Search results for "witne"
showing 10 items of 83 documents
Scalable and effective multi-level entangled photon states: a promising tool to boost quantum technologies
2021
Abstract Multi-level (qudit) entangled photon states are a key resource for both fundamental physics and advanced applied science, as they can significantly boost the capabilities of novel technologies such as quantum communications, cryptography, sensing, metrology, and computing. The benefits of using photons for advanced applications draw on their unique properties: photons can propagate over long distances while preserving state coherence, and they possess multiple degrees of freedom (such as time and frequency) that allow scalable access to higher dimensional state encoding, all while maintaining low platform footprint and complexity. In the context of out-of-lab use, photon generation…
Dynamics of correlations due to a phase noisy laser
2012
We analyze the dynamics of various kinds of correlations present between two initially entangled independent qubits, each one subject to a local phase noisy laser. We give explicit expressions of the relevant quantifiers of correlations for the general case of single-qubit unital evolution, which includes the case of a phase noisy laser. Although the light field is treated as classical, we find that this model can describe revivals of quantum correlations. Two different dynamical regimes of decay of correlations occur, a Markovian one (exponential decay) and a non-Markovian one (oscillatory decay with revivals) depending on the values of system parameters. In particular, in the non-Markovia…
Quantumness and memory of one qubit in a dissipative cavity under classical control
2019
Hybrid quantum-classical systems constitute a promising architecture for useful control strategies of quantum systems by means of a classical device. Here we provide a comprehensive study of the dynamics of various manifestations of quantumness with memory effects, identified by non-Markovianity, for a qubit controlled by a classical field and embedded in a leaky cavity. We consider both Leggett-Garg inequality and quantum witness as experimentally-friendly indicators of quantumness, also studying the geometric phase of the evolved (noisy) quantum state. We show that, under resonant qubit-classical field interaction, a stronger coupling to the classical control leads to enhancement of quant…
Dynamics of entanglement in one-dimensional spin systems
2003
We study the dynamics of quantum correlations in a class of exactly solvable Ising-type models. We analyze in particular the time evolution of initial Bell states created in a fully polarized background and on the ground state. We find that the pairwise entanglement propagates with a velocity proportional to the reduced interaction for all the four Bell states. Singlet-like states are favored during the propagation, in the sense that triplet-like states change their character during the propagation under certain circumstances. Characteristic for the anisotropic models is the instantaneous creation of pairwise entanglement from a fully polarized state; furthermore, the propagation of pairwis…
BUILDING AN ENTANGLEMENT MEASURE ON PHYSICAL GROUND
2008
We introduce on physical grounds a new measure of multipartite entanglement for pure states. The function we define is discriminant and monotone under LOCC and moreover can be expressed in terms of observables of the system.
Hierarchy and dynamics of trace distance correlations
2013
We define and analyze measures of correlations for bipartite states based on trace distance. For Bell diagonal states of two qubits, in addition to the known expression for quantum correlations using this metric, we provide analytic expressions for the classical and total correlations. The ensuing hierarchy of correlations based on trace distance is compared to the ones based on relative entropy and Hilbert-Schmidt norm. Although some common features can be found, the trace distance measure is shown to differentiate from the others in that the closest uncorrelated state to a given bipartite quantum state is not given by the product of the marginals, and further, the total correlations are s…
Entanglement dynamics of two independent qubits in environments with and without memory
2007
A procedure to obtain the dynamics of $N$ independent qudits ($d$-level systems) each interacting with its own reservoir, for any arbitrary initial state, is presented. This is then applied to study the dynamics of the entanglement of two qubits, initially in an extended Werner-like mixed state with each of them in a zero temperature non-Markovian environment. The dependence of the entanglement dynamics on the purity and degree of entanglement of the initial states and on the amount of non-Markovianity is also given. This extends the previous work about non-Markovian effects on the two-qubit entanglement dynamics for initial Bell-like states [B. Bellomo \textit{et al.}, Phys. Rev. Lett. \te…
Chile helps Chile: exploring the effects of earthquake Chile 2010
2014
Purpose– The purpose of the present paper is to explore the political discourse present in the show Chile Ayuda a Chile [Chile helps Chile] to support the survivors and victims of the last earthquake hit Chile in 2010. Based on the belief that nationalism plays a vital role in cementing the process of recovery by making survivors believe that they, after all, have a new opportunity to be on feet again.Design/methodology/approach– The visual methodology (enrooted in the analysis of content) is the chosen technique to develop five indicators which replicates the nationalist sentiment of Chileans post-disaster context. The archetype of nationalism is activated whenever the community is in dang…
Vulnerability in health care - reflections on encounters in every day practice
2013
Vulnerability is a human condition and as such a constant human experience. However, patients and professional health care providers may be regarded as more vulnerable than people who do not suffer or witness suffering on a regular basis. Acquiring a deeper understanding of vulnerability would thus be of crucial importance for health care providers. This article takes as its point of departure Derek Sellman's and Havi Carel's discussion on vulnerability in this journal. Through different examples from the authors' research focusing on the interaction between health professionals and patients, existential, contextual, and relational dimensions of vulnerability are illuminated and discussed. …
Los medios masivos de comunicación y el terrorismo: entre la verdad y el miedo
2017
Los medios masivos de comunicación cumplen un rol importante en la sociedad, son una suerte de reforzadores morales que problematizan y ofrecen soluciones a las cuestiones importantes de la sociedad. No obstante, en la sociedad de consumo, somos testigos de un cambio sustancial en el rol de los medios quienes han pasado a ser productores del “espectáculo del desastre”. El 11 de septiembre ha marcado a fuego no solo el poder de los medios para distorsionar ciertas realidades a sus audiencias, sino para cubrir la noticia escondiendo las causas reales que fomentan el terrorismo. El presente ensayo intenta situarse como una critica constructiva al discurso periodístico y de los medios dominante…