Single quantum dot controls a plasmonic cavity’s scattering and anisotropy

Abstract

Plasmonic cavities represent a promising platform for controlling light-matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light's coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices.optical spectroscopy | hybrid nanostructures | quantum systems | plasmonic cavities | Fano resonance M any quantum network and quantum information processing schemes build upon the enhanced light-matter interaction between a single quantum emitter and a cavity, enabling the effective conversion between photonic and matterbased quantum states (1-4). For example, if the absorption of a photon by a single atom placed inside a cavity can render it transparent to a second photon, then a variety of promising quantum information processing devices can be envisioned including quantum phase gates and repeaters (5). Such QED effects require a high atomic cooperativity c ¼ g 2 γk , where the coupling strength g 2 ∝ 1=V is inversely proportional to the volume of the cavity mode V (6). γ and k are the linewidth of the atomic transition and the cavity mode, respectively. Typically, a high cavity quality factor Q (or low k) of conventional photonic cavities is required to compensate for relatively large (diffraction-limited) mode volumes and comes at a cost: The narrow linewidth of cavity modes places stringent requirements on their spectral alignment with the frequencies of quantum transitions. Plasmonic cavities, on the other hand, achieve high values of C while maintaining moderate Q values because of their ultrasmall modal volume (7-10). The relaxed spectral alignment requirements facilitate the experimental realization of various quantum phenomena, such as collective photon emission from a small ensemble of emitters (11) and single photon sources with tunable statistical properties (12).Prior experiments exploring cavity QED effects associated with single emitters coupled to plasmonic cavities or waveguides focused almost exclusively on the observations of reducing the emitter's lifetime due to the enhanced radiative (propor...

What’s so Hot about Electrons in Metal Nanoparticles?

“…[173][174][175] This quantum regime was only recently observed and reported in Ref. [176]. Experimental spectra versus angle, (b) peak wavelength extracted from the spectra versus angle data.…”

Quantum description and emergence of nonlinearities in strongly coupled single-emitter nanoantenna systems

“…The ability to strongly couple a single QE to a nanoscale plasmonic antenna would be extra beneficial for quantum information processing applications [30][31][32][33]. Although observations of Rabi splitting with ensembles of quantum emitters coupled to plasmonic structures have been widely reported [13,[34][35][36][37][38][39], only a few recent reports claimed observation of Rabi splitting with a single QE [40][41][42][43][44]. Achieving prominent and robust splittings in plasmonic structures is hindered mostly by low-Q factors of such nanocavities-a problem that has been suggested to deal with via structuring the environment of the emitter [45,46].…”

Transformation Optics Approach to Plasmon-Exciton Strong Coupling in Nanocavities

“…From the experimental side, in recent years, PEPs have been reported in emitter ensembles [10][11][12][13], in which excitonic nonlinearities are negligible [14][15][16]. Only very recently, thanks to advances in the fabrication and characterization of large Purcell enhancement nanocavities [17][18][19], far-field signatures of plasmonexciton strong coupling for single molecules have been reported experimentally [20].In this Letter, we theoretically investigate the plasmonic coupling of a single emitter in a paradigmatic cavity: the nanometric gap between two metallic particles [13,19,20]. We consider spherical-shaped nanoparticles, and develop a transformation optics (TO) [21,22] approach that fully accounts for the rich EM spectrum that originates from SP hybridization across the gap.…”

“…From the experimental side, in recent years, PEPs have been reported in emitter ensembles [10][11][12][13], in which excitonic nonlinearities are negligible [14][15][16]. Only very recently, thanks to advances in the fabrication and characterization of large Purcell enhancement nanocavities [17][18][19], far-field signatures of plasmonexciton strong coupling for single molecules have been reported experimentally [20].…”