Dec 4, 2024: Darrick Chang [ICFO]

Title: Quantum optics with atom arrays: from efficient photon gates to quantum spin liquids
Abstract: Most synthetic quantum platforms today feature highly coherent, short-range interactions between their individual elements. In contrast, quantum atom-light interfaces are markedly different. First, light naturally facilitates long-range interactions between atoms, which often results in simple, mean-field behavior. Second, and more importantly, high-fidelity operations between atoms and photons remains an outstanding challenge. Physically, the emission of photons by excited atoms into directions that cannot be efficiently collected constitutes a major loss of quantum information in many applications. For example, state-of-the-art photon entangling gates still exhibit an error probability of over 50%.
In recent years, an exciting new paradigm has emerged to harness this dissipation. In particular, it has been realized that spontaneous emission is actually a form of correlated dissipation, due to the interference of light emitted by different atoms. The correlated nature becomes especially strong and controllable in dense atom arrays. Here, we discuss our recent theoretical efforts to efficiently encode applications and interesting many-body phenomena into atom-light interfaces, utilizing the collective dissipation and long-range interactions while avoiding mean-field behavior. Starting at the single-photon level, we show how to realize quantum memories and photon gates with errors that are exponentially smaller versus atom number than previously known protocols. We then discuss paradigms in which long-range interactions can facilitate the formation of topological quantum spin liquids, exotic states of matter whose low-energy physics are described by emergent gauge fields and fractional excitations.