Entanglement detection in coupled particle plasmons

Javier del Pino,^1,2 Johannes Feist,¹ F.J. García-Vidal,¹ and Juan José García-Ripoll²

¹Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid E-28049, Spain

²Instituto de Física Fundamental, IFF-CSIC, Calle Serrano 113b, Madrid E-28006, Spain

When in close contact, plasmonic resonances interact and become strongly correlated. We develop a quantum mechanical model for an array of coupled particle plasmons. This model predicts that when the coupling strength between plasmons approaches or surpasses the local dissipation, a sizable amount of entanglement is stored in the collective modes of the array. We also prove that entanglement manifests itself in far-field images of the plasmonic modes, through the statistics of the quadratures of the field, in what constitutes a novel family of entanglement witnesses. Finally, we estimate the amount of entanglement, the coupling strength and the correlation properties for a system that consists of two or more coupled nanospheres of silver, showing evidence that our predictions could be tested using present-day state-of-the-art technology.