Simultaneous position and state measurement of Rydberg atoms
  We present a technique for state-selective position detection of cold Rydberg atoms. Ground state Rb atoms in a magneto-optical trap are excited to a Rydberg state and are subsequently ionized with a tailored electric field pulse. This pulse selectively ionizes only atoms in e.g. the 54d state and not in the 53d state. The released electrons are detected after a slow flight towards a micro channel plate. From the time of flight of the electrons the position of the atoms is deduced. The state selectivity is about 20:1 when comparing 54d with 53d and the one-dimensional position resolution ranges from 6 to 40 $\mu$m over a range of 300 $\mu$m. This state selectivity and position resolution are sufficient to allow for the observation of coherent quantum excitation transport. 
C. S. E. van Ditzhuijzen, A. F. Koenderink, L. D. Noordam, and H. B.   van Linden van den Heuvell