Charger-mediated energy transfer in exactly-solvable models for quantum batteries

We present a systematic analysis and classification of several models of quantum batteries involving different combinations of two level systems and quantum harmonic oscillators. In particular, we study energy transfer processes from a given quantum system, termed charger, to another one, i.e. the proper battery. In this setting, we analyze different figures of merit, including the charging time, the maximum energy transfer, and the average charging power. The role of coupling Hamiltonians which do not preserve the number of local excitations in the charger-battery system is clarified by properly accounting them in the global energy balance of the model.Comment: 11 page

Charger-mediated energy transfer for quantum batteries: an open system approach

The energy charging of a quantum battery is analyzed in an open quantum setting, where the interaction between the battery element and the external power source is mediated by an ancilla system (the quantum charger) that acts as a controllable switch. Different implementations are analyzed putting emphasis on the interplay between coherent energy pumping mechanisms and thermalization

Quantum bath statistics tagging

The possibility of discriminating the statistics of a thermal bath using indirect measurements performed on quantum probes is presented. The scheme relies on the fact that, when weakly coupled with the environment of interest, the transient evolution of the probe toward its final thermal configuration, is strongly affected by the fermionic or bosonic nature of the bath excitations. Using figures of merit taken from quantum metrology such as the Holevo-Helstrom probability of error and the Quantum Chernoff bound, we discuss how to achieve the greatest precision in this statistics tagging procedure, analyzing different models of probes and different initial preparations and by optimizing over the time of exposure of the probe

Recovering complete positivity of non-Markovian quantum dynamics with Choi-proximity regularization

A relevant problem in the theory of open quantum systems is the lack of complete positivity of dynamical maps obtained after weak-coupling approximations, a famous example being the Redfield master equation. A number of approaches exist to recover well-defined evolutions under additional Markovian assumptions, but much less is known beyond this regime. Here we propose a numerical method to cure the complete-positivity violation issue while preserving the non-Markovian features of an arbitrary original dynamical map. The idea is to replace its unphysical Choi operator with its closest physical one, mimicking recent work on quantum process tomography. We also show that the regularized dynamics is more accurate in terms of reproducing the exact dynamics: this allows to heuristically push the utilization of these master equations in moderate coupling regimes, where the loss of positivity can have relevant impact.Comment: 12 pages, 5 figure

Going beyond Local and Global approaches for localized thermal dissipation

Identifying which master equation is preferable for the description of a multipartite open quantum system is not trivial and has led in the recent years to the local vs. global debate in the context of Markovian dissipation. We treat here a paradigmatic scenario in which the system is composed of two interacting harmonic oscillators A and B, with only A interacting with a thermal bath - collection of other harmonic oscillators - and we study the equilibration process of the system initially in the ground state with the bath finite temperature. We show that the completely positive version of the Redfield equation obtained using coarse-grain and an appropriate time-dependent convex mixture of the local and global solutions give rise to the most accurate semigroup approximations of the whole exact system dynamics, i.e. both at short and at long time scales, outperforming the local and global approaches

Chemical–physical characteristics, polyphenolic content and total antioxidant activity of three Italian-grown pomegranate cultivars

Background In Mediterranean countries, there is an increasing demand for pomegranate fruits due to their antioxidant properties and nutritional values. The large diffusion of new genotypes and cultivars requires the knowledge of all fruit characteristics in connection with the cultivation area, to satisfy the market demand. This study seeks to determine the fruit quality attributes and nutraceutical values of three pomegranate cultivars (Wonderful, Acco and Kamel) grown in the Mediterranean climate. Methods The fruits were evaluated for their main physico-chemical traits (weight, volume, height, width, thickness, total arils number, total arils weight, juiciness, fruit index, peel index and total soluble solids content/titratable acidity ratio), bioactive compounds (total phenolic content and total anthocyanin content) and antioxidant activities (radical scavenging activity and ferric reducing power). Results: The data showed that Acco fruit is bigger, juicier and sweeter when compared with the cultivars Wonderful and Kamel. Wonderful is the smallest, least juicy and least sweet but the reddest among all the studied cultivars. Regarding the phenolic compounds and antioxidant activity (radical scavenging activity and ferric reducing power), cultivar Wonderful has the highest values and cultivar Acco contains the most anthocyanin content. Conclusions This study showed that pomegranate cultivars grown in the Mediterranean area exhibit an appreciable quality, but there are significant differences in quality properties of the arils and juice

Portugal and Common Blond Oranges: are they the same Variety? Characteristics and Enhancement of the Oldest European Sweet Orange Variety

Background: Today, old citrus fruit varieties with traits suited to a market more attentive to a limited territorial distribution of certain species and the preservation of biodiversity are being promoted. One of these is the Portugal orange. The name 'Portugal' disappeared from the writings on citrus fruit growing in the first half of the last century, systematically replaced by the name 'Common Blond'. Methods: One hundred fruits of ‘Portugal’ and ‘Common Blond’ oranges come from two varietal collections found in Sicily. Physico-chemical and sensory analyses were carried out to evaluate the qualitative characteristics of both varieties and to confirm or confute the previous hypothesis. Results: These analyses confirm that from the point of view of fruit quality, there are no significant differences between 'Portugal' and 'Common Blond' oranges. The differences found can be attributed to the different growing environments, i.e. cultural practices, microclimate, fertilization, etc. Conclusion: Furthermore, the historical information provided also supports the hypothesis that the 'Portugal' orange simply changed its name to 'Common Blond', even though there were numerous bud variations that led to the selection of different clones

Tree and orchard variability of Silver King nectarine(Prunus persica (L.) Batsch) fruit quality components

The variability of crop quality accounts for most of seasonal variation of farmers’ incomes, since fruit growth and quality components may greatly change according to various environmental and within-tree factors. Canopy architecture and orchard layout are mainly responsible for fruit size, quality and its variability. A positive relationship was measured in peach between intercepted radiation and PAR and Trolox equivalent antioxidant capacity (TEAC). This study was carried out to measure within tree and orchard variability of fruit of the early ripening cv. Silver King nectarine (Prunus persica (L.), Batsch) 8-years-old peach trees trained to a Y-shape and Delayed vase. Fruit were picked twice and all harvested fruit were analysed in terms of size, soluble solids content, titratable acidity, pH, firmness and TEAC. Fruit weight variability between single trees was larger than within the tree and between training systems. Fruit soluble solid content and firmness had a higher variability than fruit size and within tree variability was higher in Delayed vase trees than in Y-shaped ones. TEAC changed with fruit position within the canopy