A far-off-resonance optical trap for a Ba+ ion

Optical trapping and ions combine unique advantages of independently striving fields of research. Light fields can form versatile potential landscapes, such as optical lattices, for neutral and charged atoms, while avoiding detrimental implications of established radiofrequency traps. Ions interact via long-range Coulomb forces and permit control and detection of their motional and electronic states on the quantum level. Here we show optical trapping of 138Ba+ ions in the absence of radio-frequency fields via a far-detuned dipole trap, suppressing photon scattering by three orders of magnitude and the related recoil heating by four orders of magnitude. To enhance the prospects for optical as well as hybrid traps, we demonstrate a method for stray electric field compensation to a level below 9 mV m−1. Our results will be relevant, for example, for ion–atom ensembles, to enable 4–5 orders of magnitude lower common temperatures, accessing the regime of ultracold interaction and chemistry, where quantum effects are predicted to dominate.