Atoms in photonic traps
The ATOMNANO (Quantum interface between atomic and nano-photonic systems) project was inspired by the prospect of controlling both type and range of atom-photon interactions. Moreover, by engineering the optical dispersion of photonic crystals, it is possible to achieve strong interactions between individual photons. Photonic crystals are dielectric materials containing nanoscopic elements in a periodic arrangement. Certain wavelengths of light propagate through them, while other wavelengths do not. By carefully designing their periodicity, control of light has been achieved in photonic crystals acting as low-loss waveguides. In ATOMNANO, researchers developed a suite of computational tools for the design of photonic crystals that facilitate the localisation of cold atoms in their structure. Furthermore, they applied new design principles to demonstrate how interactions between atoms and photons propagating in the crystals can be tuned. Specifically, they showed that properly designed photonic crystal structures support strong long-range interactions. A phenomenon wherein atoms are ‘dressed’ in a localised photonic cloud was found responsible. In addition, the cloud size can be tailored by adjusting the crystal structure properties. Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. The ability to realise long-range interactions between atoms and photons also unlocks new avenues in the investigation of quantum many-body physics. Before the completion of ATOMNANO, strong spin-dependent forces arising from atoms coupled to photonic crystals were shown to yield ‘quantum crystals’. In these exotic crystals, the spatial organisation of atoms depends on their spin exchange energies.
Keywords
Ultracold atoms, nanophotonics, photonic crystal, ATOMNANO, many-body physics