We investigate qubit-qubit entanglement mediated by plasmons supported by one-dimensional waveguides. We explore both the situation of spontaneous formation of entanglement from an unentangled state and the emergence of driven steady-state entanglement under continuous pumping. In both cases, we show that large values for the concurrence are attainable for qubit-qubit distances larger than the operating wavelength by using plasmonic waveguides that are currently available.

In this Letter we show that a single rectangular hole exhibits transmission resonances that appear near the cutoff wavelength of the hole waveguide. For light polarized with the electric field pointing along the short axis, it is shown that the normalized-to-area transmittance at resonance is proportional to the ratio between the long and short sides, and to the dielectric constant inside the hole. Importantly, this resonant transmission process is accompanied by a huge enhancement of the electric field at both entrance and exit interfaces of the hole. These findings open the possibility of using rectangular holes for spectroscopic purposes or for exploring non-linear effects.

We show how both the subwavelength confinement associated with surface plasmons and the one-dimensional character of plasmonic waveguides can be exploited to enhance the coupling between quantum emitters. Resonance energy transfer and the phenomenon of superradiance are investigated in three different waveguiding schemes (wires, wedges, and channels) by means of the Finite Element Method. We also develop a simplified model that is able to capture the main features of the numerical results.

We study theoretically electromagnetic modes guided by metallic wedges at telecom wavelengths. These modes are found to exhibit superior confinement while showing similar propagation loss as compared to other subwavelength guiding configurations. It is also shown that mode focusing can be realized by gradual modification of the wedge geometry along the mode propagation direction.

We demonstrate that textured closed surfaces, i.e., particles made of perfect electric conductors (PECs), are able to support localized electromagnetic resonances with properties resembling those of localized surface plasmons (LSPs) in the optical regime. Because of their similar behavior, we name these types of resonances as spoof LSPs. As a way of example, we show the existence of spoof LSPs in periodically textured PEC cylinders and the almost perfect analogy to optical plasmonics. We also present a metamaterial approach that captures the basic ingredients of their electromagnetic response. DOI: 10.1103/PhysRevLett.108.223905 PACS numbers: 42.25.Àp, 73.20.Mf, 78.20.Bh, 81.05.Xj In recent years, plasmonics has attracted a great deal of attention due to the possibility of subwavelength confinement and concomitant enhancement of the electromagnetic (EM) field at metal-dielectric interfaces [1][2][3]. Surface plasmons exist either as propagating surface plasmon polaritons (SPPs) for extended interfaces and waveguide configurations or as localized surface plasmons (LSPs) in structures with closed surfaces, i.e., particles [4]. Common to these surface modes is a list of promising applications taking advantage of their subwavelength nature. For example, SPPs are excellent candidates for miniaturization of photonic circuits [5], whereas LSPs have been used in near-field optics [6], surface-enhanced spectroscopy [7][8][9], plasmonic antennas [10,11], and photovoltaics [12,13] due to the field enhancement (FE) occurring at the LSP resonance. On a more fundamental level, it has been shown that both LSPs and SPPs are able to enhance light-matter interaction at the subwavelength scale [14,15]. As subwavelength confinement of surface plasmons relies on the penetration of the EM field into the metal, its usage is inevitably limited to visible or near-infrared frequencies. At lower frequencies, metals sustain EM modes that are weakly bound and thus behave akin to perfect electric conductors (PECs), which do not support surface plasmons.To export the exciting properties of surface plasmons to low frequencies (far infrared, terahertz or microwave), the concept of spoof surface plasmons was developed [16,17]. In contrast to conventional SPPs, spoof surface plasmons also exist in the PEC limit since they are geometry-induced bound EM modes that arise when a metal surface is periodically textured on a subwavelength scale. Spoof SPPs with subwavelength transverse confinement have been found both in periodic perforated plane surfaces [16][17][18][19][20] and in a variety of structured waveguide configurations [21][22][23][24]. In this Letter, we extend the concept of designer plasmons by demonstrating the existence of spoof localized surface plasmons (spoof-LSPs) in periodically textured PEC particles both in two and three dimensions. To illustrate our finding, we show that an almost perfect analogy exists between the EM response of a structured two-dimensional (2D) PEC cylinder and that of a regular metallic cylinder with a Dr...