Creating heralded hyper-entangled photons using Rydberg atoms

Entangled photon pairs are a fundamental component for testing the foundations of quantum mechanics,and for modern quantum technologies such as teleportation and secured communication.Current state-of-the-art sources are based on nonlinear processes that are limited in their efficiency and wavelength tunability.This motivates the exploration of physical mechanisms for entangled photon generation,with a special interest in mechanisms that can be heralded,preferably at telecommunications wavelengths.Here we present a mechanism for the generation of heralded entangled photons from Rydberg atom cavity quantum electrodynamics(cavity QED).We propose a scheme to demonstrate the mechanism and quantify its expected performance.The heralding of the process enables non-destructive detection of the photon pairs.The entangled photons are produced by exciting a rubidium atom to a Rydberg state,from where the atom decays via two-photon emission(TPE).A Rydberg blockade helps to excite a single Rydberg excitation while the input light field is more efficiently collectively absorbed by all the atoms.The TPE rate is significantly enhanced by a designed photonic cavity,whose many resonances also translate into high-dimensional entanglement.The resulting high-dimensionally entangled photons are entangled in more than one degree of freedom:in all of their spectral components,in addition to the polarization—forming a hyperentangled state,which is particularly interesting in high information capacity quantum communication.We characterize the photon comb states by analyzing the Hong-Ou-Mandel interference and propose proof-of-concept experiments.