Generation of nonclassical states using quantum emitters in the metal-dielectric surface

We show that it is possible to generate optical photons in nonclassical states from a metal-dielectric interface using quantum emitters on the interface. The photons thus emitted into the surface plasmon (SP) mode from the initially excited emitters radiate out in free space in a cone-shaped geometry. When detected at two detectors, they exhibit anti-coalescence, a clear signature of nonclassicality. This also indicates that the photons are prepared in the path-entangled N00N-like states. These photons can be used for long-distance communication through free space or fiber. This technique is further scalable to a large number of photons. Such a system can therefore be employed as a building block for a distributed quantum network. We emphasize that our setup is different from the previously reported works in which the emitters get coupled to either propagating SP mode in a nanowire or the guided mode of a nanofiber, instead of the propagating SP mode on the interface. We find that the transmission probability of the photons into the free space is close to 0.7 from a silver-air interface, and therefore it is indeed feasible to implement our model using available technology.