Complete elimination of information leakage in continuous-variable quantum communication channels

In all lossy communication channels realized to date, information is inevitably leaked to a potential eavesdropper. Here we present a communication protocol that does not allow for any information leakage to a potential eavesdropper in a purely lossy channel. By encoding information into a restricted Gaussian alphabet of squeezed states we show, both theoretically and experimentally, that the Holevo information between the eavesdropper and the intended recipient can be exactly zero in a purely lossy channel while minimized in a noisy channel. This result is of fundamental interest, but might also have practical implications in extending the distance of secure quantum key distribution.Comment: 9 pages, 5 figure

Light-by-light scattering sum rules constraining meson transition form factors

Relating the forward light-by-light scattering to energy weighted integrals of the \gamma* \gamma -fusion cross sections, with one real photon (\gamma) and one virtual photon (\gamma*), we find two new exact super-convergence relations. They complement the known super-convergence relation based on the extension of the GDH sum rule to the light-light system. We also find a set of sum rules for the low-energy photon-photon interaction. All of the new relations are verified here exactly at leading order in scalar and spinor QED. The super-convergence relations, applied to the \gamma* \gamma -production of mesons, lead to intricate relations between the \gamma \gamma -decay widths or the \gamma* \gamma -transition form factors for (pseudo-) scalar, axial-vector and tensor mesons. We discuss the phenomenological implications of these results for mesons in both the light-quark sector and the charm-quark sector.Comment: 32 pages, 7 figure

Точный колебательно-вращательный анализ вращательных полос в диапазоне спектра 1100-1400 СМ-1 молекулы C2HD3

В настоящей работе представляются результаты исследования колебательно- вращательных спектров молекулы C2HD3 в диапазоне 1100 - 1400 см-1. Экспериментальные спектры были зарегистрированы в Техническом Университете Брауншвейга (Германия) с разрешением 0,0021 см- 1. На основе комбинационных разностей, полученных из анализа полос v8 и v12, улучшены параметры основного колебательного состояния. Новый набор спектроскопических параметров, позволил идентифицировать в экспериментальном спектре около 1900 переходов полосы v12. Анализ полосы v12 позволяет так же найти комбинационные полосы 2v10, v7 + v10 и v4 + v10, проявляющиеся в спектре поглощения за счет сильных резонансных взаимодействий

Multiphoton communication in lossy channels with photon-number entangled states

We address binary and quaternary communication channels based on correlated multiphoton two-mode states of radiation in the presence of losses. The protocol are based on photon number correlations and realized upon choosing a shared set of thresholds to convert the outcome of a joint photon number measurement into a symbol from a discrete alphabet. In particular, we focus on channels build using feasible photon-number entangled states (PNES) as two-mode coherently-correlated (TMC) or twin-beam (TWB) states and compare their performances with that of channels built using feasible classically correlated (separable) states. We found that PNES provide larger channel capacity in the presence of loss, and that TWB-based channels may transmit a larger amount of information than TMC-based ones at fixed energy and overall loss. Optimized bit discrimination thresholds, as well as the corresponding maximized mutual information, are explicitly evaluated as a function of the beam intensity and the loss parameter. The propagation of TMC and TWB in lossy channels is analyzed and the joint photon number distribution is evaluated, showing that the beam statistics, either sub-Poissonian for TMC or super-Poissonian for TWB, is not altered by losses. Although entanglement is not strictly needed to establish the channels, which are based on photon-number correlations owned also by separable mixed states, purity of the support state is relevant to increase security. The joint requirement of correlation and purity individuates PNES as a suitable choice to build effective channels. The effects of losses on channel security are briefly discussed.Comment: 8 pages, 19 figure

Multilayer and high-entropy alloy-based protective coatings for solving the issue of critical raw materials in the aerospace industry

