavefront control of transmitted light [1]. We compare the response of atom arrays to that of cavity qed and also show how the cooperative many-body response can be described by notably simpler superatom models that accurately predict reflection, transmission, photon storage, and non-classical resonance fluorescence [2-4].