The paper by M. Fleischhauer and M. D. Lukin explores the concept of dark-state polaritons in the context of Electromagnetically Induced Transparency (EIT). Dark-state polaritons are form-stable coupled excitations of light and matter, which can be controlled by an external coherent field. These polaritons exhibit properties such as a group velocity that is determined by the mixing angle between light and matter components. The authors demonstrate that light pulses can be decelerated and "trapped" within the medium, preserving their shape and quantum state as they are mapped onto metastable collective states of matter. This reversible coherent-control technique has potential applications in generating non-classical states of atomic ensembles, reversible quantum memories for light waves, and high-resolution spectroscopy. The paper also discusses the validity of the adiabatic approximation and the effect of Raman coherence decay, providing insights into the practical implementation of these techniques in experiments.The paper by M. Fleischhauer and M. D. Lukin explores the concept of dark-state polaritons in the context of Electromagnetically Induced Transparency (EIT). Dark-state polaritons are form-stable coupled excitations of light and matter, which can be controlled by an external coherent field. These polaritons exhibit properties such as a group velocity that is determined by the mixing angle between light and matter components. The authors demonstrate that light pulses can be decelerated and "trapped" within the medium, preserving their shape and quantum state as they are mapped onto metastable collective states of matter. This reversible coherent-control technique has potential applications in generating non-classical states of atomic ensembles, reversible quantum memories for light waves, and high-resolution spectroscopy. The paper also discusses the validity of the adiabatic approximation and the effect of Raman coherence decay, providing insights into the practical implementation of these techniques in experiments.