Nonpeturbative cavity-QED between a single quantum dot and a metal nanoparticle

We investigate the quantum optical properties of an excited single photon emitter (quantum dot) near the surface of a finite-size metal nanoparticle using a photon Green function technique that rigorously quantizes the electromagnetic fields. We obtain Purcell factors of up to 5 x 10(4) due to higher order plasmon modes for both a 7-nm and 20-nm radius metal nanoparticle, and show the failure of employing a dipole approximation in regimes where useful quantum optical interactions occur. We also calculate enormous photonic Lamb shifts of up to 40 meV giving a normalized frequency shift up to broken vertical bar Delta omega broken vertical bar max/omega(d) = 1.28 x 10(-2). Considering a small quantum-dot, positioned 2-nm from the metal nanoparticle surface, we demonstrate that the strong coupling regime should be observable in the far-field spontaneous emission spectrum, even at room temperature and despite the non-propagating nature of the higher order modes. The vacuum Rabi doublet becomes a rich spectral quartet with two of the four peaks anticrossing, and surviving in spite of significant non-radiative decays. We also discuss the role of optical quenching and highlight the importance of accounting for photon transport from the dot to the detector. Our formalism is quite general and can easily be extended to include interactions between multiple quantum dots and multiple metal nanoparticles.