Quadratic Bell inequalities as tests for multipartite entanglement

This letter presents quantum mechanical inequalities which distinguish, for systems of $N$ spin-\half particles ($N>2$), between fully entangled states and states in which at most $N-1$ particles are entangled. These inequalities are stronger than those obtained by Gisin and Bechmann-Pasquinucci [Phys.\ Lett. A {\bf 246}, 1 (1998)] and by Seevinck and Svetlichny [quant-ph/0201046].Comment: 4 pages, including 1 figure. Typo's removed and one proof simplified in revised versio

Monogamy of Correlations vs. Monogamy of Entanglement

A fruitful way of studying physical theories is via the question whether the possible physical states and different kinds of correlations in each theory can be shared to different parties. Over the past few years it has become clear that both quantum entanglement and non-locality (i.e., correlations that violate Bell-type inequalities) have limited shareability properties and can sometimes even be monogamous. We give a self-contained review of these results as well as present new results on the shareability of different kinds of correlations, including local, quantum and no-signalling correlations. This includes an alternative simpler proof of the Toner-Verstraete monogamy inequality for quantum correlations, as well as a strengthening thereof. Further, the relationship between sharing non-local quantum correlations and sharing mixed entangled states is investigated, and already for the simplest case of bi-partite correlations and qubits this is shown to be non-trivial. Also, a recently proposed new interpretation of Bell's theorem by Schumacher in terms of shareability of correlations is critically assessed. Finally, the relevance of monogamy of non-local correlations for secure quantum key distribution is pointed out, although, and importantly, it is stressed that not all non-local correlations are monogamous.Comment: 12 pages, 2 figures. Invited submission to a special issue of Quantum Information Processing. v2: Published version. Open acces

Approximate quantum cloning and the impossibility of superluminal information transfer

We show that nonlocality of quantum mechanics cannot lead to superluminal transmission of information, even if most general local operations are allowed, as long as they are linear and trace preserving. In particular, any quantum mechanical approximate cloning transformation does not allow signalling. On the other hand, the no-signalling constraint on its own is not sufficient to prevent a transformation from surpassing the known cloning bounds. We illustrate these concepts on the basis of some examples.Comment: 4 pages, 1eps figur

Production and detection of three-qubit entanglement in the Fermi sea

Building on a previous proposal for the entanglement of electron-hole pairs in the Fermi sea, we show how 3 qubits can be entangled without using electron-electron interactions. As in the 2-qubit case, this electronic scheme works even if the sources are in (local) thermal equilibrium -- in contrast to the photonic analogue. The 3 qubits are represented by 4 edge-channel excitations in the quantum Hall effect (2 hole excitations plus 2 electron excitations with identical channel index). The entangler consists of an adiabatic point contact flanked by a pair of tunneling point contacts. The irreducible 3-qubit entanglement is characterized by the tangle, which is expressed in terms of the transmission matrices of the tunneling point contacts. The maximally entangled Greenberger-Horne-Zeilinger (GHZ) state is obtained for channel-independent tunnel probabilities. We show how low-frequency noise measurements can be used to determine an upper and lower bound to the tangle. The bounds become tighter the closer the electron-hole state is to the GHZ state.Comment: 8 pages including 4 figures; [2017: fixed broken postscript figures

Bell inequalities and distillability in N-quantum-bit systems

The relation between Bell inequalities with two two-outcome measurements per site and distillability is analyzed in systems of an arbitrary number of quantum bits. We observe that the violation of any of these inequalities by a quantum state implies that pure-state entanglement can be distilled from it. The corresponding distillation protocol may require that some of the parties join into several groups. We show that there exists a link between the amount of the Bell inequality violation and the size of the groups they have to form for distillation. Thus, a strong violation is always sufficient for full N-partite distillability. This result also allows for a security proof of multi-partite quantum key distribution (QKD) protocols.Comment: REVTEX, 12 pages, two figure

Trophic Relationships and Food Supply of Heterotrophic Animals in the Pelagic Ecosystem of the Black Sea

