Non-equilibrium quantum transport coefficients and the transient dynamics of full counting statistics in the strong coupling and non-Markovian regimes

Non-equilibrium transport properties of quantum systems have recently become experimentally accessible in a number of platforms in so-called full-counting experiments that measure transient and steady state non-equilibrium transport dynamics. We show that the effect of the measurement back-action can be exploited to gain access to relevant transport coefficients. This relationship is general, but becomes most conspicuous in the transient dynamics of open quantum systems understrong coupling to non-Markovian environments. In order to explore this regime, a new simulation method for the generation of full counting statistics of non-Markovian, strong-coupling transport settings has been developed that is expressed in terms of a hierarchy of equations of motion. With this tool we gain access to the relevant regime and instantiate our proposal with the study of energetic conductance between two baths connected via a few level system.Comment: 7 pages, 3 figures; To appear in Phys. Rev.

Ressenya. Jornada sobre el control de la qualitat i la responsabilitat per la difusió de la informació del sector públic a Internet

Celebració de la Jornada sobre el control de la qualitat i la responsabilitat per la difusió de la informació del sector públic a Internet. Barcelona, 17 de novembre de 2006.</p

An electronic Maxwell demon in the coherent strong-coupling regime

We consider a feedback control loop rectifying particle transport through a single quantum dot that is coupled to two electronic leads. While monitoring the occupation of the dot, we apply conditional control operations by changing the tunneling rates between the dots and its reservoirs, which can be interpreted as the action of a Maxwell demon opening or closing a shutter. This can generate a current at equilibrium or even against a potential bias, producing electric power from information. While this interpretation is well-explored in the weak-coupling limit, we can address the strong-coupling regime with a fermionic reaction-coordinate mapping, which maps the system into a serial triple quantum dot coupled to two leads. There, we find that a continuous projective measurement of the central dot would lead to a complete suppression of electronic transport due to the quantum Zeno effect. In contrast, a microscopic model for the quantum point contact detector implements a weak measurement, which allows for closure of the control loop without inducing transport blockade. In the weak-coupling regime between the central dot and its leads, the energy flows associated with the feedback loop are negligible, and the information gained in the measurement induces a bound for the generated electric power. In contrast, in the strong coupling limit, the protocol may require more energy for opening and closing the shutter than electric power produced, such that the device is no longer information-dominated and can thus not be interpreted as a Maxwell demon.Comment: to appear in PRB, side-by-side with arXiv:1711.0891

Educar en valores, misión del profesor

En este artículo se reconoce la intrínseca dificultad que entraña educar en valores. Sin embargo, se trata de una misión irrenunciable porque una educación de calidad no puede consistir sólo en la transmisión de saberes, sino que debe orientarse también hacia la formación de personas capaces de afrontar los desafíos de la sociedad actual. Los profesores deben convertirse en mediadores y guías que orienten a los alumnos hacia el descubrimiento de sus valores de referencia y hacia el desarrollo de las capacidades que les permitan desenvolverse de forma autónoma en la escuela y en la vida. Sólo el aprendizaje mediado permite que los sujetos mejoren sus ejecuciones y actualicen su potencial de aprendizaje constantemente

Overcoming organic and nitrogen overload in thermophilic anaerobic digestion of pig slurry by coupling a microbial electrolysis cell

The combination of the anaerobic digestion (AD) process with a microbial electrolysis cell (MEC) coupled to an ammonia stripping unit as a post-treatment was assessed both in series operation, to improve the quality of the effluent, and in loop configuration recirculating the effluent, to increase the AD robustness. The MEC allowed maintaining the chemical oxygen demand removal of the whole system of 46 ± 5% despite the AD destabilization after doubling the organic and nitrogen loads, while recovering 40 ± 3% of ammonia. The AD-MEC system, in loop configuration, helped to recover the AD (55% increase in methane productivity) and attained a more stable and robust operation. The microbial population assessment revealed an enhancement of AD methanogenic archaea numbers and a shift in eubacterial population. The AD-MEC combined system is a promising strategy for stabilizing AD against organic and nitrogen overloads, while improving the quality of the effluent and recovering nutrients for their reutilization.Postprint (author's final draft