Macroscopic Entanglement and Phase Transitions

This paper summarises the results of our research on macroscopic entanglement in spin systems and free Bosonic gases. We explain how entanglement can be observed using entanglement witnesses which are themselves constructed within the framework of thermodynamics and thus macroscopic observables. These thermodynamical entanglement witnesses result in bounds on macroscopic parameters of the system, such as the temperature, the energy or the susceptibility, below which entanglement must be present. The derived bounds indicate a relationship between the occurrence of entanglement and the establishment of order, possibly resulting in phase transition phenomena. We give a short overview over the concepts developed in condensed matter physics to capture the characteristics of phase transitions in particular in terms of order and correlation functions. Finally we want to ask and speculate whether entanglement could be a generalised order concept by itself, relevant in (quantum induced) phase transitions such as BEC, and that taking this view may help us to understand the underlying process of high-T superconductivity.Comment: 9 pages, 7 figures (color), Submitted to special OSID issue, Proceedings of the 38th Symposium on Mathematical Physics - Quantum Entanglement & Geometry, Torun (Poland), June 200

Dynamical studies and product analysis of the reaction between O(1D) and H2/D2

In this work we study the dynamics of the O (1D) + H2/D2 reactions at fixed collision energies [4,5] using quasiclassical trajectories calculations on a double-valued potential energy surface for H2O [2]

Double-valued potential energy surface for H2O derived from accurate ab initio data and including long-range interactions

In a recent work we have been able to model the long-range interactions within the H2O molecule. Using these long-range energy terms, a complete potential energy surface has been obtained by fitting high-quality ab initio energies to a double-valued functional form in order to describe the crossing between the two lowest-potential-energy surfaces. The two diabatic surfaces are represented using the double many-body expansion model, and the crossing term is represented using a three-body energy function. To warrant a coherent and accurate description for all the dissociation channels we have refitted the potential energy functions for the H2(3Su 1), OH(2P), and OH(2S) diatomics. To represent the three-body extended Hartree–Fock nonelectrostatic energy terms, V1 , V2 , and V12 , we have chosen a polynomial on the symmetric coordinates times a range factor in a total of 148 coefficients. Although we have not used spectroscopic data in the fitting procedure, vibrational calculations, performed in this new surface using the DVR3D program suite, show a reasonable agreement with experimental data. We have also done a preliminary quasiclassical trajectory study ~300 K!. Our rate constant for the reaction O(1D)1H2(1Sg 1) !OH(2P)1H(2S), k(300 K)5(0.99960.024)310210 cm3 molecule21 s21, is very close to the most recent recommended value. This kinetic result reinforces the importance of the inclusion of the long-range forces when building potential energy surfaces

Witnessed Entanglement

We present a new measure of entanglement for mixed states. It can be approximately computable for every state and can be used to quantify all different types of multipartite entanglement. We show that it satisfies the usual properties of a good entanglement quantifier and derive relations between it and other entanglement measures.Comment: Revised version. 7 pages and one figur

The dynamics of the reaction between O (1D) and DH and the isotopic effect

In particular, we analyse the reactive cross section, the opacity function, and the differential cross sections. In this work we also study the energy distribution of the products for the O(1D) + DH reaction. We also analyse the H/D ratio, H/D, where there are larger divergences between the results from different potential energy surfaces and experiment. The agreement found between our QCT results [3,4,5] and experiment reinforces the accuracy of the H2O potential energy surface used.The reaction O(1D) + H2 OH + H and its isotopic variants plays an important role in atmospheric chemistry and also is important in combustion chemistry. It has been taken as a prototype for insertion reactions. As a result, it has been subject of several experimental studies. Also theoretical studies of its dynamics have been carried out

Controlling the stability of both the structure and velocity of domain walls in magnetic nanowires

For magnetic nanowire devices, the precise control of both domain wall (DW) motion and pinning behaviour is essential for reliable functional performance. The domain wall velocity and wall structure are typically sensitive to the driving field or spin-polarized current, and the pinning behaviour depends on the walls’ structure and chirality, leading to variability in behaviour. Here, a systematic study combining experimental measurements and micromagnetic simulations of planar nanowires with small fixed-angle structural modulations on both edges was undertaken to study the domain wall reversal regime. A phase diagram for the reversal field as a function of modulation amplitude was obtained that shows that three DW reversal regime. A range of field and modulation amplitudes were identified in which stable DW reversal occurs, where the wall velocity is constant as a function of field and the wall structure is stable, which is well suited to applications

Deep learning-based graffiti detection: A study using Images from the streets of Lisbon

This research work comes from a real problem from Lisbon City Council that was interested in developing a system that automatically detects in real-time illegal graffiti present throughout the city of Lisbon by using cars equipped with cameras. This system would allow a more efficient and faster identification and clean-up of the illegal graffiti constantly being produced, with a georeferenced position. We contribute also a city graffiti database to share among the scientific community. Images were provided and collected from different sources that included illegal graffiti, images with graffiti considered street art, and images without graffiti. A pipeline was then developed that, first, classifies the image with one of the following labels: illegal graffiti, street art, or no graffiti. Then, if it is illegal graffiti, another model was trained to detect the coordinates of graffiti on an image. Pre-processing, data augmentation, and transfer learning techniques were used to train the models. Regarding the classification model, an overall accuracy of 81.4% and F1-scores of 86%, 81%, and 66% were obtained for the classes of street art, illegal graffiti, and image without graffiti, respectively. As for the graffiti detection model, an Intersection over Union (IoU) of 70.3% was obtained for the test set.info:eu-repo/semantics/publishedVersio