Figure 1: Configuration of experimental apparatus.
A laser-cooled 174Yb+ ion is confined in a radio frequency Paul trap formed by the electric quadrupole (dashed lines) between two tungsten needles. Resonant illumination at λ=369.5 nm is focused to a spot 4.8 μm FWHM and absorbed by the ion. The resulting shadow is imaged with a large-aperture phase Fresnel objective lens onto a cooled CCD camera at ×615 magnification (additional optics omitted for clarity).
