Final Report Summary - PACART (Free space photon atom coupling - the art of focusing)
In the experiments with a single ion, considerable coupling efficiencies have been achieved as e.g. witnessed by the phase shift of a weak coherent state of light. Furthermore, several technologies for compensating the aberrations of deep parabolic mirrors were explored, leading the path to diffraction limited and therefore most efficient full solid angle (4π) focusing in free space.
The optical trap hosting solid-state quantum targets, which is based on the same design principle as the coupling of light to a single ion, yields trapping performances much better than the ones obtained by standard focusing in free space. The successful verification of single-photon emission from the trapped nanoparticles envisions the realization of an efficient single-photon source build upon technologically relevant solid-state quantum systems.
Along with these experiments on ultimate focusing, several experimental technologies applicable in – but not limited to – coupling single atoms and light in free space were developed. This includes the generation of spectrally shaped single photons by parametric down-conversion in a whispering-gallery-mode resonator and the demonstration of bright squeezed vacuum with tailored spectral properties.