Two-Photon Absorption Spectroscopy using Intense Phase-Chirped Entangled   Beams
  We numerically analyze the use of intense entangled twin beams for ultra-sensitive spectroscopic measurements in chemical and biological systems. The examined scheme makes use of intense frequency-modulated (chirped) entangled beams to successfully extract information about the intermediate material states that contribute to the two-photon excitation of an absorbing medium. Robustness of the presented method is examined with respect to the applied intervals of the frequency chirp. 
Ji\v{r}\'i Svozil\'ik, Jan Pe\v{r}ina Jr., Roberto de J.   Le\'on-Montiel
quant-ph physics.atom-ph