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Modeling quantum thermal machines provides a practical approach to describing the thermodynamic properties of quantum technologies and devices. For this purpose, power-law potentials are often employed as working mediums of quantum thermodynamic cycles to investigate the concepts of heat, work, and efficiency. With this in mind, we present the results for the Stirling and Otto numerical modeling of quantum thermal machines that use a general power law potential with a characteristic $q$ exponent. We calculate its energy spectra, showing that it recovers the traditional forms of harmonic oscillator and 1-D potential well. We derive expressions for the reduced energy exchanges during a complete cycle and for the efficiency/coefficient of performance as a function of the exponent $q$, the bath temperatures, and the frequency ratio. From these results, we identify parameters that yield desired properties, such as optimized performance and transitions between different operation modes. The findings highlight the role of power-like potentials in optimizing quantum heat engines and support the design of tailored engines with specific performance characteristics.

Quantum thermodynamics is a powerful theoretical tool for assessing the suitability of quantum materials as platforms for novel technologies. In particular, the modeling of quantum cycles allows us to investigate the heat changes and work extraction at the nanoscale, where quantum effects dominate over classical ones. In this Review, we cover the mathematical formulation used to model the quantum thermodynamic behavior of small-scale systems, building up the quantum analog versions of thermodynamic processes and reversible cycles. We discuss theoretical results obtained after applying this approach to model Heisenberg-like spin systems, which are toy models for metal complex systems. In addition, we discuss recent experimental advances in this class of materials that have been achieved using the quantum thermodynamic approach, paving the way for the development of quantum devices. Finally, we point out perspectives to guide future efforts in using quantum thermodynamics as a reliable and effective approach to establish metal complex systems as quantum materials for energy storage/harvesting purposes.

Quantum thermodynamics aims to explore quantum features to enhance energy conversion beyond classical limits. While significant progress has been made, the understanding of caloric potentials in quantum systems remains incomplete. In this context, this study focuses on deriving general expressions for these caloric potentials by developing a quantum Maxwell relationship obtained from a thermal average form of the Ehrenfest theorem. Our results recover the classical cases and also reveal that the isothermal entropy change can be related to genuine quantum correlations in the system. Thus, this work provides a comprehensive framework for understanding the caloric behavior of quantum systems and their potential applications in caloric devices.

Multispectral imagery is frequently incorporated into agricultural tasks, providing valuable support for applications such as image segmentation, crop monitoring, field robotics, and yield estimation. From an image segmentation perspective, multispectral cameras can provide rich spectral information, helping with noise reduction and feature extraction. As such, this paper concentrates on the use of fusion approaches to enhance the segmentation process in agricultural applications. More specifically, in this work, we compare different fusion approaches by combining RGB and NDVI as inputs for crop row detection, which can be useful in autonomous robots operating in the field. The inputs are used individually as well as combined at different times of the process (early and late fusion) to perform classical and DL-based semantic segmentation. In this study, two agriculture-related datasets are subjected to analysis using both deep learning (DL)-based and classical segmentation methodologies. The experiments reveal that classical segmentation methods, utilizing techniques such as edge detection and thresholding, can effectively compete with DL-based algorithms, particularly in tasks requiring precise foreground-background separation. This suggests that traditional methods retain their efficacy in certain specialized applications within the agricultural domain. Moreover, among the fusion strategies examined, late fusion emerges as the most robust approach, demonstrating superiority in adaptability and effectiveness across varying segmentation scenarios. The dataset and code is available at https://github.com/Cybonic/MISAgriculture.git., Comment: This preprint has been submitted to ROBOT23: Sixth Iberian Robotics Conference

This article describes a mean-field theoretical model for Spin-Crossover (SCO) materials and explores its implications. It is based on a simple Hamiltonian that yields the high spin molar fraction as a function of temperature and pressure, as well as a temperature-pressure phase diagram for the SCO transition. In order to test the model, we apply it to the giant Barocaloric Effect (BCE) of the SCO material [FeL$_2$][BF$_4$]$_2$ and comprehensively analyse its behavior. We found that optical phonons are responsible for 92\% of the total barocaloric entropy change. DFT calculations show that these optical phonons are mainly assigned to the low frequencies modes of vibration ($<400$ cm$^{-1}$), being associated to the Fe coordination., Comment: 6 figures

