We consider a subcarrier wave quantum key distribution (QKD) system, where quantum encoding is carried out at weak sidebands generated around a coherent optical beam as a result of electro-optical phase modulation. We study security of two protocols, B92 and BB84, against one of the most powerful attacks for this class of systems, the collective beam-splitting attack. Our analysis includes the case of high modulation index, where the sidebands are essentially multimode. We demonstrate numerically and experimentally that a subcarrier wave QKD system with realistic parameters is capable of distributing cryptographic keys over large distances in presence of collective attacks. We also show that BB84 protocol modification with discrimination of only one state in each basis performs not worse than the original BB84 protocol in this class of QKD systems, thus significantly simplifying the development of cryptographic networks using the considered QKD technique.

We theoretically study electro-optic light modulation based on a quantum model where the linear electrooptic effect and the externally applied microwave field result in the interaction between optical cavity modes. The model assumes that the number of interacting modes is finite and effects of the mode overlapping coefficient on the strength of the intermode interaction can be taken into account through dependence of the coupling coefficient on the mode characteristics. We show that, under certain conditions, the model is exactly solvable and can be analyzed using the technique of the Jordan mappings for the su(2) Lie algebra. Analytical results are applied to study effects of light modulation on the frequency dependence of the photon counting rate. In contrast to the limiting case of infinitely large number of interacting modes, when the number of interacting modes is finite, the sideband intensities reveal strongly nonmonotonic behavior supplemented with asymmetry of the intensity distribution provided the pumped mode is not central. We also analyze different regimes of two-modulator transmission and establish the conditions of validity of the semiclassical approximation by applying the methods of polynomially deformed Lie algebras for analysis of the model with quantized microwave field.

An algebraic method is introduced for an analytical solution of the eigenvalue problem of the Tavis-Cummings (TC) Hamiltonian, based on polynomially deformed su(2), i.e. sun(2), algebras. In this method the eigenvalue problem is solved in terms of a specific perturbation theory, developed here up to third order. Generalization to the N -atom case of the Rabi frequency and dressed states is also provided. A remarkable enhancement of spontaneous emission of N atoms in a resonator is found to result from collective effects.

No abstract

Two-dimensional photonic crystal structures (PCS) were fabricated using a one-step recording process, multi-beam interference in smart polymer nanocomposites incorporating SiO2 and Au nanoparticles sensitized to 532 nm laser radiation. It was shown, that PCS with different geometry can be recorded in thick nanocomposite layers. The typical two dimensional (2D) PCS have square structure with 2-8 µm period, being in good agreement with theoretical structures obtained by mathematical modeling of the recorded PCS. The peculiarities of the photo-polymerization of nanocomposites with plasmonic Au nanoparticles were analyzed on the basis of Surface Plasmon Resonance Imaging (SPRi) and Raman spectroscopy investigations and used for the interpretation of the recording process and periodic structure formation. Abstract Two-dimensional photonic crystal structures (PCS) were fabricated using a one-step recording process, multi-beam interference in smart polymer nanocomposites incorporating SiO 2 and Au nanoparticles sensitized to 532 nm laser radiation. It was shown, that PCS with different geometry can be recorded in thick nanocomposite layers. The typical two dimensional (2D) PCS have square structure with 2-8 µm period, being in good agreement with theoretical structures obtained by mathematical modeling of the recorded PCS. The peculiarities of the photopolymerization of nanocomposites with plasmonic Au nanoparticles were analyzed on the basis of Surface Plasmon Resonance Imaging (SPRi) and Raman spectroscopy investigations and used for the interpretation of the recording process and periodic structure formation.