Degenerate parametric oscillation in quantum membrane optomechanics

The promise of innovative applications has triggered the development of many modern technologies capable of exploiting quantum effects. But in addition to future applications, such quantum technologies have already provided us with the possibility of accessing quantum-mechanical scenarios that seemed unreachable just a few decades ago. With this spirit, in this work we show that modern optomechanical setups are mature enough to implement one of the most elusive models in the field of open system dynamics: degenerate parametric oscillation. The possibility of implementing it in nonlinear optical resonators was the main motivation for introducing such model in the eighties, which rapidly became a paradigm for the study of dissipative phase transitions whose corresponding spontaneously broken symmetry is discrete. However, it was found that the intrinsic multimode nature of optical cavities makes it impossible to experimentally study the model all the way through its phase transition. In contrast, here we show that this long-awaited model can be implemented in the motion of a mechanical object dispersively coupled to the light contained in a cavity, when the latter is properly driven with multi-chromatic laser light. We focus on membranes as the mechanical element, showing that the main signatures of the degenerate parametric oscillation model can be studied in state-of-the-art setups, thus opening the possibility of studying spontaneous symmetry breaking and enhanced metrology in one of the cleanest dissipative phase transitions.Comment: We welcome comments, suggestions, and (constructive) criticis

Photon correlation spectroscopy as a witness for quantum coherence

The development of spectroscopic techniques able to detect and verify quantum coherence is a goal of increasing importance given the rapid progress of new quantum technologies, the advances in the field of quantum thermodynamics, and the emergence of new questions in chemistry and biology regarding the possible relevance of quantum coherence in biochemical processes. Ideally, these tools should be able to detect and verify the presence of quantum coherence in both the transient dynamics and the steady state of driven-dissipative systems, such as light-harvesting complexes driven by thermal photons in natural conditions. This requirement poses a challenge for standard laser spectroscopy methods. Here, we propose photon correlation measurements as a new tool to analyse quantum dynamics in molecular aggregates in driven-dissipative situations. We show that the photon correlation statistics on the light emitted by a molecular dimer model can signal the presence of coherent dynamics. Deviations from the counting statistics of independent emitters constitute a direct fingerprint of quantum coherence in the steady state. Furthermore, the analysis of frequency resolved photon correlations can signal the presence of coherent dynamics even in the absence of steady state coherence, providing direct spectroscopic access to the much sought-after site energies in molecular aggregates

Driade space: an agent based simulation model for the analysis of the firm demography and the localization patterns in urban areas

An agent based model of firm mobility is presented in which diverse types of firms decide their geographical localization in function of some spatial variables. Although as much the regional economy as the geography have studied in depth the rules of localization of the companies, many of the complex behaviors that are observed in the reality are still, in great measure, unexplained. The simulation based on agents constitutes a new approach to the problem, allowing to integrate in the models of economy regional aspects of great relevance that, for its high complexity, could not be included in the analysis more than in qualitative terms. In the Driade Space model the demography of firms is considered in a wide sense: number of firms, entries and exits, distribution of sizes as well as the spatial density of firms. The entry of new companies in each period depends on the evolution of the market. The number of these is function of the profitability observed in the sector in the previous period and the height of the entry barriers. The companies are rational and they act on the variables within their reach in function of their objectives and of the limited information they have on the evolution of the market and the behavior of their competitors. This way, the companies in the moment of their entrance decide the localization they expect that will be more profitable considering their own characteristics while in the successive periods they decide on their investments and their production. The costs of the companies are not fixed; they depend not only on the production level and on the price of the used productive factors but also on the price of the land. The derived economies of the initial decision of localization are also considered. The characteristics of the territory where the firms are located are not static but rather evolve depending on the applied policies, demographic variables and the localization of the companies. Although the exits of the companies depend mainly on their profitability, they are also affected by random aspects. When the companies exit the market they leave a free space that can be covered by other companies favoring this way new entries. The model presented allows showing the endogenous rules of firm localization as well as the effects in the medium and the long term of the public policies.

Enhanced two-photon emission from a dressed biexciton

Radiative two-photon cascades from biexcitons in semiconductor quantum dots under resonant two-photon excitation are promising candidates for the generation of photon pairs. In this work, we propose a scheme to obtain two-photon emission that allows to operate under very intense driving fields. This approach relies on the Purcell enhancement of two-photon virtual transitions between states of the biexciton dressed by the laser. The richness provided by the biexcitonic level structure allows to reach a variety of regimes, from antibunched and bunched photon pairs with polarization orthogonal to the driving field, to polarization entangled two-photon emission. This evidences that the general paradigm of two-photon emission from a ladder of dressed states can find interesting, particular implementations in a variety of systems