Low-dimensional metal complexes are versatile materials with tunable physical and chemical properties that make these systems promising platforms for caloric applications. In this context, this work proposes a quantum Stirling cycle based on a dinuclear metal complex as a working substance. The results show that the quantum cycle operational modes can be managed when considering the change in the magnetic coupling of the material and the temperature of the reservoirs. Moreover, magnetic susceptibility can be used to characterize the heat exchanges of each cycle step and, therefore, its performance. As a proof of concept, the efficiency of the heat engine is obtained from experimental susceptibility data. These results open doors for studying quantum thermodynamic cycles by using metal complexes; and further the development of emerging quantum technologies based on these advanced materials.

The urge for efficient and environmentally friendly alternatives for the current gas-based refrigeration is becoming more critical due to global warming and overpopulation. Among the main candidates, solid-state-based cooling technology is appealing to substitute the conventional systems. Recently, attention has been turned to the barocaloric effect in advanced materials, namely, plastic crystals and elastomers, with reports revealing great caloric responses around room temperature for a series of materials. In this sense, this review has the goal of collecting, organizing and comparing the results from the literature to provide an outlook on the subject.

We theoretically study the thermoelectric transport properties of strained HgTe in the topological insulator phase. We developed a model for the system using a Dirac Hamiltonian including the effect of strain induced by the interface between HgTe and the CdTe substrate. The conductivity tensor was explored assuming the electrons are scattered by charge impurities, while the thermopower tensor was addressed using the Mott relation. Seebeck and Nernst responses exhibit remarkable enhancements in comparison with other two-dimensional Dirac materials, such as graphene, germanane, prosphorene and stanene. The intensity of these termoeletric responses, their dependencies with the external perpendicular magnetic field and temperature are also addressed.

Quantum teleportation, which depends on entangled states, is a fascinating subject and an important branch of quantum information processing. The present work reports the use of a dipolar spin thermal system as a quantum channel to perform quantum teleportation. Non-locality, tested by violation of Bell's inequality and thermal entanglement, measured by negativity, unquestionably show that even entangled states that do not violate Bell's inequality can be useful for teleportation., Comment: 6 pages, 5 figures

Manganites have been attracted considerable attention due to some intriguing magnetic properties, such as magnetoresistance, spin glass behavior and superparamagnetism. In recent years, some studies point to the effect of particle size and dimensionality of these compounds in their magnetic features. Particularly, LaCaMnO material research is well explored concerning the bulk material. To overcome the lack of the information we successfully produced advanced nanostructures of La$_{0.6}$Ca$_{0.4}$MnO$_{3}$ manganites, namely nanotubes and nanoparticles by using a sol-gel modified method, to determine the size particle effect on the magnetism. The manganites crystal structure, magnetic and magnetocaloric properties were studied in a broad temperature range. Transmission electron microscopy revealed nanoparticles with sizes from 45 up to 223 nm, depending on the calcination temperature. It was found that the magnetic and magnetocaloric properties can be optimized by tuning the particle size; for instance, the magnetic transition broadening by decreasing the particle size. We report the relative cooling power (RCP) of these samples; it was found that the best RCP was observed for the 223 nm particle (508 J/Kg). Finally, this work contributes to the research on the magnetic properties and magnetocaloric potentials in nanostructured systems with distinct morphologies., Comment: 11 pages, 8 figures

The ratio of non-synonymous to synonymous substitutions $\omega(=d_{N}/d_{S})$ has been widely used as a measure of adaptive evolution in protein coding genes. Omega can be defined in terms of population genetics parameters as the fixation ratio of selected vs. neutral mutants. Here it is argued that approaches based on the infinite sites model are not appropriate to define $\omega$ for single codon locations. Simple models of amino acid substitution with reversible mutation and selection are analysed, and used to define $\omega$ under several evolutionary scenarios. In most practical cases $\omega<1$ when selection is constant throughout time. However, it is shown that when the pattern of selection on amino acids changes, for example after an environment shift, a temporary burst of adaptive evolution ($\omega\gg1$) can be observed. The fixation probability of a novel mutant under frequency dependent selection is calculated, and it is used to show why $\omega>1$ can be sometimes expected for single locations at equilibrium. An example with influenza data is discussed., Comment: 24 pages, 4 figures and 1 table. Manuscript written between January and April 2010