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

Downsizing implementation and financial performance

In the present study we explore the relationship between downsizing decisions and corporate financial performance after top management has decided to downsize. Our focus is on the financial consequences arising from the amount of downsizing and the use of disengagement incentives. For this purpose, we use a sample of downsizing announcements in the Spanish press from 1995 up to 2001. Although the results show that the amount of downsizing is not significantly related to post-downsizing profitability, the evidence provided supports the finding that the use of disengagement incentives (which motivate workers to leave the organization) is negatively related to firm performance. Our analysis helps to understand the role that strategic downsizing decisions play in explaining observed variance in the performance of downsized firms. Thus, it advances scholarly organizational research by reinforcing the concept that corporate performance is not only contingent on strategies, but also influenced by the means through which these strategies are implemented

Does downsizing improve organizational performance? An analysis of Spanish manufacturing firms

The objective of this study is to examine the effect of downsizing on corporate performance, considering a sample of manufacturing firms drawn from the Spanish Survey of Business Strategies during the 1993- 2005 period. No significant differences in post-downsizing performance arise between companies which downsize and those that do not. Likewise, we find that substantial workforce reductions through collective dismissals do not either lead to improved performance levels. Downsizing, therefore, may not be a way for managers to increase performance, particularly in a context like the Spanish one, where the labour market is characterized by a high protection of employees’ rights and substantial contract termination costs

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

Almost separating and almost secure frameproof codes over q-ary alphabets

The final publication is available at Springer via http://dx.doi.org/10.1007/s10623-015-0060-zIn this paper we discuss some variations of the notion of separating code for alphabets of arbitrary size. We show how the original definition can be relaxed in two different ways, namely almost separating and almost secure frameproof codes, yielding two different concepts. The new definitions enable us to obtain codes of higher rate, at the expense of satisfying the separating property partially. These new definitions become useful when complete separation is only required with high probability, rather than unconditionally. We also show how the codes proposed can be used to improve the rate of existing constructions of families of fingerprinting codes.Peer ReviewedPostprint (author's final draft

Recursive linear estimation for discrete time systems in the presence of different multiplicative observation noises

This paper describes a design for a least mean square error estimator in discrete time systems where the components of the state vector, in measurement equation, are corrupted by different multiplicative noises in addition to observation noise. We show how known results can be considered a particular case of the algorithm stated in this paperState estimation, multiplicative noise, uncertain observations

Glory revealed in disk-integrated photometry of Venus

Context. Reflected light from a spatially unresolved planet yields unique insight into the overall optical properties of the planet cover. Glories are optical phenomena caused by light that is backscattered within spherical droplets following a narrow distribution of sizes; they are well known on Earth as localised features above liquid clouds. Aims. Here we report the first evidence for a glory in the disk-integrated photometry of Venus and, in turn, of any planet. Methods. We used previously published phase curves of the planet that were reproduced over the full range of phase angles with model predictions based on a realistic description of the Venus atmosphere. We assumed that the optical properties of the planet as a whole can be described by a uniform and stable cloud cover, an assumption that agrees well with observational evidence. Results. We specifically show that the measured phase curves mimic the scattering properties of the Venus upper-cloud micron-sized aerosols, also at the small phase angles at which the glory occurs, and that the glory contrast is consistent with what is expected after multiple scattering of photons. In the optical, the planet appears to be brighter at phase angles of 11-13 deg than at full illumination; it undergoes a maximum dimming of up to 10 percent at phases in between. Conclusions. Glories might potentially indicate spherical droplets and, thus, extant liquid clouds in the atmospheres of exoplanets. A prospective detection will require exquisite photometry at the small planet-star separations of the glory phase angles.Comment: In press. Astronomy & Astrophysics. Letter to the Editor; 201

Romhacking : localización de videojuegos clásicos en un contexto de aficionados

L'objectiu d'aquest article és presentar a la comunitat acadèmica el concepte de romhacking i descriure la metodologia seguida pels romhackers per localitzar videojocs clàssics. També presenta una reflexió sobre la tasca que duen a terme els romhackers.Este artículo tiene como objetivo presentar a la comunidad académica el concepto de romhacking y describir la metodología seguida por los romhackers para localizar videojuegos clásicos. Asimismo, se presenta una reflexión acerca de la tarea que llevan a cabo los romhackers.This paper aims at presenting to the academic community the concept of romhacking and the methodology followed by romhackers to localize classic video games. Furthermore, it presents a reflection on the work carried out by romhackers