Vibrational Hyper-Raman Molecular Spectroscopy With Entangled Photons

Time-energy entangled photons produced by spontaneous parametric down-conversion (SPDC) are employed to calculate vibrational hyper-Raman (HR) signals of the conjugated organic chromophore Wu112. Compared with classical light, time-energy entanglement can provide selectivity of Liouville-space pathways and thus suppress the strong broad electronic-Raman background arising from one-photon resonances of the intermediate states. The entangled-photon HR signal scales linearly with the SPDC pump field intensity rather than quadratically for classical light, which allows weak-field measurements on fragile samples.