Synchronizing the dynamics of a single NV spin qubit on a parametrically coupled radio-frequency field through microwave dressing

A hybrid spin-oscillator system in parametric interaction is experimentally emulated using a single NV spin qubit immersed in a radio frequency (RF) field and probed with a quasi resonant microwave (MW) field. We report on the MW mediated locking of the NV spin dynamics onto the RF field, appearing when the MW driven Rabi precession frequency approaches the RF frequency and for sufficiently large RF amplitudes. These signatures are analog to a phononic Mollow triplet in the MW rotating frame for the parametric interaction and promise to have impact in spin-dependent force detection strategies

Coherent spin control at the quantum level in an ensemble-based optical memory

Long-lived quantum memories are essential components of a long-standing goal of remote distribution of entanglement in quantum networks. These can be realized by storing the quantum states of light as single-spin excitations in atomic ensembles. However, spin states are often subjected to different dephasing processes that limit the storage time, which in principle could be overcome using spin-echo techniques. Theoretical studies have suggested this to be challenging due to unavoidable spontaneous emission noise in ensemble-based quantum memories. Here we demonstrate spin-echo manipulation of a mean spin excitation of 1 in a large solid-state ensemble, generated through storage of a weak optical pulse. After a storage time of about 1 ms we optically read out the spin excitation with a high signal-to-noise ratio. Our results pave the way for long-duration optical quantum storage using spin-echo techniques for any ensemble-based memory.Comment: 5 pages, 2 figures, 1 tabl

\u3ci\u3eHistory of the Afghans \u3c/i\u3e

Translation from the original unpublished French manuscript by Captain William Jesse. History of Afghanistan

Towards highly multimode optical quantum memory for quantum repeaters

Long-distance quantum communication through optical fibers is currently limited to a few hundreds of kilometres due to fiber losses. Quantum repeaters could extend this limit to continental distances. Most approaches to quantum repeaters require highly multimode quantum memories in order to reach high communication rates. The atomic frequency comb memory scheme can in principle achieve high temporal multimode storage, without sacrificing memory efficiency. However, previous demonstrations have been hampered by the difficulty of creating high-resolution atomic combs, which reduces the efficiency for multimode storage. In this article we present a comb preparation method that allows one to increase the multimode capacity for a fixed memory bandwidth. We apply the method to a $^{151}$Eu$^{3+}$-doped Y$_2$SiO$_5$ crystal, in which we demonstrate storage of 100 modes for 51 $\mu$s using the AFC echo scheme (a delay-line memory), and storage of 50 modes for 0.541 ms using the AFC spin-wave memory (an on-demand memory). We also briefly discuss the ultimate multimode limit imposed by the optical decoherence rate, for a fixed memory bandwidth.Comment: 10 pages, 8 figure

Une resolution "historique" du Conseil de Securité

El autor analiza la resolución 1973 del Consejo de Seguridad de las Naciones Unidas sobre la cuestión de Libia, poniendo en evidencia las hipocresías de las "Grandes Potencias" y también de los nuevos paises llamados emergentes. Además, trata de desentrañar que significa realmente la apelación a la "governanza" en las relaciones internacionales contemporáneas, teniendo presente que las denominaciones tienen siempre un valor muy relativo tanto en la política como en el derecho internacional. Finalmente, se interroga sobre las consecuencias que tendrá esta "nueva ola de democratización" en los paises árabes.The author analyzes the 1973 resolution of the United Nations Security Council on the Libya matter, exposing the hypocrisy of the "Great Powers" and of the new so-colled emerging countries. The author also tries to discover what the call for "governance" in contemporary international relations really means, bearing in mind that denominations hove extreemely relative values both in polltics and in internationallaw. Finally, the author considers the possible consequences of this "new wove of democratization" in Arab countries.Sección Estudios.Instituto de Relaciones Internacionales (IRI

A Bayesian approach for uncertainty quantification in elliptic Cauchy problem

International audienceWe study the Cauchy problem in the framework of static linear elasticity and its resolution via the Steklov-Poincaré approach. In the linear Gaussian framework, the straightforward application of Bayes theory leads to formulas allowing to deduce the uncertainty on the identified field from the noise level. We use a truncated Ritz decomposition of the Steklov-Poincaré operator, which reduces the number of degrees of freedom and significantly lowers the computational cost

Reflexions sur la violence

Qu’on ne s’y trompe pas : si le titre a été emprunté à Georges Sorel, l’un des fondateurs de l’anarcho-syndicalisme et le théoricien de la violence entre le prolétariat et la bourgeoisie, le propos est tout autre, puisqu’il concerne l’utilisation de la violence armée dans la société internationale actuelleInstituto de Relaciones Internacionale

La Gouvernance mondiale et le Liban a l'epreuve l'une de l'autre

Née alors que la cassure du monde entre deux «blocs» essentiellement antagonistes s’estompait, la gouvernance mondiale posait dès l’origine une question fondamentale; elle se définissait, en effet, par axiologie et non par ontologie. En quittant la France, où il signifiait á peu près «gouvernement», et où il définissait naguère des institutions chargées de faire et de faire appliquer la loi, le mot avait pris, outre-Manche, une coloration nouvelle, institutionnelle, permettant de qualifier l’exercice de ses pouvoirs par les organes du gouvernement, puis, outre-Atlantique, un aspect plus fonctionnel et plus économique: la corporate governance désigne la capacité des dirigeants d’une entreprise de remplir leur mission première, faire de l’argent au profit des actionnaires. Les Latino-américains sont allés encore plus loin, en se passionnant pour la gobernabilidad, ou recherche des conditions qui permettront d’obtenir la gouvernance. (Párrafo extraído del texto a modo de resumen)Instituto de Relaciones Internacionales (IRI

Algunas consideraciones sobre la moralización de las Relaciones Internacionales.

En españolEl autor reflexiona sobre la moralización de las relaciones internacionales contemporáneas. Teniendo en cuenta dos temas de la agenda internacional: la "gouvernance" y el derecho penal internacional. La "gouvernance" ha devenido, según Ferrier, en una regla de las relaciones internacionales y en casi una norma de derecho internacional público. Esta temática está siempre presente en los debates de la ONU y de la Unión Europea. En lo referente al derecho penal internacional, señala sus dificultades para materializarse en una sociedad internacional hipócrita.En inglésThe author reflects upon ethicalisation of contemporary international relations, bearing in mind two items in the international agenda: "gouvernance" and international criminal law. "Gouvernance" has become, according to Ferrier, a rule in international relations and nearly a norm of public international law. The matter is always present in UN and EU discussions. As regards international criminal law, Ferrier points at its difficulties to materialise, in a hypocritical international society