Experimental Study of the Validity of Entangled Two-Photon Absorption Measurements in Organic Compounds.

Entangled two-photon absorption (ETPA) has recently become a topic of lively debate, mainly due to the apparent inconsistencies in the experimentally reported ETPA cross sections of organic molecules obtained by a number of groups. In this work, we provide a thorough experimental study of ETPA in the organic molecules Rhodamine B (RhB) and zinc tetraphenylporphirin (ZnTPP). Our contribution is 3-fold: first, we reproduce previous results from other groups; second, we on the one hand determine the effects of different temporal correlations─introduced as a controllable temporal delay between the signal and idler photons to be absorbed─on the strength of the ETPA signal, and on the other hand, we introduce two concurrent and equivalent detection systems with and without the sample in place as a useful experimental check; third, we introduce, and apply to our data, a novel method to quantify the ETPA rate based on taking into account the full photon-pair behavior rather than focusing on singles or coincidence counts independently.

Implementation and characterization of a controllable dephasing channel based on coupling polarization and spatial degrees of freedom of light.

We present the experimental implementation and theoretical model of a controllable dephasing quantum channel using photonic systems. The channel is implemented by coupling the polarization and the spatial distribution of light that play, in the perspective of open quantum systems, the role of quantum system and environment, respectively. The capability of controlling our channel allows us to visualize its effects in a quantum system.

Entangled Two Photon Absorption Cross Section on the 808 nm Region for the Common Dyes Zinc Tetraphenylporphyrin and Rhodamine B.

We report the measurement of the entangled two-photon absorption (ETPA) cross section, σ, at 808 nm on organic chromophores in solution in a low photon flux regime. We performed measurements on zinc tetraphenylporphyrin (ZnTPP) in toluene and rhodamine B (RhB) in methanol. This is, to the best of our knowledge, the first time that σ is measured for RhB.

Measuring different types of transverse momentum correlations in the biphoton's Fourier plane.

In this Letter, we present a theoretical and experimental study about the spatial correlations of paired photons generated by Type II spontaneous parametric down-conversion. In particular, we show how these correlations can be positive or negative, depending on the direction in which the far-field plane is scanned and the polarization postselected. Our results provide a straightforward way to observe different kind of correlations that complement other well-known methods to tune the spatial correlations of paired photons.