One of the main initial challenges in theoretically understanding the emerging atom-nanophotonics interfaces is that many of the systems do not obviously fit into previously established models for quantum atom-light interactions. Within this context, we have developed a novel and universal formalism capable of describing atom-light interactions in complex dielectric settings. On one hand, this so-called quantum “spin model” has been crucial to understanding and modeling the first experiments in the world that observe atomic interactions in photonic crystal waveguides. On the other hand, it has been used to theoretically predict new and exotic phenomena that should be realizable with such systems, such as the formation of molecules of photons, or “quantum crystallization,” in which entanglement between atomic internal degrees of freedom are responsible for the formation and stabilization of spatial order. We have also used this model to develop powerful new numerical techniques, in combination with tensor network methods, to remove exponential inefficiencies from previous techniques to calculate the full quantum dynamics in the interaction between propagating light fields and atomic media.
Furthermore, due to its universal nature, the spin model can even be used to provide new insights into “conventional” atomic systems, such as free-space ensembles. One interesting aspect of this model is that it accounts for multiple scattering and interference of light emission, which are not included in conventional models. We have shown that interference can be a remarkable resource. For example, by exploiting interference, we have developed a new protocol for a quantum memory for light, whose error bound as a function of system resources is exponentially better than previously developed bounds. We have also shown that this model may provide insights on why the refractive index of materials at optical frequencies is universally so small, being always of order unity.
FOQAL has resulted in at least 27 publications in total, including in prominent journals such as PRX (3 publications), Nature Communications (2), Nature, and a review of the new field of atom-nanophotonics interfaces in Review of Modern Physics. These include two collaborative papers with experiments that explore the phenomena that we have proposed. Furthermore, we have reached an audience of over 5000 researchers, through dissemination in workshops, conferences, seminars, and schools.
