Graphene as a source of entangled plasmons

We analyze nonlinear optics schemes for generating pairs of quantum entangled plasmons in the terahertz-infrared range graphene. predict that high plasmonic field concentration and strong optical nonlinearity monolayer graphene enables pair-generation rates much higher than those conventional photonic sources. The first scheme we study is spontaneous parametric down conversion a nanoribbon. In this second-order process plasmon excited by an external pump splits into pair plasmons, half original frequency each, emitted opposite directions. activated applying dc electric induces density gradient or current across ribbon. Another degenerate four-wave mixing where counter-propagating are at frequency. This third-order does not require symmetry-breaking field. suggest nano-optical experiments measuring position-momentum entanglement pairs. estimate critical fields which generation exceed their dissipation, leading to instabilities.