Studying light-matter interaction with broadband entangled photons (Prof. A. Stefanov)

Theoretical proposals have suggested that energy-entangled photons offer new control parameters for two-photon spectroscopy. Varying entanglement parameters permits to access to virtual states whose energy exceed that of the initial-to-final state transition [B. Saleh, et al., PRL, 80(16), 3483 (1998)], while it is expected that excitation of chromophore aggregates with non-classical light reveals the level structure of the double-exciton manifold [F. Schlawin, et al., PRA, 86(2), 1-10 (2012)]. Broadband energy entangled photons from parametric downconversion are a promising source of quantum light to study such effects. Their wave function can be shaped by techniques similar to the shaping of short laser pulses opening the door to spectroscopy studies. We demonstrate the application of various transfer functions to the entangled photons by simultaneously shaping both phase and amplitude with a pulse shaper based on a spatial light modulator. We show how the two-photon wave function can be characterized by applying interferometric autocorrelation schemes. Additionally we study effects of a dispersive medium on the two photon wave function.Finally broadband energy-entangled photons possess a very large entanglement content, as shown by computing the entropy of entanglement. This entanglement can be used for quantum information processing in high dimensional spaces. We show results of quantum tomography and various Bell inequalities measurements.