Quantum materials and quantum sensors with atomic and molecular gases

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Quantum mechanics is the universal mathematical language that we use to describe and predict the behavior of physical systems. While encompassing standard or so-called "classical" properties, the predictions of quantum mechanics also include exotic and surprising phenomena that are both challenging our ideas about the nature of reality and being exploited to improve society through better communication (quantum cryptography), data storage (quantum effects in solid state devices), inertial navigation (atom interferometers), and measurement technologies (quantum sensors). The aim of this research program is to use laser-cooled gases to explore fundamental questions in many-body quantum phenomena and to use these gases to realize new quantum sensors with industrial and commercial relevance. Technological breakthroughs in laser-cooling of atoms and molecules have created a new realm of ultra-low temperature science. At temperatures very near absolute zero (in the micro- to nano-kelvin range), these ultra-cold quantum materials offer us access to completely novel sensing elements and novel states of matter inaccessible by any other means. The unique detection methods and the degree of control available in these systems (including the ability to dynamically tune the particle-particle interactions, the particle density, and the confinement geometry), provide direct experimental access to some of the most important and fundamental phenomena of few and many-body quantum mechanics. Consider for example, the question "What are the collective behaviors of a system of strongly interacting quantum particles?" This question is central to understanding an array of physical systems of both fundamental and technological interest from the microscopic to the astronomical scale including quark-gluon plasmas, electrons in high-Tc superconductors, super-fluid liquid helium, ultra-cold atomic gases, and nucleons in neutron stars. Indeed, every physical object that exists, except for an elementary particle, is a many-body quantum system, and at present, theoretical understanding of strongly interacting many-body systems is still limited because interactions can make the particle-particle correlations dominate the behavior and then mean-field theory and perturbative analysis are inadequate. In order to advance fundamental knowledge and technology, it is essential to establish the validity of new theoretical approaches by comparing them with clean and reproducible experimental measurements. Ultra-cold atomic or molecular gases have already demonstrated that they are an ideal experimental testbed for this purpose because of the aforementioned degree of control, their reproducibility, and the wide array of measurement options they yield. In addition studying quantum materials, we aim to create new sensors where the sensor element itself is a quantum of matter (e.g. a single atom or a single molecule). Cold atoms have already been used to realize the most accurate and sensitive gravitational and inertial sensors with matter wave interferometry and to realize our primary frequency/time standard (an atomic fountain clock). We will begin with the development of a new sensor technology we recently demonstrated - the use of cold atoms to measure particle flux in an ultra-high vacuum. This technology is expected to impact, among other things, semi-conducting fabrication processes which rely on controlling particle densities and fluxes in vacuum. In these ways, research on cold atomic and molecular gases is advancing both fundamental and applied science providing answers to basic questions about the nature of matter and providing tangible and immediate benefits to our way of life by improved communication, fabrication, and sensing technologies.