Enabling Practical IPsec authentication for the Internet

On the Move to Meaningful Internet Systems 2006: OTM 2006 Workshops (First International Workshop on Information Security (IS'06), OTM Federated Conferences and workshops). Montpellier, Oct,/Nov. 2006There is a strong consensus about the need for IPsec, although its use is not widespread for end-to-end communications. One of the main reasons for this is the difficulty for authenticating two end-hosts that do not share a secret or do not rely on a common Certification Authority. In this paper we propose a modification to IKE to use reverse DNS and DNSSEC (named DNSSEC-to-IKE) to provide end-to-end authentication to Internet hosts that do not share any secret, without requiring the deployment of a new infrastructure. We perform a comparative analysis in terms of requirements, provided security and performance with state-of-the-art IKE authentication methods and with a recent proposal for IPv6 based on CGA. We conclude that DNSSEC-to-IKE enables the use of IPsec in a broad range of scenarios in which it was not applicable, at the price of offering slightly less security and incurring in higher performance costs.Universidad de Montpellier IIPublicad

Broadband transverse susceptibility in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22

Producción CientíficaNoncollinear spin systems with magnetically induced ferroelectricity from changes in spiral magnetic ordering have attracted significant interest in recent research due to their remarkable magnetoelectric effects with promising applications. Single phase multiferroics are of great interest for these new multifunctional devices, being Y-type hexaferrites good candidates, and among them the ZnY compounds due to their ordered magnetic behaviour over room temperature. Polycrystalline Y type hexaferrites with composition Ba0.5Sr1.5Zn2Fe2O22 (BSZFO) were sintered in 1050 °C–1250 °C temperature range. Transverse susceptibility measurements carried out on these BSZFO samples in the temperature range 80–350 K with DC fields up to ± 5000 Oe reveal different behaviour depending on the sintering temperature. Sample sintered at 1250 °C is qualitatively different, suggesting a mixed Y and Z phase like CoY hexaferrites. Sintering at lower temperatures produce single phase Y-type, but the transverse susceptibility behaviour of the sample sintered at 1150 °C is shifted at temperatures 15 K higher. Regarding the DC field sweeps the observed behaviour is a peak that shifts to lower values with increasing temperature, and the samples corresponding to single Y phase exhibit several maxima and minima in the 250 K–330 K range at low DC applied field as a result of the magnetic field induced spin transitions in this compound.Ministerio de Ciencia, Innovación y Universidades; Agencia Estatal de Investigación with FEDER (MAT2016-80784-P

Intertemporal Choice of Fuzzy Soft Sets

This paper first merges two noteworthy aspects of choice. On the one hand, soft sets and fuzzy soft sets are popular models that have been largely applied to decision making problems, such as real estate valuation, medical diagnosis (glaucoma, prostate cancer, etc.), data mining, or international trade. They provide crisp or fuzzy parameterized descriptions of the universe of alternatives. On the other hand, in many decisions, costs and benefits occur at different points in time. This brings about intertemporal choices, which may involve an indefinitely large number of periods. However, the literature does not provide a model, let alone a solution, to the intertemporal problem when the alternatives are described by (fuzzy) parameterizations. In this paper, we propose a novel soft set inspired model that applies to the intertemporal framework, hence it fills an important gap in the development of fuzzy soft set theory. An algorithm allows the selection of the optimal option in intertemporal choice problems with an infinite time horizon. We illustrate its application with a numerical example involving alternative portfolios of projects that a public administration may undertake. This allows us to establish a pioneering intertemporal model of choice in the framework of extended fuzzy set theorie

Estrategias de recuperación de predios baldíos en la Ciudad de Toluca: prospectiva del ordenamiento urbano

