Three-photon molecule generation through coherent scattering process off single dipole emitter in quantum nanophotonics

Bound state refers to the quantum state wherein wave function of constituent particles is localized, which typically require interactions between individual particles, e.g., two hydrogen atoms form bound state of a hydrogen molecule due to Coulomb interactions. Thus, photons do not form bound states (also called photonic molecules) easily due to its electric neutrality. Recently, it has been reported that, when three photons interact with a single emitter, photon-photon entanglement mediated by the emitter may induce the formation of 3-photon molecules. However, the underlying generation mechanism is not yet clear.

Here we present a computational study to confirm that, through coherent scattering process for three uncorrelated photons off a single dipole emitter, 3-photon molecule is generated. In particular, three prominent signatures: (1) exponentially decaying wave function as photon distance increases; (2) anti-correlation signature; and (3) pi-phase shift, are unveiled by examining correlation functions and wave functions of scattered photons. Moreover, we show that our results account for recent experiment in ultra-cold atomic gas well. Such a 3-photon molecule has potential applications in designing photonic quantum logic gate and three-photon fluorescence microscopy.