Search results for " Witness"
showing 10 items of 36 documents
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…
Uso della collaborazione processuale e dialogo fra magistrati nel contrasto al terrorismo e alla mafia
2020
The procedural provisions established in the fight against terrorism and the mafia and the characteristics of the investigations reveal common features. In high profile events, the criminal judge plays a strong and creative role, along with a peculiar structure of the charges, the recourse to maxi-investigations and maxi-trials which have permanently deformed the purpose of criminal procedure in a political- criminal function. Some investigators and prosecutors, dialoguing together, have strongly dominated the public debate and influenced the legislative evolution on the subject of procedural collaboration. The constant interaction is testified to by a common approach to the repentant, by t…
Scrivere è un trasmettere. La parola e l'abisso in Primo Levi
2019
The report proposes a reflection on writing in Levi, now understood as a "clear" practice of thought now, instead, as an expression of the irrational half of oneself, continually threatened by the abyss and by silence. Through a sampling of excerpts from poems, essays, interviews, novels, the complex relationship of the writer with the function of the word, liberating act, witnessing duty but also as a "dark" experience is shed light. Among the texts examined, those related to Paul Celan and his 'dark talk' allowed us to appreciate the ambiguous depth of the writing in Primo Levi.
L'esilio della testimonianza in Paul Celan
2019
The essay identifies a profound link between poem and witness, both as a voice of life that is violently erased, and as an invocation of the You who saves. The poetic vocation to the witness makes its way in Celan in contrast with a lucid look at the dramatic restriction of vital horizons and with a growing inclination to suicide. But his poetic path remains until the end of his life a transformation of the way towards death from a way of cancellation to a way that goes back to life "on its own margin"
Esclusione, parola, silenzio: Mariella Mehr
2019
The essay aims to present the poetic and narrative work of Mariella Mehr, an extraordinary witness of our time and one of the most significant poetic voices of contemporary German language literature. If the density of poetic language and the thematic choice bring Mehr clos- er to the very high examples of Celan, Sachs, Levi, the peculiar quality of writing, its rough perfection and the fiery temperature of the imagination make it unique in the prose of our time.
A colloquio con Gaspare Spatuzza. Un racconto di vita, una storia di stragi
2016
C’è un periodo della storia del nostro Paese che avremmo potuto raccontare come fosse il momento si sono aperte le porte dell’inferno. Questo sono state le stragi di mafia dei primi anni Novanta, con i lutti e le distruzioni provocate dall’attacco allo Stato da parte di Cosa Nostra e di altri poteri occulti. Si tratta di vicende narrate e indagate in tanti modi. La novità di questo studio è la strada, il percorso attraverso cui il lettore può esplorare la quotidianità di Cosa Nostra, quell’inferno dei vivi che – dopo aver tentato di fare guerra allo Stato – ancora oggi brucia vite umane, tiene sotto giogo interi quartieri, città, economie nazionali e internazionali. Il libro è il racconto d…