This study contributes to a scarcely worked topic, the lack of regulations that regulate the recovery of vacant urban land in the city of Toluca. The foundations of urban planning, territorial ordering and the law made it possible not only to identify the complexity of the recovery of the ownership of unoccupied urban land, but also the lack of cohesion in urban matters of the different systems at the state and local level. The results show that the regulatory framework of urban land uses does not include strategies for the reintegration of urban gaps into the city's economy. What sharpens its abandonment, commercial speculation, fraudulent alienation and underutilization under the weakness of urban policy. The legislative gaps identified in the State of Mexico defined the normative nature of the capital gains exchange policy and the recovery strategies that are proposed, which are subject to a long process of discussion in the local congress according to the Constitution of the State from Mexico; and approval in the different spheres of government of the State of Mexico and in the city councils. The contribution of this research constitutes a viable initiative in the context of the New General Law of Human Settlements, Territorial Planning and Urban Development, which raises the need to update the municipal plans of urban development, incorporating strategies that guarantee urban innovation in the medium and long term. The exchange of capital gains policy should be considered as a proposal for public regulation of the problems and contradictions of vacant urban land. This policy instructs on the fiscal mechanisms to recover the value of the uncultivated land, provides intervention 10 instruments that will contribute to the containment of commercial speculation of the urban land and to mitigate the outbreaks of unhealthiness. The fiscal mechanisms of the exchange of capital gains policy respond not only to the phenomenon of vacant urban land in the city of Toluca, in its general nature have an impact on the regulation of the real estate processes of the State of Mexico and previous adjustment applicable to other entities from the country. The contribution of this research constitutes an innovative initiative in the context of the provisions of the New General Law of Human Settlements, Territorial Planning and Urban Development. The State of Mexico and all the federal entities have the challenge of adapting the guidelines to the particularities demanded by urban development. It represents the opportunity to reformulate soil regulation instruments to adapt them to a new order to optimize urban uses and functions. The municipal plans of urban development that derive require policies and strategies of medium and long term that guarantee the reinsertion of the urban uncultivated lands to the economic dynamics and contribute in the urban densification. Based on the results of this research, additions are proposed to the New General Law of Human Settlements, Territorial Planning and Urban Development, which make up the general support of the exchange policy of capital gains proposed for the recovery of vacant urban land. The analytical method was applied in the literature review, orders, plans and programs, and the inductive method through a reference list and a technical sheet to update the information of urban wastelands.Resumen Este estudio contribuye con un tema escasamente trabajado, la carencia de ordenamientos que regulen la recuperación de los predios urbanos baldíos en la ciudad de Toluca. Los fundamentos del urbanismo, el ordenamiento territorial y el derecho permitieron identificar no solo la complejidad de la recuperación de la propiedad de los predios urbanos baldíos, sino también la carencia de cohesión en materia urbana de los diversos ordenamientos en el ámbito estatal y local. Los resultados muestran que el marco regulatorio de los usos de suelo urbano no contempla estrategias de reinserción de los vacíos urbanos a la economía de la ciudad. Lo que agudiza su abandono, la especulación comercial, la enajenación fraudulenta y la subutilización al amparo de la debilidad de la política urbana. Los vacíos legislativos identificados en el Estado de México definieron la naturaleza normativa de la política de intercambio de plusvalías y las estrategias de recuperación que se proponen, mismas que están sujetas a un proceso largo de discusión en el congreso local de acuerdo a la Constitución del Estado de México; y aprobación en los diversos ámbitos de gobierno del Estado de México y en los ayuntamientos. El aporte de esta investigación se constituye en una iniciativa viable en el contexto de la Nueva Ley General de Asentamientos Humanos, Ordenamiento Territorial y Desarrollo Urbano, misma que plantea la necesidad de actualizar los planes municipales de desarrollo urbano, incorporando estrategias que garanticen la innovación urbana a mediano y largo plazo. La política de intercambio de plusvalías debe considerarse como propuesta de regulación pública de los problemas y contradicciones de los predios urbanos baldíos. Esta política instruye sobre los mecanismos fiscales para recuperar el valor de la renta de los baldíos, dota de instrumentos de intervención que coadyuvarán en la contención de la especulación comercial del suelo urbano y en la mitigación de los focos de insalubridad. Los mecanismos fiscales de la política de intercambio de plusvalías responden no solo al fenómeno de los predios urbanos baldíos en la ciudad de Toluca, en su carácter general tienen incidencia en la regulación de los procesos inmobiliarios del Estado de México y previa adecuación aplicables a otras entidades del país. El aporte de esta investigación constituye una iniciativa innovadora en el contexto de las disposiciones de la Nueva Ley General de Asentamientos Humanos, Ordenamiento Territorial y Desarrollo Urbano. El Estado de México y todas las entidades federativas tienen el reto de adaptar los lineamientos a las particularidades que demanda el desarrollo urbano. 9 Representa la oportunidad para reformular los instrumentos de regulación del suelo para adaptarlos a un nuevo orden para optimizar los usos y funciones urbanas. Los planes municipales de desarrollo urbano que se deriven requieren de políticas y estrategias de mediano y largo plazo que garanticen la reinserción de los predios urbanos baldíos a la dinámica económica y coadyuven en la densificación urbana. A partir de los resultados de esta investigación se proponen adiciones a la Nueva Ley General de Asentamientos Humanos, Ordenamiento Territorial y Desarrollo Urbano, las cuales conforman el sustento general de la política de intercambio de plusvalías que se propone para la recuperación de los predios urbanos baldíos. Se aplicó el método analítico en la revisión de literatura, ordenamientos, planes y programas, y el método inductivo mediante un listado de referencia y una ficha técnica para actualizar la información de los baldíos urbanos.CONACYT Universidad Autónoma del Estado de Méxic