Non-classical properties of quantum wave packets propagating in a Kerr-like medium

We investigate non-classical effects such as fractional revivals, squeezing and higher-order squeezing of photon-added coherent states propagating through a Kerr-like medium.The Wigner functions corresponding to these states at the instants of fractional revivals are obtained, and the extent of non-classicality quantified.Comment: 8 pages, 10 figure

Convex ordering and quantification of quantumness

The characterization of physical systems requires a comprehensive understanding of quantum effects. One aspect is a proper quantification of the strength of such quantum phenomena. Here, a general convex ordering of quantum states will be introduced which is based on the algebraic definition of classical states. This definition resolves the ambiguity of the quantumness quantification using topological distance measures. Classical operations on quantum states will be considered to further generalize the ordering prescription. Our technique can be used for a natural and unambiguous quantification of general quantum properties whose classical reference has a convex structure. We apply this method to typical scenarios in quantum optics and quantum information theory to study measures which are based on the fundamental quantum superposition principle.Comment: 9 pages, 2 figures, revised version; published in special issue "150 years of Margarita and Vladimir Man'ko

Adversarial Stacked Auto-Encoders for Fair Representation Learning

Training machine learning models with the only accuracy as a final goal may promote prejudices and discriminatory behaviors embedded in the data. One solution is to learn latent representations that fulfill specific fairness metrics. Different types of learning methods are employed to map data into the fair representational space. The main purpose is to learn a latent representation of data that scores well on a fairness metric while maintaining the usability for the downstream task. In this paper, we propose a new fair representation learning approach that leverages different levels of representation of data to tighten the fairness bounds of the learned representation. Our results show that stacking different auto-encoders and enforcing fairness at different latent spaces result in an improvement of fairness compared to other existing approaches.Comment: ICML2021 ML4data Workshop Pape

Creating and Verifying a Quantum Superposition in a Micro-optomechanical System

Micro-optomechanical systems are central to a number of recent proposals for realizing quantum mechanical effects in relatively massive systems. Here we focus on a particular class of experiments which aim to demonstrate massive quantum superpositions, although the obtained results should be generalizable to similar experiments. We analyze in detail the effects of finite temperature on the interpretation of the experiment, and obtain a lower bound on the degree of non-classicality of the cantilever. Although it is possible to measure the quantum decoherence time when starting from finite temperature, an unambiguous demonstration of a quantum superposition requires the mechanical resonator to be in or near the ground state. This can be achieved by optical cooling of the fundamental mode, which also provides a method to measure the mean phonon number in that mode. We also calculate the rate of environmentally induced decoherence and estimate the timescale for gravitational collapse mechanisms as proposed by Penrose and Diosi. In view of recent experimental advances, practical considerations for the realization of the described experiment are discussed.Comment: 19 pages, 8 figures, published in New J. Phys. 10 095020 (2008); minor revisions to improve clarity; fixed possibly corrupted figure

Nonclassical properties of states engineered by superpositions of quantum operations on classical states

We consider an experimentally realizable scheme for manipulating quantum states using a general superposition of products of field annihilation ($\hat{a}$) and creation ($\hat{a}^\dag$) operators of the type ($s \hat{a}\hat{a}^\dag+ t \hat{a}^\dag \hat{a}$), with $s^2 + t^2 = 1$. Such an operation, when applied on states with classical features, is shown to introduce strong nonclassicality. We quantify the generated degree of nonclassicality by the negative volume of Wigner distribution in the phase space and investigate two other observable nonclassical features, sub-Poissonian statistics and squeezing. We find that the operation introduces negativity in the Wigner distribution of an input coherent state and changes the Gaussianity of an input thermal state. This provides the possibility of engineering quantum states with specific nonclassical features.Comment: 19 pages, IOPclass(iopart.cls

Biogas production using water hyacinths to meet collective energy needs in a sahelian country

This paper presents a pilot project that investigates the possibility of producing biogas from a mixture of water hyacinth and fresh rumen residue – replacing firewood as a source of fuel – to meet the energy needs of a maternity facility in Niamey (Niger). The discontinuous-type installation (batch reactors) is made up of six digesters measuring 5 m3 each. The output during hot and cool seasons, 0.52 m3 and 0.29 m3 respectively of biogas per m3 of digester per day, has met the energy needs of the maternity facility, estimated at 8 m3 of biogas per day. The study revealed strong seasonal variations: output during the hot season is approximatively 1.8 times greater than it is during the cool season. Large quantities of water hyacinth, an invasive plant present in Niger since 1986, are manually harvested in aquatic environments. The project is run by a local NGO, the Groupe d’Initiative pour les Energies Renouvelables (GIER), and supported by UNICEF and the Niger Basin Authority. The duration of the project is 8 months.Ce papier présente un projet pilote vérifiant la possibilité de produire du biogaz à partir d’un mélange de jacinthe d’eau et de résidu frais de rumen, en substitution au bois de chauffe pour satisfaire aux besoins en énergie d’une maternité de Niamey (Niger). L’installation de type discontinu (réacteurs batch) est composée de six digesteurs de 5 m3. Les rendements en saison chaude et en saison fraîche, respectivement 0,52 et de 0,29 m3 de biogaz par m3 de digesteur par jour et ont permis de couvrir les besoins de la maternité évalués à 8 m3 de biogaz par jour. L’étude révèle une forte variation saisonnière : le rendement en saison chaude est d’environ 1,8 fois supérieur à celle de la saison fraîche. La jacinthe d’eau est une plante envahissante présente au Niger depuis 1986, dont des quantités importantes sont récoltées en  milieux aquatiques. Le projet est porté par une ONG locale, le Groupe d’Initiative pour les Energies Renouvelables (GIER) et est supporté par l’UNICEF et l’Autorité du Bassin du Niger. La durée du projet est fixée à huit mois.Presenta un proyecto piloto que investiga la posibilidad de producir biogás a partir de jacintos de agua y residuos ruminales frescos, que sustituyen a la madera como fuente de combustible, para cubrir las necesidades energéticas del hospital de maternidad de Niamey (Níger). La instalación activada en discontinuo (reactores secuenciales) está formada por seis digestores de 5 m3 cada uno. La producción durante las estaciones de calor y frío, 0,52 m3 y 0,29 m3 de biogás respectivamente por m3 de digestor al día, ha cubierto las necesidades energéticas del hospital de maternidad, que se calcula en 8 m3 de biogás al día. El estudio ha revelado importantes variaciones según la estación: la producción durante la estación de calor es aproximadamente 1,8 veces mayor que la cantidad producida durante la temporada de frío. En el medio acuático se cosechan manualmente grandes cantidades de jacinto, una planta invasiva presente en Níger desde 1986. El proyecto está dirigido por una ONG local, GIER, y apoyado por UNICEF y la Autoridad de Cuencas de Níger. El proyecto tiene una duración de 8 meses