Amplifying single impurities immersed in a gas of ultra cold atoms
  We present a method for amplifying a single or scattered impurities immersed in a background gas of ultra cold atoms so that they can be optically imaged and spatially resolved. Our approach relies on a Raman transfer between two stable atomic hyperfine states that is conditioned on the presence of an impurity atom. The amplification is based on the strong interaction among atoms excited to Rydberg states. We perform a detailed analytical study of the performance of the proposed scheme with particular emphasis on the influence of many-body effects. 
B. Olmos, W. Li, S. Hofferberth, and I. Lesanovsky
cond-mat.quant-gas physics.atom-ph quant-ph