Uncertainty, Monogamy, and Locking of Quantum Correlations

Squashed entanglement and entanglement of purification are quantum mechanical correlation measures and defined as certain minimisations of entropic quantities. We present the first non-trivial calculations of both quantities. Our results lead to the conclusion that both measures can drop by an arbitrary amount when only a single qubit of a local system is lost. This property is known as "locking" and has previously been observed for other correlation measures, such as the accessible information, entanglement cost and the logarithmic negativity. In the case of squashed entanglement, the results are obtained with the help of an inequality that can be understood as a quantum channel analogue of well-known entropic uncertainty relations. This inequality may prove a useful tool in quantum information theory. The regularised entanglement of purification is known to equal the entanglement needed to prepare a many copies of quantum state by local operations and a sublinear amount of communication. Here, monogamy of quantum entanglement (i.e., the impossibility of a system being maximally entangled with two others at the same time) leads to an exact calculation for all quantum states that are supported either on the symmetric or on the antisymmetric subspace of a dxd-dimensional system.Comment: 7 pages revtex4, no figures. v2 has improved presentation and a couple of references adde

Viscoelasticity and shear flow of concentrated, non-crystallizing colloidal suspensions: Comparison with Mode-Coupling Theory

We present a comprehensive rheological study of a suspension of thermosensitive particles dispersed in water. The volume fraction of these particles can be adjusted by the temperature of the system in a continuous fashion. Due to the finite polydispersity of the particles (standard deviation: 17%), crystallization is suppressed and no fluid-crystal transition intervenes. Hence, the moduli $G'$ and $G"$ in the linear viscoelastic regime as well as the flow curves (shear stress $\sigma(\dot{\gamma})$ as the function of the shear rate $\dot{\gamma}$) could be measured in the fluid region up to the vicinity of the glass transition. Moreover, flow curves could be obtained over a range of shear rates of 8 orders of magnitude while $G'$ and $G"$ could be measured spanning over 9 orders of magnitude. Special emphasis has been laid on precise measurements down to the smallest shear rates/frequencies. It is demonstrated that mode-coupling theory generalized in the integration through transients framework provides a full description of the flow curves as well as the viscoelastic behavior of concentrated suspensions with a single set of well-defined parameters

Limitations on Quantum Key Repeaters

A major application of quantum communication is the distribution of entangled particles for use in quantum key distribution (QKD). Due to noise in the communication line, QKD is in practice limited to a distance of a few hundred kilometres, and can only be extended to longer distances by use of a quantum repeater, a device which performs entanglement distillation and quantum teleportation. The existence of noisy entangled states that are undistillable but nevertheless useful for QKD raises the question of the feasibility of a quantum key repeater, which would work beyond the limits of entanglement distillation, hence possibly tolerating higher noise levels than existing protocols. Here we exhibit fundamental limits on such a device in the form of bounds on the rate at which it may extract secure key. As a consequence, we give examples of states suitable for QKD but unsuitable for the most general quantum key repeater protocol.Comment: 11+38 pages, 4 figures, Statements for exact p-bits weakened as non-locking bound on measured relative entropy distance contained an erro

Price-setting and price-adjustment behavior for fast-moving consumer goods

"In many economic models, it is assumed that prices adjust instantaneously to changes of economic conditions (e.g., to shocks in demand or production costs). Since the existence of price rigidities has been frequently documented, more realistic models require that infrequent and lumpy price adjustment have to be taken into account. There are still many unresolved issues in this area, both theoretically and empirically. In this paper, we show that the dynamics and dispersion of retail prices can be investigated using price data obtained from the GfK Consumer Panel for 1995. Our results document the importance of psychological pricing points for price setting, confirming results from many earlier studies. A new aspect of our analysis that has not been investigated in the literature is the relevance of psychological prices points for price adjustment and aggregation. We interpret our findings as suggestive evidence for the notion that rigidities are relevant for aggregate dynamics in Germany. However, we also confirm that a structural aggregation theory is necessary for a better understanding of the relevance of micro-level rigidities for aggregate dynamics. In such a more comprehensive model, price data obtained from the GfK Consumer Panel might also prove very helpful in the future. Among the three other areas of empirical research that could potentially be explored with price data from the GfK Consumer Panel, the analysis of the relationship between individual price dynamics, price dispersion and aggregate inflation proves particularly fruitful. Moreover, the very disaggregated, high-frequency data contained in this data-set are almost unique. In other research areas which require that prices changes (and not only distributions of prices) are observed over time, empirical tests unfortunately suffer from the fact that time series of individual prices can be constructed only under additional strong assumptions." (author's abstract

Geschäftsanalyse im Kontext der Unternehmensarchitektur

Zusammenfassung: Die Wandlungsfähigkeit von Organisationen ist ein wesentlicher Erfolgsfaktor, zu dem die Unternehmensarchitektur einen wichtigen Beitrag leisten kann. Geschäftsanalysen liefern die Voraussetzungen für das Verständnis und die transparente Weiterentwicklung des Geschäftsmodells und die dafür notwendige Ausrichtung der Informationstechnologie. Vor diesem Hintergrund wird am Beispiel eines Schweizerischen Versicherungsunternehmens gezeigt, wie durch Geschäftsanalyse einerseits das Verständnis des Geschäftsmodells gefördert und andererseits die Abstimmung zwischen Geschäfts- und IT-Architektur unterstützt wird. Ferner wird ein Ansatz vorgestellt, der verschiedene Ziele und Typen der Geschäftsanalyse im Kontext von Unternehmensarchitekturen zusammenführ

