Entanglement Generation by Time Varying Refractive Index: Analogy with Cosmological Model

Generation of entanglement between modes of a electromagnetic fields by sudden change of the refractive index of a medium is considered. We use the analogy between the Fock-space formulation of pair creation caused by the contraction and expansion of the universe on one hand and the pair creation in time-dependent electric fields on the other hand. It is shown that entanglement between photons encodes information concerning the underlying refractive index of a medium.