Enhancing the production of photonic Cooper pairs from room-temperature Raman scattering

Raman scattering may generate entangled photon pairs when the same excitation created during a Stokes process is annihilated by another incoming photon. This correlated Stokes-anti-Stokes (SaS) process can also occur due to the exchange of virtual phonons and the entangled photon pairs generated in this way are called photonic cooper pairs [1].

So far the SaS experiments are focused on coincidence measurements yielding large zero-time second-order correlation g⁽²⁾(0). While this demonstrates that the SaS process is a nonclassical phenomenon, it does not allow the quantification of entanglement for quantum optics applications. Here we describe a theory that shows that photonic Cooper pairs can be used for the generation of a multimode-squeezed state and heralded single-photon emission.

Our theory predicts the enhancement of photonic Cooper pair generation in the presence of Surface Enhanced Raman Scattering (SERS). Not all SERS enhancement mechanisms favor the generation of photonic cooper pairs at room temperature. Only those tailored to increase the anti-Stokes intensity relative to the Stokes one may lead to efficient entangled photon production.