Quantum dense coding over Bloch channels

Dynamics of coded information over Bloch channels is investigated for different values of the channel's parameters. We show that, the suppressing of the travelling coded information over Bloch channel can be increased by decreasing the equilibrium absolute value of information carrier and consequently decreasing the distilled information by eavesdropper. The amount of decoded information can be improved by increasing the equilibrium values of the two qubits and decreasing the ratio between longitudinal and transverse relaxation times. The robustness of coded information in maximum and partial entangled states is discussed. It is shown that the maximum entangled states are more robust than the partial entangled state over this type of channels

Entanglement enhanced classical capacity of quantum communication channels with correlated noise in arbitrary dimensions

We study the capacity of d-dimensional quantum channels with memory modeled by correlated noise. We show that, in agreement with previous results on Pauli qubit channels, there are situations where maximally entangled input states achieve higher values of mutual information than product states. Moreover, a strong dependence of this effect on the nature of the noise correlations as well as on the parity of the space dimension is found. We conjecture that when entanglement gives an advantage in terms of mutual information, maximally entangled states saturate the channel capacity.Comment: 10 pages, 5 figure

General theory for decoy-state quantum key distribution with arbitrary number of intensities

We develop a general theory for quantum key distribution (QKD) in both the forward error correction and the reverse error correction cases when the QKD system is equipped with phase-randomized coherent light with arbitrary number of decoy intensities. For this purpose, generalizing Wang's expansion, we derive a convex expansion of the phase-randomized coherent state. We also numerically check that the asymptotic key generation rates are almost saturated when the number of decoy intensities is three.Comment: This manuscript has been revised extensivel

Lieb-Thirring Bound for Schr\"odinger Operators with Bernstein Functions of the Laplacian

A Lieb-Thirring bound for Schr\"odinger operators with Bernstein functions of the Laplacian is shown by functional integration techniques. Several specific cases are discussed in detail.Comment: We revised the first versio

Geometry of entangled states

Geometric properties of the set of quantum entangled states are investigated. We propose an explicit method to compute the dimension of local orbits for any mixed state of the general K x M problem and characterize the set of effectively different states (which cannot be related by local transformations). Thus we generalize earlier results obtained for the simplest 2 x 2 system, which lead to a stratification of the 6D set of N=4 pure states. We define the concept of absolutely separable states, for which all globally equivalent states are separable.Comment: 16 latex pages, 4 figures in epsf, minor corrections, references updated, to appear in Phys. Rev.

Predicting bushmeat biomass from species composition captured by camera traps: Implications for locally based wildlife monitoring

アフリカ熱帯雨林における野生動物資源量推定の有効な指標を発見 --地域住民主体の野生動物モニタリング法の基礎を確立--. 京都大学プレスリリース. 2022-08-26.Cameras candidly capture bushmeat mammals to avert crisis. 京都大学プレスリリース. 2022-08-30.1. Facing the bushmeat crisis, tropical forests require effective monitoring for sustainable wildlife management. To gain credibility with local people and conservation officials, the monitoring needs indicators that comply with local knowledge and predict the available faunal resources. 2. This study explores predictive indicators for bushmeat biomass --the total biomass of five main hunted mammals-- in a Cameroonian rainforest. We employed camera trapping and the Random Encounter and Staying Time (REST) model to estimate the spatial variation in each species' population density and bushmeat biomass at three sites. We then calculated six indicators from camera-trap capture rate estimates and assessed their predictive performance for the total wild meat amount. 3. Duikers generally increased with distance from the public road, but two red duiker species were more markedly affected by the distance than blue duikers. Spatial density patterns of brush-tailed porcupines and Emin's pouched rats differed between sites. Consequently, bushmeat biomass displayed exponential growth away from the road with varying degrees among the sites. 4. Of the six indicators, the R/B ratio (red-to-blue duiker ratio) and the D/R ratio (duiker-to-rodent ratio) exhibited positive linear-like correlations to bushmeat biomass at all sites. The correlation lines were moderately similar across sites in the R/B ratio but largely different in the D/R ratio, suggesting that the latter is unsuitable for sharing information between neighbouring communities. 5. Synthesis and applications. The two indicators based on captured animal composition may effectively predict the total biomass of the main target species for bushmeat hunting, given a reasonably large sample size. The R/B ratio (red duikers/blue duikers) is recommended as a first choice; the D/R ratio (duikers/rodents) can be a good alternative when information sharing is not essential. Because local hunters are aware of depletion-related changes in species composition of caught animals, these indices may be effectively incorporated into community-based wildlife monitoring.1. Face à la crise de la viande de brousse, les forêts tropicales nécessitent un système de suivi efficace pour une gestion durable de la faune. Pour gagner en crédibilité auprès des populations locales et des responsables de la conservation, le suivi a besoin d'indicateurs qui respectent les connaissances locales et prédisent les ressources fauniques disponibles. 2. Cette étude explore des indicateurs prédictifs de la biomasse de la viande de brousse --la biomasse totale de cinq principaux mammifères chassés-- dans une forêt tropicale camerounaise. Nous avons utilisé des caméra-piège et le modèle REST (Random Encounter and Staying Time) pour estimer la variation spatiale de la densité de chaque espèce et de la biomasse de viande de brousse sur trois sites. Nous avons ensuite calculé six indicateurs à partir des estimations du taux de capture par caméra-piège et évalué leur performance prédictive pour la quantité totale de viande sauvage. 3. Le nombre de céphalophes augmentaient généralement avec la distance de la route publique, mais deux espèces de céphalophes roux étaient plus fortement affectés par la distance que les céphalophes bleus. Les modèles de densité spatiale des porcs-épics et des rats géants d'Emin différaient selon les sites. Par conséquent, la biomasse de viande de brousse a affiché une croissance exponentielle en s'éloignant de la route, avec des degrés variables selon les sites. 4. Parmi les six indicateurs, le ratio R/B (le ratio des céphalophes rouges par rapport aux céphalophes bleus) et le ratio D/R (le ratio des céphalophes par rapport aux rongeurs) présentaient des corrélations linéaires avec la biomasse de viande de brousse sur tous les sites. Les lignes de corrélation étaient modérément similaires d'un site à l'autre pour le ratio R/B mais largement différentes pour le ratio D/R, ce qui suggère que ce dernier n'est pas approprié pour le partage d'informations entre communautés adjacentes. 5. Synthèse et applications. Les deux indicateurs basés sur la composition des animaux capturés peuvent prédire efficacement la biomasse totale des principales espèces cibles de la chasse à la viande de brousse, à condition de disposer d'une taille d'échantillon raisonnablement importante. Le ratio R/B (les céphalophes rouges/bleus) est recommandé comme premier choix; le ratio D/R (les céphalophes/les rongeurs) peut être une bonne alternative lorsque le partage des informations n'est pas essentiel. Comme les chasseurs locaux sont conscients des changements liés à l'épuisement dans la composition des espèces des animaux capturés, ces indicateurs peuvent être efficacement intégrés dans le suivi communautaire de la faune

Majorization properties of generalized thermal distributions

We examine the majorization properties of general thermal-like mixed states depending on a set of parameters. Sufficient conditions which ensure the increase in mixedness, and hence of any associated entropic form, when these parameters are varied, are identified. We then discuss those exhibiting a power law distribution, showing that they can be characterized by two distinct mixing parameters, one associated with temperature and the other with the non-extensivity index q. Illustrative numerical results are also provided.Comment: 11 pages, 1 figure. Some references adde