A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime

We present and implement a non-destructive detection scheme for the transition probability readout of an optical lattice clock. The scheme relies on a differential heterodyne measurement of the dispersive properties of lattice-trapped atoms enhanced by a high finesse cavity. By design, this scheme offers a 1st order rejection of the technical noise sources, an enhanced signal-to-noise ratio, and an homogeneous atom-cavity coupling. We theoretically show that this scheme is optimal with respect to the photon shot noise limit. We experimentally realize this detection scheme in an operational strontium optical lattice clock. The resolution is on the order of a few atoms with a photon scattering rate low enough to keep the atoms trapped after detection. This scheme opens the door to various different interrogations protocols, which reduce the frequency instability, including atom recycling, zero-dead time clocks with a fast repetition rate, and sub quantum projection noise frequency stability

Renormalization and Quantum Scaling of Frenkel-Kontorova Models

We generalise the classical Transition by Breaking of Analyticity for the class of Frenkel-Kontorova models studied by Aubry and others to non-zero Planck's constant and temperature. This analysis is based on the study of a renormalization operator for the case of irrational mean spacing using Feynman's functional integral approach. We show how existing classical results extend to the quantum regime. In particular we extend MacKay's renormalization approach for the classical statistical mechanics to deduce scaling of low frequency effects and quantum effects. Our approach extends the phenomenon of hierarchical melting studied by Vallet, Schilling and Aubry to the quantum regime.Comment: 14 pages, 1 figure, submitted to J.Stat.Phy

Ground state wavefunction of the quantum Frenkel-Kontorova model

The wavefunction of an incommensurate ground state for a one-dimensional discrete sine-Gordon model -- the Frenkel-Kontorova (FK) model -- at zero temperature is calculated by the quantum Monte Carlo method. It is found that the ground state wavefunction crosses over from an extended state to a localized state when the coupling constant exceeds a certain critical value. So, although the quantum fluctuation has smeared out the breaking of analyticity transition as observed in the classical case, the remnant of this transition is still discernible in the quantum regime.Comment: 5 Europhys pages, 3 EPS figures, accepted for publication in Europhys. Letter

Demonstration of Bunch Triple Splitting in the CERN PS

A technique for splitting bunches into three has recently been proposed as an alternative to debunching-rebunching in a synchrotron[1]. The preservation of longitudinal emittance and the possibility of maintaining a gap in the bunch train are key features expected from this new process. A proof of principle has been established experimentally at the CERN PS in 1999. This showed that the nominal longitudinal characteristics of the proton beam for the LHC could be achieved at the exit of the PS with the help of triple splitting. The method is described and experimental results presented. Other possible applications are sketched

Using score differences for search result diversification

We investigate the application of a light-weight approach to result list clustering for the purposes of diversifying search results. We introduce a novel post-retrieval approach, which is independent of external information or even the full-text content of retrieved documents; only the retrieval score of a document is used. Our experiments show that this novel approach is bene cial to e ectiveness, albeit only on certain baseline systems. The fact that the method works indicates that the retrieval score is potentially exploitable in diversity

Influencia del contenido de OHAP y de gentamicina en la liberación del antibiótico a partir de composites de OHAP/PEMMA

El objetivo de este trabajo fue estudiar la influencia del contenido de hidroxiapatita (OHAp) y de sulfato de gentamicina (SG) en la velocidad de liberación de dicho antibiótico a partir de materiales compuestos por OHAp, polimetacrilato de metilo (PMMA) y polimetacrilato de etilo (PEMA). Para ello se prepararon muestras con diferente proporción de OHAp (30 y 40%) y de SG (5 y 10%). El estudio de liberación se llevó a cabo sumergiendo 3 muestras de cada grupo en SBF a 37°C, el medio fue renovado a diferentes intervalos de tiempo durante 70 días. La concentración de gentamicina fue determinada por el método del o-ftaldialdehído. Los resultados del estudio de liberación mostraron, que la liberación ocurre de manera más rápida durante las primeras 10 horas de inmersión en SBF y que posteriormente se hace más lenta. Se observó que las muestras con un mayor tanto por ciento (40%) de OHAp liberan mayor cantidad de antibiótico. Las muestras con un 40% de OHAp liberaron el 100% de SG a los 70 días, mientras que en ese mismo período las muestras con 30% de OHAp liberaron un 85%. Por otra parte, se observó que la cantidad de gentamicina añadida inicialmente no afecta el tanto por ciento de SG que se libera.Peer Reviewe

