Squashing Models for Optical Measurements in Quantum Communication

Measurements with photodetectors necessarily need to be described in the infinite dimensional Fock space of one or several modes. For some measurements a model has been postulated which describes the full mode measurement as a composition of a mapping (squashing) of the signal into a small dimensional Hilbert space followed by a specified target measurement. We present a formalism to investigate whether a given measurement pair of mode and target measurements can be connected by a squashing model. We show that the measurements used in the BB84 protocol do allow a squashing description, although the six-state protocol does not. As a result, security proofs for the BB84 protocol can be based on the assumption that the eavesdropper forwards at most one photon, while the same does not hold for the six-state protocol.Comment: 4 pages, 2 figures. Fixed a typographical error. Replaced the six-state protocol counter-example. Conclusions of the paper are unchange

Editors\u27 Introduction

The editors give an introduction to the volume

Crew Motion and the Dynamic Environment of Spaceborne Experiments

Analytical study of crew motion on dynamic environment of orbiting laboratorie

Processing Succinct Matrices and Vectors

We study the complexity of algorithmic problems for matrices that are represented by multi-terminal decision diagrams (MTDD). These are a variant of ordered decision diagrams, where the terminal nodes are labeled with arbitrary elements of a semiring (instead of 0 and 1). A simple example shows that the product of two MTDD-represented matrices cannot be represented by an MTDD of polynomial size. To overcome this deficiency, we extended MTDDs to MTDD_+ by allowing componentwise symbolic addition of variables (of the same dimension) in rules. It is shown that accessing an entry, equality checking, matrix multiplication, and other basic matrix operations can be solved in polynomial time for MTDD_+-represented matrices. On the other hand, testing whether the determinant of a MTDD-represented matrix vanishes PSPACE$-complete, and the same problem is NP-complete for MTDD_+-represented diagonal matrices. Computing a specific entry in a product of MTDD-represented matrices is #P-complete.Comment: An extended abstract of this paper will appear in the Proceedings of CSR 201

Flipping quantum coins

Coin flipping is a cryptographic primitive in which two distrustful parties wish to generate a random bit in order to choose between two alternatives. This task is impossible to realize when it relies solely on the asynchronous exchange of classical bits: one dishonest player has complete control over the final outcome. It is only when coin flipping is supplemented with quantum communication that this problem can be alleviated, although partial bias remains. Unfortunately, practical systems are subject to loss of quantum data, which restores complete or nearly complete bias in previous protocols. We report herein on the first implementation of a quantum coin-flipping protocol that is impervious to loss. Moreover, in the presence of unavoidable experimental noise, we propose to use this protocol sequentially to implement many coin flips, which guarantees that a cheater unwillingly reveals asymptotically, through an increased error rate, how many outcomes have been fixed. Hence, we demonstrate for the first time the possibility of flipping coins in a realistic setting. Flipping quantum coins thereby joins quantum key distribution as one of the few currently practical applications of quantum communication. We anticipate our findings to be useful for various cryptographic protocols and other applications, such as an online casino, in which a possibly unlimited number of coin flips has to be performed and where each player is free to decide at any time whether to continue playing or not.Comment: 17 pages, 3 figure

Discovery and Characterization of the Cryptic Psi Subunit of the Pseudomonad DNA Replicase

