Microscopy of Ultracold Polar Molecules in Optical Lattices

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The world of microscopic particles like atoms or molecules is governed by the laws of quantum mechanics. While these laws describe phenomena unfamiliar in our daily experience, they can be used to engineer revolutionary technologies. Examples include very precise clocks or powerful computers that can solve intractable problems in diverse fields ranging from drug discovery to artificial intelligence. A key requirement for harnessing the power of quantum mechanics for many applications is gaining microscopic control over large systems of interacting quantum particles. This award supports the development of an instrument, a "molecular quantum gas microscope" that will achieve this level of control in a gas of thousands of molecules. Even the very simple molecules used in this experiment exhibit rich behaviors compared to atoms. For example, molecules tumble in space, and the constituent atoms vibrate relative to each other. In addition, molecules made of different atoms are "polar," behaving much like fridge magnets that interact strongly even at a large distance. By cooling molecular gases down to very low temperatures, the quantum nature of their motions and their strong mutual interactions play an increasingly important role and lead to the rearrangement of the molecules into unusual states of matter. These states will be directly imaged and controlled at the level of individual molecules using the molecular microscope. The project will further our understanding of interacting quantum matter, with a potential impact on designing materials with new technological properties. It also holds the potential for realizing a molecule-based platform for quantum computing. The research will train graduate students in the burgeoning field of quantum science, preparing them for future careers in academia, industry and national labs. Ultracold gases of polar molecules are promising for many applications including quantum computation, precision measurements and studies of state-controlled chemical reactions. One application that has been the subject of much recent attention is the quantum simulation of many-body phenomena. The long-range and anisotropic character of the interactions between polar molecules enables quantum simulations that address a variety of areas of contemporary interest in condensed matter physics including out-of-equilibrium quantum dynamics, topological matter and quantum magnetism. An outstanding challenge in this emerging field is the ability to measure and manipulate the quantum state of individual molecules in an interacting array. This project will develop microscopy techniques that enable the extraction of the positions of individual ground-state molecules in an optical lattice with single-site accuracy and the determination of their rotational state. To that end, molecules will be dissociated in a state-sensitive way into their constituent atoms, which will be subsequently detected using well-developed atomic quantum gas microscopy techniques. The project will also study the evaporation of the bosonic molecules to quantum degeneracy, using a large electric field to suppress inelastic collisions. The strong dipolar interactions in a degenerate molecular Bose gas are expected to lead to novel phases of matter, including self-organized crystals and fractional Mott insulators. The molecular quantum gas microscope will enable direct imaging and control of these phases and their excitations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.