Self-tuning personalized information retrieval in an ontology-based framework

The final publication is available at Springer via http://dx.doi.org/10.1007/11575863_119Proceedings of OTM Confederated Internationl Workshops and Posters, AWeSOMe, CAMS, GADA, MIOS+INTEROP, ORM, PhDS, SeBGIS, SWWS, and WOSE 2005, Agia Napa, Cyprus, October 31 - November 4, 2005.Reliability is a well-known concern in the field of personalization technologies. We propose the extension of an ontology-based retrieval system with semantic-based personalization techniques, upon which automatic mechanisms are devised that dynamically gauge the degree of personalization, so as to benefit from adaptivity but yet reduce the risk of obtrusiveness and loss of user control. On the basis of a common domain ontology KB, the personalization framework represents, captures and exploits user preferences to bias search results towards personal user interests. Upon this, the intensity of personalization is automatically increased or decreased according to an assessment of the imprecision contained in user requests and system responses before personalization is applied.This research was supported by the European Commission under contract FP6- 001765 aceMedia. The expressed content is the view of the authors but not necessarily the view of the aceMedia project as a whole

Proposal for a Cavity Phase Observation System in the PS Machine

In multi-cavity synchrotrons it is essential to be able to measure the phase difference between RF cavities. Errors in relative phase can have a particularly deleterious effect on the beam during RF gymnastics. Currently, two methods are available to measure the relative phase in the CERN Proton Synchrotron (PS), but neither attains the desired resolution nor covers the full arsenal of cavities. This note describes a system that will measure the relative phase between cavities with high resolution. The system makes use of the digital hardware deployed in the LEIR beam control and of the corresponding DSP and FPGA signal processing. The focus is on beams controlled by the Multi Harmonic Source (MHS) clock. The system described here is also a step towards the deployment of a new generation of digital beam control systems for the PS Complex machines, within the framework of the LHC injector consolidation and following the successful commissioning of the LEIR digital beam control system. Some expected benefits are briefly summarised at the end of this documen

A two step algorithm for learning from unspecific reinforcement

We study a simple learning model based on the Hebb rule to cope with "delayed", unspecific reinforcement. In spite of the unspecific nature of the information-feedback, convergence to asymptotically perfect generalization is observed, with a rate depending, however, in a non- universal way on learning parameters. Asymptotic convergence can be as fast as that of Hebbian learning, but may be slower. Moreover, for a certain range of parameter settings, it depends on initial conditions whether the system can reach the regime of asymptotically perfect generalization, or rather approaches a stationary state of poor generalization.Comment: 13 pages LaTeX, 4 figures, note on biologically motivated stochastic variant of the algorithm adde

Beams in the CERN PS complex after the RF upgrades for LHC

In preparation for the Large Hadron Collider (LHC), extensive modifications have been made to the RF equipment of the PS Booster (PSB) and of the PS during the winter shut down 97-98. Low-frequency RF systems (0.6 - 1.8 MHz and 1.2 - 3.9 MHz) have been installed in the PSB and fixed frequency (40 and 80 MHz) systems in the PS. The longitudinal characteristics of all beams are changed to make the best use of the new capabilities. This paper summarises the characteristics of the new equipment and describes the RF gymnastics used to generate the various beams. The performances achieved so far ar e reported and compared to former results. Future plans are sketched