Enhanced Entangled-Photon-Pair Interaction with Metallic Nanoparticles

In recent years, many quantum light based applications were suggested, reaching beyond classical limitations. Some of these applications, e.g. nonlinear spectroscopy, require the use of entangled-photon-pair interaction (EPPI) with matter. However, such pairs, generated through spontaneous parametric down-conversion (SPDC), are scarce and their interaction with matter is very weak and barely detectable. Thus, an enhancement of this interaction is of great importance.

In this research, we investigate a novel way to achieve such enhanced EPPI using metallic nanoparticles (NPs), which are known for their exceptional capability of light-matter coupling at their localized surface plasmon resonance (LSPR). We present a way of theoretically estimating the rate of EPPI with metallic NPs, based on a simple method of classical light second-harmonic generation (SHG) measurements. Experimental results, obtained for a solution of silver NPs (SNPs), show an estimated four orders-of-magnitude EPPI enhancement, relative to the best organic molecules, and indicate that use of SNPs can be highly advantageous for realization of advanced quantum light schemes.