Local unitary versus local Clifford equivalence of stabilizer states

We study the relation between local unitary (LU) equivalence and local Clifford (LC) equivalence of stabilizer states. We introduce a large subclass of stabilizer states, such that every two LU equivalent states in this class are necessarily LC equivalent. Together with earlier results, this shows that LC, LU and SLOCC equivalence are the same notions for this class of stabilizer states. Moreover, recognizing whether two given stabilizer states in the present subclass are locally equivalent only requires a polynomial number of operations in the number of qubits.Comment: 8 pages, replaced with published versio

ARGOS policy brief on semantic interoperability

Semantic interoperability requires the use of standards, not only for Electronic Health Record (EHR) data to be transferred and structurally mapped into a receiving repository, but also for the clinical content of the EHR to be interpreted in conformity with the original meanings intended by its authors. Accurate and complete clinical documentation, faithful to the patient’s situation, and interoperability between systems, require widespread and dependable access to published and maintained collections of coherent and quality-assured semantic resources, including models such as archetypes and templates that would (1) provide clinical context, (2) be mapped to interoperability standards for EHR data, (3) be linked to well specified, multi-lingual terminology value sets, and (4) be derived from high quality ontologies. Wide-scale engagement with professional bodies, globally, is needed to develop these clinical information standards

On the geometry of entangled states

The basic question that is addressed in this paper is finding the closest separable state for a given entangled state, measured with the Hilbert Schmidt distance. While this problem is in general very hard, we show that the following strongly related problem can be solved: find the Hilbert Schmidt distance of an entangled state to the set of all partially transposed states. We prove that this latter distance can be expressed as a function of the negative eigenvalues of the partial transpose of the entangled state, and show how it is related to the distance of a state to the set of positive partially transposed states (PPT-states). We illustrate this by calculating the closest biseparable state to the W-state, and give a simple and very general proof for the fact that the set of W-type states is not of measure zero. Next we show that all surfaces with states whose partial transposes have constant minimal negative eigenvalue are similar to the boundary of PPT states. We illustrate this with some examples on bipartite qubit states, where contours of constant negativity are plotted on two-dimensional intersections of the complete state space.Comment: submitted to Journal of Modern Optic

Sedimentkenmerken van strandzanden op de Belgische kust

The authors review the sedimentological characteristics of superficial beach sands using samples taken every 15 m along two transversal beach profiles separated by a distance of 1 km along the Belgian coast near Klemskerke. The westernmost spot (KP37) has been sampled four months after a beach nourishment with sands supplied from the Ravelingen bank situated at a few kilometers off Ostend. At the sampling time (31-1-'79) strong beach erosion attacked the youngest dunes near by the eastern station (KP 38). Granulometric characteristics and heavy-mineral characteristics (weight of heavy minerals in the sand fraction 63-2000µm, weight of heavy minerals in the different grades, heavy-mineral composition of the over-all sand fraction, length of the most occurring heavy minerals) of the beach sands as well as of the nourishment sands and of the youngest dune sands have been analysed. The results have been used to study the sedimentological variations in relation to the micromorphological position on the beach, the differences between both stations and the intluence of reworked Ravelingen sands and youngest dune sands upon the beach material. The three main sediment groups belong to different heavy-mineral associations. The youngest dune sands are similar to the H-group (BAAK), the nourishment sands of the Ravelingen to the beach sands south of Bergen (Holland coast) (EDELMAN-EISMA). The beach sands themselves show similarity to the Rhine-AS-Kreftenheye association (ZONNEVELD). This study of mineralogical and granulometrical characteristics offers interesting prospects of the identification of dune and beach sediments, of present day eolian sands and of some off-shore bank sands along the Belgian coast. It shows as well that these mineralogically different sediments may be used,if reworked, as natural tracers for the analyses of beach dynamics and sediment movements. The beach micromorphology commands greatly the sedimentological differences of the superficial beach sands. Especially the length of the heavy minerals proved to be an interesting argument. The heavy-mineral content varies greatly with the granulometric grade

A tale of two commons. Some preliminary hypotheses on the long-term development of the commons in Western and Eastern Europe, 11th-19th centuries

In this article, we present our hypotheses regarding the divergence in the development of common-property regimes between Eastern and Western Europe. The latter area developed formalized arrangements for the collective exploitation of natural resources particularly early, and it was chosen not only by farmers, but also in the cities – by craftsmen – to deal with the economic and social problems during the late medieval and early modern times. In the East the development of such institutions for collective action started – we believe – much later, due to a number of factors. Whereas in the West population growth and urbanization occurred together with a speedy commercialization of the economy, putting pressure on natural resources and hence leading to an increasing demand by peasants to formalize the collective use of their land, the peasants east of the Elbe River lacked the agency to demand such change in the governance regime of their land. They were limited in their behaviour by the strictures of the second serfdom, which was accompanied by lesser urbanization and commercialization. In this article, we offer some explanatory frameworks to understand and study this long-term development – or lack thereof – of institutions for collective action across the European continent