During recent decades, the Black Sea has been affected by many negative factors that strongly changed the condition of its ecosystem. Especially trophic relationships in the Black Sea pelagic system became very vulnerable influencing the food supply, productivity and abundance of many species and populations of this marine basin. Food is one of most important link between biota and its environment. In this monograph, the role and variability of trophodynamic processes that effect the well-being (health) of main heterotrophic components of ecosystem were analysed in detail for a few key species as indicators for estimation of ecosystem condition in whole. These are most significant mass species of the Black Sea pelagic ecosystem. Among copepods this is Calanus euxinus that dominates the mesozooplankton which makes up the fodder base of planktivorous fishes. Among gelatinous these are medusa Aurelia aurita and the alien ctenophores Mnemiopsis leidyi and Beroe ovata which affected strongly mesozooplankton composition. Lastly among fishes the anchovy Engraulis encrasicolus ponticus and sprat Sprattus sprattus phalericus that dominate small pelagic fishery. We considered in this monograph: • Diel feeding behaviour, in situ feeding rate of Calanus euxinus and impact of mesozooplankton on primary production and phytoplankton biomass. • The effect of vertical migrations on energy budget and its components in C. euxinus; metabolic substrates used in catabolic processes under both aerobic and hypoxic conditions, the role of reserve lipids and effect of abiotic factors on individual growth and population structure of this species. • The intensity and efficiency of ingestion and energy transformation in three gelatinous species ( jellyfish Aurelia aurita, ctenophores Mnemiopsis leidyi and Beroe ovata) and their predatory impact on zooplankton community. • Nutritional condition and food supply of anchovy and sprat in the close interaction with natural biotic and abiotic and anthropogenic factors. • Tendencies in this interaction during long time space: since 1960 s till present years. • Estimation of population condition of these species and its long-term change. This monograph is the collective work of Ukrainian and Turkish scientists studying complex hydrobiological problems of the Black Sea. Its aim is to reveal the significance of nutritional factors on the ecology of Black Sea biota, including changes which have already occurred, as well as offering some insight into changes that may happen in the future. Our joint investigations started in the first half of the 1990s, when conditions for the close cooperation of researchers from the two countries were suitable after the collapse of the Soviet era. This spirit continues to the present day. Professor Ümit Unluata, Director of Erdemli Institute of Marine Sciences (Middle East Technical University, Ankara) was of paramount importance in organising and fostering the work undertaken. We would like to devote this monograph to the memory of him, who died so prematurely. We are also grateful to Academician Professor V. N. Eremeev, Director of the Sevastopol Institute of Biology of the Southern Sea (National Academy of Sciences of Ukraine), and to the directors of Erdemli Institute of Marine Sciences (Professor Ilkay Salihoglu, Professor Sukru Besiktepe and Professor Ferit Bingel) who also made significant contributions to the Ukrainian–Turkish collaboration. We are grateful to Dr Bill Parr from the Black Sea Ecosystem Recovery Project for his valuable efforts in improving earlier drafts. All these investigations were carried out within the framework of the following five NATO linkage-grants: • Pelagic animal food supply in the unstable Black Sea environment, • Will the new alien ctenophore Beroe ovata control the plankton community in the Black Sea? • Grazing, growth and production of Calanus euxinus in the Black Sea, • Bioindicators for assessment of Black Sea ecosystem recovery, • Adaptability and vulnerability of marine species in changing environments. And four TUBITAK - NASU joint projects: • Quantification of the recent ctenophore invader Beroe ovata impact in the Black Sea • Monitoring of the Black Sea anchovy and sprat, • Salinity tolerance as a key factor of invasion success of the copepods of Calanus genus into the Sea of Marmara, • Salinity tolerance as a key factor of invasion success of the mesozooplankton species into the Sea of Marmara. We hope that this publication will make a substantial contribution to future studies of the Black Sea ecosystem and offers further understanding of those features regulating biological processes in this unique marine basin

Null-Result Detection and Einstein-Podolsky-Rosen (EPR) Correlations

It follows from Bell's theorem and quantum mechanics that the detection of a particle of an entangled pair can (somehow) "force" the other distant particle of the pair into a well-defined state (which is equivalente to a reduction of the state vector): no property previously shared by the particles can explain the predicted correlations. This result has been corroborated by experiment. However, it has not been experimantally proved-and it is far from obvious-that the absence of detection, as in null-result (NR) experiments could have the very same effect. In this paper a way to try to bridge this gap is suggested. As already shown for the case of EPR correlations, if NR detections cannot induce a reduction of the state vector, then faster-than-light (FTL) communication becomes possible, at least in pr\'inciple. But it will be demonstrated that-as entertained by Bohm-this does not necessarily lead to a causal paradox, or to the rejection of the Lorentz transformations.Comment: 16 pages, 1 figure. Similar to the version published in Foundations of Physics with an appendix on superluminal signalling without causal paradox include

Enhancing methane production from lignocellulosic biomass by combined steam‑explosion pretreatment and bioaugmentation with cellulolytic bacterium Caldicellulosiruptor bescii

Background: Biogas production from lignocellulosic biomass is generally considered to be challenging due to the recalcitrant nature of this biomass. In this study, the recalcitrance of birch was reduced by applying steam-explosion (SE) pretreatment (210 °C and 10 min). Moreover, bioaugmentation with the cellulolytic bacterium Caldicellulosiruptor bescii was applied to possibly enhance the methane production from steam-exploded birch in an anaerobic digestion (AD) process under thermophilic conditions (62 °C). Results: Overall, the combined SE and bioaugmentation enhanced the methane yield up to 140% compared to untreated birch, while SE alone contributed to the major share of methane enhancement by 118%. The best methane improvement of 140% on day 50 was observed in bottles fed with pretreated birch and bioaugmentation with lower dosages of C. bescii (2 and 5% of inoculum volume). The maximum methane production rate also increased from 4-mL CH4/ g VS (volatile solids)/day for untreated birch to 9-14-mL CH4/ g VS/day for steam-exploded birch with applied bioaugmentation. Bioaugmentation was particularly effective for increasing the initial methane production rate of the pretreated birch yielding 21-44% more methane than the pretreated birch without applied bioaugmentation. The extent of solubilization of the organic matter was increased by more than twofold when combined SE pretreatment and bioaugmentation was used in comparison with the methane production from untreated birch. The beneficial effects of SE and bioaugmentation on methane yield indicated that biomass recalcitrance and hydrolysis step are the limiting factors for efficient AD of lignocellulosic biomass. Microbial community analysis by 16S rRNA amplicon sequencing showed that the microbial community composition was altered by the pretreatment and bioaugmentation processes. Notably, the enhanced methane production by pretreatment and bioaugmentation was well correlated with the increase in abundance of key bacterial and archaeal communities, particularly the hydrolytic bacterium Caldicoprobacter, several members of syntrophic acetate oxidizing bacteria and the hydrogenotrophic Methanothermobacter. Conclusion: Our findings demonstrate the potential of combined SE and bioaugmentation for enhancing methane production from lignocellulosic biomass