Entangled-Photon Virtual-State Spectroscopy
Bahaa E. A. Saleh, Bradley M. Jost, Hong-Bing Fei, Malvin Carl Teich · Physical Review Letters · 1998
A new form of absorption spectroscopy is introduced in which the energy levels and matrix elements of virtual-state transitions in a medium are determined by the use of continuous-wave degenerate entangled photons without varying their wavelengths. Extractable spectroscopic information is embedded in the entangled-photon absorption cross section when measured over a range of entanglement and interbeam-delay times. This technique exploits the fundamental quantum interference that arises during the interaction of an entangled quantum state with a quantum system.