We previously reconstituted a minimal DNA replicase from Pseudomonas aeruginosa consisting of α and ϵ (polymerase and editing nuclease), β (processivity factor), and the essential τ, δ, and δ′ components of the clamp loader complex (Jarvis, T., Beaudry, A., Bullard, J., Janjic, N., and McHenry, C. (2005) J. Biol. Chem. 280, 7890-7900). In Escherichia coli DNA polymerase III holoenzyme, χ and Ψ are tightly associated clamp loader accessory subunits. The addition of E. coli χΨ to the minimal P. aeruginosa replicase stimulated its activity, suggesting the existence of χ and Ψ counterparts in P. aeruginosa. The P. aeruginosa χ subunit was recognizable from sequence similarity, but Ψ was not. Here we report purification of an endogenous replication complex from P. aeruginosa. Identification of the components led to the discovery of the cryptic Ψ subunit, encoded by holD. P. aeruginosa χ and Ψ were co-expressed and purified as a 1:1 complex. P. aeruginosa χΨ increased the specific activity of τ3δδ′ 25-fold and enabled the holoenzyme to function under physiological salt conditions. A synergistic effect between χΨ and single-stranded DNA binding protein was observed. Sequence similarity to P. aeruginosa Ψ allowed us to identify Ψ subunits from several other Pseudomonads and to predict probable translational start sites for this protein family. This represents the first identification of a highly divergent branch of the Ψ family and confirms the existence of Ψ in several organisms in which Ψ was not identifiable based on sequence similarity alone

Media Reporting and Business Cycles: Empirical Evidence based on News Data

Recent literature suggests that news shocks could be an important driver of economic cycles. In this article, we use a direct measure of news sentiment derived from media reports. This allows us to examine whether innovations in the reporting tone correlate with changes in the assessment and expectations of the business situation as reported by firms in the German manufacturing sector. We fi nd that innovations in news reporting affect business expectations, even when conditioning on the current business situation and industrial production. The dynamics of the empirical model con rm theoretical predictions that news innovations affect real variables such as production via changes in expectations. Looking at individual sectors within manufacturing, we fi nd that macroeconomic news is at least as important for business expectations as sector-spefici c news. This is consistent with the existence of information complementarities across sectors

The Archaeology of 19th-Century Farmsteads: The Results of a Workshop Held at the 1997 Annual Meeting of the Council for Northeast Historical Archaeology

A workshop was held at the 1997 annual meeting of the Council for Northeast Historical Archaeology (CNEHA) to address the question What do we do with 19th-century farmsteads in the Northeast? The workshop involved several brainstorming sessions in which the participants examined topics and problems associated with current approaches to the archaeological investigation of farmstead sites. These brainstorming sessions examined questions such as: What is a 19th-century farmstead? What are the research and public values of these sites? Which sites should be examined? and How should these sites be investigated? The workshop ended with the development of an action agenda with recommendations on how we as a discipline, and CNEHA as an organization, should proceed with the research, interpretation, and preservation of these types of sites

Implementation of the LDA+U method using the full potential linearized augmented plane wave basis

We provide a straightforward and efficient procedure to combine LDA+U total energy functional with the full potential linearized augmented plane wave method. A detailed derivation of the LDA+U Kohn-Sham type equations is presented for the augmented plane wave basis set, and a simple ``second-variation'' based procedure for self-consistent LDA+U calculations is given. The method is applied to calculate electronic structure and magnetic properties of NiO and Gd. The magnetic moments and band eigenvalues obtained are in very good quantitative agreement with previous full potential LMTO calculations. We point out that LDA+U reduces the total d charge on Ni by 0.1 in NiO

Filling a blank on the map: 60 years of fisheries in Equatorial Guinea

Despite a scarcity of pertinent information, it has been possible to reconstruct time series of marine fisheries catches for Equatorial Guinea from 1950 to 2010 using per capita fish consumption and population numbers for small-scale fisheries, catch rates and number of vessels for industrial fisheries and discard rates to estimate the discarded bycatch. Small-scale fisheries, industrial large-scale fisheries, domestic and legal and illegal foreign fisheries and their discards are all included. Total catches were estimated at 2.7 million tonnes over the time period considered, of which 653 000 t were caught domestically compared to 187 000 t reported by FAO. This shows that fisheries have more importance for Equatorial Guinea's food security than the official data suggest. In contrast to what is suggested by official figures, fisheries were shown to be strongly impacted by civil and political unrest; notably, they declined overall because of civil and political conflicts, socio-demographic dynamics, and a growing role of the newly discovered oil resources, which directly and indirectly threaten the food security of the people of Equatorial Guinea