Single-photon sources are subjected to a fundamental limitation in the speed of operation dictated by the spontaneous emission rate of quantum emitters (QEs). The current paradigm of the rate acceleration suggests coupling of a QE to a metal nanostructure, in particular, a metal nanoparticle (MNP). Here, we demonstrate that, in contrast to this approach, a MNP itself being excited via a strong coupling with a QE can emit light with quantum properties. We determine both the first- and second-order correlation functions of light spontaneously emitted by a MNP in such a compound and show that this light should exhibit sub-Poissonian photon statistics and perfect photon antibunching. This discovery opens a prospect to single-photon sources with generation rates up to 100 THz.

• Received 25 July 2019

DOI:https://doi.org/10.1103/PhysRevA.100.063807