A New Spin on Quantum Atom-Light Interactions

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A central goal of quantum optics is to realize efficient, controlled quantum interfaces between atoms and photons. Such interfaces enable broad applications from quantum information processing to quantum nonlinear optics to metrology, and also open a route toward creating exotic quantum states of light and matter. Today, our major paradigm for realizing an efficient interface is based upon the concept of collective enhancement, where using a large number of atoms creates an enhanced coupling to a preferred optical mode over undesired emission into other directions. However, our known error bounds for applications decrease very slowly as a function of system resources, such as the optical depth, thus posing a great challenge for future technologies. In NEWSPIN, we propose a remarkable new way forward, based upon the realization that these conventional error bounds are derived without accounting for multiple scattering and wave interference between emitting atoms. We aim to establish that interference in light emission is in fact a much more powerful resource than the level that we currently exploit it. In particular, beyond the usual collective enhancement, it can simultaneously enable a much stronger collective suppression of emission into undesired directions, and which can yield exponentially better error bounds than was previously known. Underlying this powerful paradigm shift will be the development of a quantum many-body theory of multiple scattering involving photons and atoms, which takes advantage of state-of-the-art tools from condensed matter physics. Beyond robust new routes toward applications, our theory will also reveal exotic new quantum phenomena and lead to new insights into fundamental questions in optics, such as the physical limits to how large the refractive index of an optical material can be. In total, we anticipate that NEWSPIN could greatly enrich our understanding of atom-light interactions and their realm of possibilities.