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Photonic integrated circuits provide a compact and stable platform for quantum photonics. Here we demonstrate a silicon photonics quantum key distribution (QKD) encoder in the first high-speed polarization-based QKD field tests. The systems reach composable secret key rates of 1.039 Mbps in a local test (on a 103.6-m fiber with a total emulated loss of 9.2 dB) and 157 kbps in an intercity metropolitan test (on a 43-km fiber with 16.4 dB loss). Our results represent the highest secret key generation rate for polarization-based QKD experiments at a standard telecom wavelength and demonstrate photonic integrated circuits as a promising, scalable resource for future formation of metropolitan quantum-secure communications networks.

We describe a model for metal-polymer interfaces based on the nondegenerate continuum model of Brazovskii and Kirova for the electronic properties of polymers. The correct analytic equations for a bipolaron lattice in this model are stated and the electronic properties of the bulk polymer, i.e., the energy-level structure, the energy density, and the chemical potential as a function of electron density are obtained numerically. We find that the bipolaron lattice is unstable at high densities when the intrinsic gap parameter exceeds a critical fraction of the total energy gap. The electronic properties of the bulk polymer are used for modeling the metal-polymer interface. The charge density near a metal-polymer interface is found from the electrostatic potential and an analytic expression for the bipolaron chemical potential assuming that the contact is in equilibrium with the polymer layer. Poisson's equation is integrated to determine the electrostatic potential. We find that a large charge density is transferred into the polymer layer if the Fermi level of the metal contact is higher than the negative bipolaron formation energy per particle or lower than the positive bipolaron formation energy per particle. The transferred charge lies very close to the metal-polymer interface as a bipolaron lattice with charge density progressively decreasing away from the interface.The transferred charge gives rise to a region of rapid ``band bending,'' pins the Fermi level, and establishes the effective Schottky energy barrier. Upon increasing the metal Fermi level above the bipolaron formation energy per particle, the effective Schottky barrier saturates at the energy difference between the polaron formation energy and the bipolaron formation energy per particle. The model results are useful in interpreting recent measurements of internal photoemission, device electroabsorption, and capacitance-voltage characteristics in polymer light-emitting diodes. \textcopyright{} 1996 The American Physical Society.

The one-dimensional Anderson model with binary distributed onsite disorder is investigated using the transfer-matrix approach. The random matrix product is transformed into an iterated conformal map and the convergence of the mapping is studied for various values of the concentration of onsite impurities and the energy. For dilute impurity concentrations the convergence of the mapping is strongly energy dependent and exhibits interesting behavior in the complex mapping plane. As the impurity concentration increases the mapping converges to the unit circle which results from the underlying conformal structure. Explicit expressions for the Lyapunov exponent and the eigenvalues of the transfer matrix are obtained in terms of the conformal map. From the Lyapunov exponent, the localization length and the integrated density of states are calculated. In the dilute limit there exist states in which the localizaiton length exceeds the system size. These states correspond to extended electronic states and it is shown that the number of extended states scales with system size as ${\mathit{N}}_{\mathrm{extended}}$\ensuremath{\propto}${\mathit{N}}^{\mathrm{\ensuremath{-}}2}$. Increasing the impurity concentration beyond a critical value destroys these states and the localization length over the entire energy range becomes smaller than the system size.

We present an almost fully analytical technique for computing Casimir interactions between periodic lamellar gratings based on a modal approach. Our method improves on previous work on Casimir modal approaches for nanostructures by using the exact form of the eigenvectors of such structures, and computing eigenvalues by solving numerically a simple transcendental equation. In some cases eigenvalues can be solved for exactly, such as the zero frequency limit of gratings modeled by a Drude permittivity. Our technique also allows us to predict analytically the behavior of the Casimir interaction in limiting cases, such as the large separation asymptotics. The method can be generalized to more complex grating structures, and may provide a deeper understanding of the geometry-composition-temperature interplay in Casimir forces between nanostructures., Comment: 16 pages, 7 figures

A meshlike energy structure of collective intersubband excitations and damped collective energy level crossings are predicted for electrons confined on a cylindrical graphitic nanotube. Unusual Kohn anomalies, besides 2${\mathit{k}}_{\mathit{F}}$, are found for nanotubes. Multipole collective excitations are obtained for ${\mathrm{C}}_{60}$ and related quasispherical fullerenes, and the results are in excellent agreement with available experimental measurements.

We develop a discrete plasmonic mode-matching technique to investigate the ultimate limits to plasmonic light concentration down to the length scales required for observation of quantum-mechanical phenomena, including plasmon-assisted electron tunneling. Our mode-matching calculations, verified by direct numerical solution of Maxwell's equations, indicate achievable coupling efficiencies of $g20%$ into symmetric bound gap plasmon modes in sub-10-nm gaps. For a given operating wavelength and a choice of material parameters, we demonstrate the existence of a specific width that maximizes enhancement of the electromagnetic field coupled into the gap. More generally, our calculations establish an intuitive and a computationally efficient framework for determining coupling efficiencies in and out of quantum-scale waveguides.

We present a modal approach to calculate finite temperature Casimir interactions between two periodically modulated surfaces. The scattering formula is used and the reflection matrices of the patterned surfaces are calculated decomposing the electromagnetic field into the natural modes of the structures. The Casimir force gradient from a deeply etched silicon grating is evaluated using the modal approach and compared to experiment for validation. The Casimir force from a two dimensional periodic structure is computed and deviations from the proximity force approximation examined., Comment: 13 pages, 7 figures