The field of Quantum Optics investigates the interaction between light and matter at the fundamental level. There, emitters (typically atoms) absorb and emit light (photons), giving rise to many phenomena that we observe in our lives. Furthermore, this simple process is at the basis of many devices, ranging from lasers to the most sophisticated medical tools. It also plays a crucial role in the development of new applications, like quantum computers, quantum communication devices, or quantum sensors.
In very recent years, technological advances have allowed us to trespass microscopic frontiers and enter a new dimension in the interaction of light and matter. Now it is possible to put atoms close to some dieletric materials (isolators), where they behave in a completely different way to what it has been observed so far. In particular, if one is able to write some microscopic structures on that material (yielding, what is called, a photonic crystal) atoms absorb and emit photons in a very different way as in free space. For instance, one atom (emitter) can emit and reabsorb a photon many times before it finally reaches out, or several of them can interchange one photon, giving rise to effective atom-atom interactions. One speaks of a “structured” bath for the emitter, in the sense that the density of states, that defines how photons move in the photonic crystal, has unconventional properties. In fact, we know neither what new phenomena can occur in this situation, nor how to describe them theoretically.
The problem addressed in QUENCOBA is precisely to investigate this QUantum Emitters in NOn-COnventinal BAths and to extend the theory of Quantum Optics to this new and complex scenario. It also aimed at developing the theoretical and computational tools to address the difficult problems that arise in the description of those experiments, as well as to harness those new phenomena to build better quantum devices. Although this project dealt with basic science, as it aimed at understanding fundamental processes that occur under special situations, it also developed the theoretical and computational techniques that are required to build such devices.
The overall objectives of the project were: (i) to develop the theoretical tools required to investigate this new area of research; (ii) to explore and characterize novel phenomena and to develop the analytical and computational techniques required for that; and (iii) propose and analyze other physical setups where those phenomena can be observed and exploited (in the context of quantum information and simulation). The research involveed the development of innovative techniques to describe new scenarios in quantum optics and many-body physics, as well as research on atoms interacting with photonic crystals, in optical lattices, and quantum dots interacting with surface acoustic waves.
In conclusion, we have investigated how atoms interacting with engineered baths give rise to novel phenomena, like the absence of emission of photons or the emission in very peculiar patterns. These phenomena can be observed experimentally, and could be harnessed in different ways, for instance to obtain better quantum photon emitters, or to address difficult problems in chemistry. Along the way, we have introduced new methodologies to deal with complex situations and developed a variety of computational methods that may be used in other contexts, like condensed matter or high energy physics.