Aerospace is an actively developing industry that continuously requires the implementation of modern technologies. The rapid growth in new vehicle production demands much support. Hence, the problem of resources with complicated supply and distribution is always of current interest. These critical raw materials (CRMs) are involved in almost all areas of aerospace manufacturing and service. An efficient and profitable solution to the problem of critical materials can be found in protective coatings, especially in such advanced concepts as multilayer and high-entropy alloy (HEA)-based coatings. In this paper, we study both ways of manufacturing effective coatings. We have shown that multilayer CrN/MoN coatings with exceptional toughness and hardness could find promising applications in the aerospace industry. The developed strategy for the novel materials screening based on the prediction of their properties has been demonstrated on the example of the refractory HEA-based coatings. A brief state of the art of the EU critical raw materials and their place in the aerospace/defence industry has been given.The study has been partially supported and funded by the Ukrainian state budget via the project “Improved Physical and Mechanical Properties of Multilayer Protective Coatings Based on High Entropy Alloy Nitrides” (project № 0120U100475

Sleep in Kcna2 knockout mice

<p>Abstract</p> <p>Background</p> <p><it>Shaker </it>codes for a <it>Drosophila </it>voltage-dependent potassium channel. Flies carrying <it>Shaker </it>null or hypomorphic mutations sleep 3–4 h/day instead of 8–14 h/day as their wild-type siblings do. Shaker-like channels are conserved across species but it is unknown whether they affect sleep in mammals. To address this issue, we studied sleep in <it>Kcna2 </it>knockout (KO) mice. <it>Kcna2 </it>codes for Kv1.2, the alpha subunit of a Shaker-like voltage-dependent potassium channel with high expression in the mammalian thalamocortical system.</p> <p>Results</p> <p>Continuous (24 h) electroencephalograph (EEG), electromyogram (EMG), and video recordings were used to measure sleep and waking in <it>Kcna2 </it>KO, heterozygous (HZ) and wild-type (WT) pups (P17) and HZ and WT adult mice (P67). Sleep stages were scored visually based on 4-s epochs. EEG power spectra (0–20 Hz) were calculated on consecutive 4-s epochs. KO pups die by P28 due to generalized seizures. At P17 seizures are either absent or very rare in KO pups (< 1% of the 24-h recording time), and abnormal EEG activity is only present during the seizure. KO pups have significantly less non-rapid eye movement (NREM) sleep (-23%) and significantly more waking (+21%) than HZ and WT siblings with no change in rapid eye movement (REM) sleep time. The decrease in NREM sleep is due to an increase in the number of waking episodes, with no change in number or duration of sleep episodes. Sleep patterns, daily amounts of sleep and waking, and the response to 6 h sleep deprivation are similar in HZ and WT adult mice.</p> <p>Conclusion</p> <p>Kv1.2, a mammalian homologue of Shaker, regulates neuronal excitability and affects NREM sleep.</p

Modulation leakage vulnerability in continuous-variable quantum key distribution

Flaws in the process of modulation, or encoding of key bits in the quadratures of the electromagnetic light field, can make continuous-variable quantum key distribution systems susceptible to leakage of secret information. Here, we report such a modulation leakage vulnerability in a system that uses an optical in-phase and quadrature modulator to implement a single sideband encoding scheme. The leakage arises from the limited suppression of a quantum-information-carrying sideband during modulation. Based on the results from a proof-of-concept experiment, we theoretically analyse the impact of this vulnerability. Our results indicate that the leakage reduces the range over which a positive secret key can be obtained, and can even lead to a security breach if not properly taken into account. We also study the effectiveness of additional trusted noise as a countermeasure to this vulnerability.Comment: 12 pages, 6 figure

Casimir forces between cylinders at different temperatures

We study Casimir interactions between cylinders in thermal non-equilibrium, where the objects as well as the environment are held at different temperatures. We provide the general formula for the force, in a one reflection approximation, for cylinders of arbitrary radii and optical properties. As is the case for equilibrium, we find that the force for optically diluted cylinders can be obtained by appropriate summation of the corresponding result for spheres. We find that the non-equilibrium forces are generally larger than their equilibrium counterpart at separations greater than the thermal wavelength. They may also exhibit oscillations as function of separation, leading to stable points of zero net force. These effects are particularly pronounced for thin conducting cylinders (e.g. 40nm diameter nano-wires of tungsten) due to their large emissivity.Comment: 10 pages, 5 figure