Moments of Shared Prayer: NCYC 2005

The National Catholic Youth Conference 2005 was held in Atlanta from October 27th to October 30th. A Programming Team, of which I was the director designed prayer for five major prayer sessions, which involved many youth leaders and 18,000 youth participants. Over the course of 5 months, I met with the Programming Team, a Technical Crew and the Sponsoring Organization, as well as several committees who had to approve the scripts. Prior to the conference, the Programming Team trained young animators into various leadership roles: singers, cantors, readers and movers. At the conference, it was my responsibility to see that the sessions were as close as possible, in reality, to what the teams had envisioned

The German stem cell network GSCN - a nationwide network with many tasks

The German Stem Cell Network (GSCN) aims at creating synergies between all areas of basic and applied stem cell research and to provide an interface between science, education, politics and society as a whole. The central task of the GSCN is to pool the expertise in stem cell research in Germany and develop synergies between basic research, regenerative medicine and pharmacology. The initiative promotes innovative research activities on a national and international level. In addition, targeted information and events are offered to encourage the public discourse on stem cell research. The objectives of the network are: To maintain an organizational structure for a German network for basic and applied stem cell research; To organize joint annual conferences on stem cell research to be rotated among German cities; To coordinate scientific and strategic working groups; To provide a platform for communication on stem cell research, enabling exchange of important news, discussions and networking between scientists, institutions, policy-makers and the general public (in German and English); To publish documents about basic and applied stem cell research in Germany and help to organize public meetings and outreach programs on these topics

Global Governance and the Limits of Health Security

The Ebola outbreak in West Africa has exposed the limits of the current approach to the global governance of infectious diseases, which mixes public health and security interests. International efforts to strengthen ‘health security’ quickly faltered when confronted with weak national health systems. Costly attempts by Western governments to strengthen global health security by developing new medical countermeasures, though important, did not yield a single, effective, widely available treatment or vaccine before the outbreak occurred. The World Health Organization (WHO), which had made strengthening global health security a strategic objective, was unable to marshal a rapid international response to the epidemic due to its institutional structure and recent cutbacks in its outbreak and emergency response department. In the end, governments could only try to get ‘ahead’ of the disease via a heavily militarised response that came too late for the thousands who have already died, that remains of uncertain sustainability, and that raises profound challenges for already stretched armed forces. The time has come to move from a focus on health security and international crisis response, to a system of global governance capable of addressing infectious disease outbreaks in an orderly, organised and sustainable manner.UK Department for International Developmen

Optical Quantum Computation with Perpetually Coupled Spins

The possibility of using strongly and continuously interacting spins for quantum computation has recently been discussed. Here we present a simple optical scheme that achieves this goal while avoiding the drawbacks of earlier proposals. We employ a third state, accessed by a classical laser field, to create an effective barrier to information transfer. The mechanism proves to be highly efficient both for continuous and pulsed laser modes; moreover it is very robust, tolerating high decay rates for the excited states. The approach is applicable to a broad range of systems, in particular dense structures such as solid state self-assembled (e.g., molecular) devices. Importantly, there are existing structures upon which `first step' experiments could be immediately performed.Comment: 5 pages including 3 figures. Updated to published versio

Elliptical orbits in the Bloch sphere

As is well known, when an SU(2) operation acts on a two-level system, its Bloch vector rotates without change of magnitude. Considering a system composed of two two-level systems, it is proven that for a class of nonlocal interactions of the two subsystems including \sigma_i\otimes\sigma_j (with i,j \in {x,y,z}) and the Heisenberg interaction, the geometric description of the motion is particularly simple: each of the two Bloch vectors follows an elliptical orbit within the Bloch sphere. The utility of this result is demonstrated in two applications, the first of which bears on quantum control via quantum interfaces. By employing nonunitary control operations, we extend the idea of controllability to a set of points which are not necessarily connected by unitary transformations. The second application shows how the orbit of the coherence vector can be used to assess the entangling power of Heisenberg exchange interaction.Comment: 9 pages, 4 figures, few corrections, J. Opt. B: Quantum Semiclass. Opt. 7 (2005) S1-S

Arithmetical Congruence Preservation: from Finite to Infinite

Various problems on integers lead to the class of congruence preserving functions on rings, i.e. functions verifying $a-b$ divides $f(a)-f(b)$ for all $a,b$. We characterized these classes of functions in terms of sums of rational polynomials (taking only integral values) and the function giving the least common multiple of $1,2,\ldots,k$. The tool used to obtain these characterizations is "lifting": if $\pi\colon X\to Y$ is a surjective morphism, and $f$ a function on $Y$ a lifting of $f$ is a function $F$ on $X$ such that $\pi\circ F=f\circ\pi$. In this paper we relate the finite and infinite notions by proving that the finite case can be lifted to the infinite one. For $p$-adic and profinite integers we get similar characterizations via lifting. We also prove that lattices of recognizable subsets of $Z$ are stable under inverse image by congruence preserving functions

Pattern formation in quantum Turing machines

We investigate the iteration of a sequence of local and pair unitary transformations, which can be interpreted to result from a Turing-head (pseudo-spin $S$) rotating along a closed Turing-tape ($M$ additional pseudo-spins). The dynamical evolution of the Bloch-vector of $S$, which can be decomposed into $2^{M}$ primitive pure state Turing-head trajectories, gives rise to fascinating geometrical patterns reflecting the entanglement between head and tape. These machines thus provide intuitive examples for quantum parallelism and, at the same time, means for local testing of quantum network dynamics.Comment: Accepted for publication in Phys.Rev.A, 3 figures, REVTEX fil

Driven Spin Systems as Quantum Thermodynamic Machines: Fundamental Limits

We show that coupled two level systems like qubits studied in quantum information can be used as a thermodynamic machine. At least three qubits or spins are necessary and arranged in a chain. The system is interfaced between two split baths and the working spin in the middle is externally driven. The machine performs Carnot-type cycles and is able to work as heat pump or engine depending on the temperature difference of the baths $\Delta T$ and the energy differences in the spin system $\Delta E$. It can be shown that the efficiency is a function of $\Delta T$ and $\Delta E$.Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev.

Tight lower bound to the geometric measure of quantum discord

Dakic, Vedral and Brukner [Physical Review Letters \tf{105},190502 (2010)] gave a geometric measure of quantum discord in a bipartite quantum state as the distance of the state from the closest classical quantum (or zero discord) state and derived an explicit formula for a two qubit state. Further, S.Luo and S.Fu [Physical Review A \tf{82}, 034302 (2010)] obtained a generic form of this geometric measure for a general bipartite state and established a lower bound. In this brief report we obtain a rigorous lower bound to the geometric measure of quantum discord in a general bipartite state which dominates that obtained by S.Luo and S.Fu.Comment: 10 pages,2 figures. In the previous versions, a constraint was ignored while optimizing the second term in Eq.(5), in which case, only a lower bound on the geometric discord can be obtained. The title is also consequently changed. Accepted in Phys.Rev.