Community Research and Development Information Service - CORDIS


Techniques to interface atomic systems with quantum optical fields are expected to form a cornerstone for future technologies that aim to exploit the laws of quantum physics for enhanced performance over classical devices. Promising applications include quantum information processing, nonlinear optics at the level of single photons, and the simulation of strongly correlated quantum systems. The promise of quantum interfaces between cold atoms and light stems from the demonstrated ability to use atoms to generate and process quantum information in the form of photons, and the nature of light as a preferred carrier of information over long distances. The vast majority of interfaces developed thus far have been in relatively bulky geometries, such as atomic ensembles in free space or atoms coupled to macroscopic Fabry-Perot cavities, which remain difficult to scale up.

In recent years, there has been rapid experimental progress to couple cold atoms to micro- and nanophotonic systems. Such systems offer tremendous potential for scalability and integration, configurability, and in their figures of merit such as mode volume and quality factor. Despite the promise of these systems, however, there are at least two major open questions, which ATOMNANO is focused on addressing. First, techniques to robustly trap and interface cold atoms with complex photonic structures remain inadequately developed, yet are central to the future success of the field. Second, beyond the transfer of previous capabilities of atomic systems onto nanoscale platforms, the potential for realizing fundamentally new applications and observing novel physical phenomena in these systems has hardly been explored.

Within this context, ATOMNANO has pioneered a number of important advances, which both help to facilitate the experimental realization of atom-nanophotonics interfaces and present new visions of the possibilities of such systems. Among the research highlights:

- We have developed both fundamental design principles and computational tools that enable the design of realistic photonic crystal structures, which simultaneously enable the localization of cold atoms near these structures and tuning of atom-photon interactions. These theoretical principles have been directly applied to experiments that now demonstrate the interface of cold atoms with photonic crystal waveguides.

- We have shown that properly designed photonic crystal structures enable the realization of strong, tunable long-range interactions between the internal degrees of freedom of atoms, their motion, and photons propagating in the photonic crystal. The underlying mechanism is based upon a novel phenomenon wherein atoms become dressed by localized photonic “clouds,” whose size can be tailored by either atomic or structural properties. The ability to realize long-range interactions between these various degrees of freedom (spin, motion, and photons) is expected to open up new avenues in the investigation of quantum many-body phenomena with cold atoms.

- We have proposed and analyzed novel phenomena that arise from these long-range interactions. This includes new types of nonlinear optical effects, for example, in which long-range optical interactions can be tuned so that photons bind into “molecules,” and protocols to enable synthesis of arbitrary superpositions of photon Fock states in a single mode. In addition, we have shown that strong spin-dependent forces arising from atoms coupled to photonic crystals can yield exotic “quantum crystals,” in which the spatial patterns and organization of atoms depends on their spin entanglement properties.

- We have developed new theoretical techniques to investigate photon dynamics and atom-atom interactions in complex nanophotonic structures. For example, we have shown that the problem can be reduced to an effective open “spin model” involving the internal degrees of freedom of the atoms, with an interaction strength proportional to the classical electromagnetic Green’s function. Correlation functions of the spins within this model can be used to calculate correlation functions of photons via a generalized input-output formalism.

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