Hot-Band Absorption Can Mimic Entangled Two-Photon Absorption.

It has been proposed that entangled two-photon absorption (E2PA) can be observed with up to 10 lower photon flux than its classical counterpart, therefore enabling ultralow-power two-photon fluorescence microscopy. However, there is a significant controversy regarding the magnitude of this quantum enhancement in excitation efficiency. We investigated the fluorescence signals from Rhodamine 6G and LDS798 excited with a CW laser or an entangled photon pair source at ∼1060 nm.

Witnessing the survival of time-energy entanglement through biological tissue and scattering media.

We demonstrate the preservation of the time-energy entanglement of near-IR photons through thick biological media (≤1.55 mm) and tissue (≤ 235 m) at room temperature. Using a Franson-type interferometer, we demonstrate interferometric contrast of over 0.