About:Kate – Media Literacy and Crossmedia Seriality

Zeitgenössische Fernsehserien mit ihren text-, kontext- und medienübergreifenden Erweiterungen bringen dynamisch vernetzte materiell-semiotische Erfahrungswelten hervor. Ihre konfliktreich artikulierte Eingebundenheit in alltägliche Lern- und Transformationsprozesse wird im Folgenden mit dem Blick auf performative, partizipative und interaktive Dimensionen populärer Medienkulturen diskutiert. Im Fokus stehen dabei Schnittstellen des intermediären und soziokulturellen Austauschs, die transitiven Dynamiken einer sich zunehmend global entfaltenden Serienkultur und die Spuren ihrer Transformation im Gebrauch. Diese werden am Beispiel der im Jahr 2013 im Auftrag des deutsch-französischen Senders Arte produzierten transmedialen Serie About:Kate veranschaulicht.Contemporary television series and their transtextual, -contextual and -media expansions produce dynamically networked material-semiotic environments of cultural experience. In what follows, their variously articulated involvement in everyday practice and learning will be discussed in terms of performativity, participation and interactivity. The focus is put on exploring series as transitive products and practices of today’s popular media culture, on traces of their increasingly global medial and socio-cultural circulation and transformation in use. In developing this position we analyze the pedagogical potential of the transmedia series About:Kate commissioned by the Franco-German TV-Network Arte in 2013

Entanglement of the Antisymmetric State

We analyse the entanglement of the antisymmetric state in dimension d × d and present two main results. First, we show that the amount of secrecy that can be extracted from the state is low, more precisely, the distillable key is bounded by $${O(\frac{1}{d})}$$ . Second, we show that the state is highly entangled in the sense that a large number of ebits are needed in order to create the state: entanglement cost is larger than a constant, independent of d. The second result is shown to imply that the regularised relative entropy with respect to separable states is also lower bounded by a constant. Finally, we note that the regularised relative entropy of entanglement is asymptotically continuous in the state. Elementary and advanced facts from the representation theory of the unitary group, including the concept of plethysm, play a central role in the proofs of the main result

Highly Entangled States With Almost No Secrecy

In this paper we illuminate the relation between entanglement and secrecy by providing the first example of a quantum state that is highly entangled, but from which, nevertheless, almost no secrecy can be extracted. More precisely, we provide two bounds on the bipartite entanglement of the totally antisymmetric state in dimension d x d. First, we show that the amount of secrecy that can be extracted from the state is low, to be precise it is bounded by O(1/d). Second, we show that the state is highly entangled in the sense that we need a large amount of singlets to create the state: entanglement cost is larger than a constant, independent of d. In order to obtain our results we use representation theory, linear programming and the entanglement measure known as squashed entanglement. Our findings also clarify the relation between the squashed entanglement and the relative entropy of entanglement.Comment: 5 pages, short version of arXiv:0910.415

Prediction of a double-antireflection coating made solely with SiN x in a single, directional deposition step

Silicon solar cell modules, where the EVA layer is replaced by an air gap, are able to produce the same electric power as standard modules with EVA only if their anti-reflective properties are enhanced. We propose a method to do this by exploiting the fact that, on Si surfaces textured with random pyramids, light incident from near normal angle always hits at least two pyramidal faces before being reflected back toward the sun. If these two faces are covered with an anti-reflective coating (ARC) made of one and the same material but with two different thicknesses, the coating acts as a double ARC. Such a coating can be produced by depositing the SiNx layer from an oblique angle, optimally from 14.7°. Our detailed raytracing analysis predicts that J sc can then be improved by 0.2 mA/cm2 for normal incident sunlight and AM1.5g standard illumination, and is improved for all angles within a cone with an apex angle of approximately 64°. Furthermore, the coating can be optimized for modules in vertical mounting, where a Jsc gain of 0.1 mA/cm2 is predicted for an angle of incidence of 40°

Unambiguous determination of spin dephasing times in ZnO

Time-resolved magneto-optics is a well-established optical pump probe technique to generate and to probe spin coherence in semiconductors. By this method, spin dephasing times T_2^* can easily be determined if their values are comparable to the available pump-probe-delays. If T_2^* exceeds the laser repetition time, however, resonant spin amplification (RSA) can equally be used to extract T_2^*. We demonstrate that in ZnO these techniques have several tripping hazards resulting in deceptive values for T_2^* and show how to avoid them. We show that the temperature dependence of the amplitude ratio of two separate spin species can easily be misinterpreted as a strongly temperature dependent T_2^* of a single spin ensemble, while the two spin species have T_2^* values which are nearly independent of temperature. Additionally, consecutive pump pulses can significantly diminish the spin polarization, which remains from previous pump pulses. While this barely affects T_2^* values extracted from delay line scans, it results in seemingly shorter T_2^* values in RSA.Comment: 11 pages, 10 figure