86,593 research outputs found
A quantum non-Markovian collision model: incoherent swap case
No full textWe have recently presented a collision-model-based framework to tackle non-Markovian quantum dynamics (Ciccarello et al 2012 arXiv:1207.6554). As a distinctive feature, memory is introduced in a dynamical way by adding extra inter-ancillary collisions to a standard (memoryless) collision model. In this paper, we focus on the case where such intra-bath collisions are described by incoherent partial swap operations. After briefly reviewing the model, we show how to include temperature as an additional parameter by relaxing the assumption that each bath ancilla is initially in a pure state. We also calculate explicitly the dynamical map entailed by the master equation in the paradigmatic instance of a Jaynes-Cummings system-ancilla coupling
Resilience of singlet-state extraction against non-optimal resonance conditions
No full textWe have recently presented a protocol for extracting the singlet state of two non-interacting high-dimensional spins through post-selection of the internal state of interaction mediators sent in succession [F. Ciccarello et al., arXiv:0710.3855v1]. The scheme requires each mediator's wavevector to obey appropriate resonance conditions. Here we show the robustness of the scheme in the realistic case where such conditions are not sharply fulfilled
Non-Markovian dynamics from band edge effects and static disorder
No full textIt was recently shown [S. Lorenzo, F. Lombardo, F. Ciccarello and M. Palma, Sci. Rep. 7 (2017) 42729] that the presence of static disorder in a bosonic bath â whose normal modes thus become all Anderson-localized â leads to non-Markovianity in the emission of an atom weakly coupled to it (a process which in absence of disorder is fully Markovian). Here, we extend the above analysis beyond the weak-coupling regime for a finite-band bath so as to account for band edge effects. We study the interplay of these with static disorder in the emergence of non-Markovian behavior in terms of a suitable non-Markovianity measure
Interaction between hopping and static spins in a discrete network
No full textWe consider a process where a spin hops across a discrete network and at certain sites couples to static
spins. While this setting is implementable in various scenarios (e.g. quantum dots or coupled cavities)
the physics of such processes is still basically unknown. Here, we take a first step along this line by
scrutinizing a two-site and a three-site lattices, each with two static spins. Despite a generally complex
dynamics occurs, we show a regime such that the spin dynamics is described by an effective three-spin
chain. Tasks such as entanglement generation and quantum state transfer can be achieved accordingly
Resonant atom-field interaction in large-size coupled-cavity arrays
No full textWe consider an array of coupled cavitieswith staggered intercavity couplings,where each cavity mode interacts
with an atom. In contrast to large-size arrays with uniform hopping rates where the atomic dynamics is known
to be frozen in the strong-hopping regime, we show that resonant atom-field dynamics with significant energy
exchange can occur in the case of staggered hopping rates even in the thermodynamic limit. This effect arises
from the joint emergence of an energy gap in the free photonic dispersion relation and a discrete frequency at
the gap’s center. The latter corresponds to a bound normal mode stemming solely from the finiteness of the array
length. Depending on which cavity is excited, either the atomic dynamics is frozen or a Jaynes-Cummings-like
energy exchange is triggered between the bound photonic mode and its atomic analog. As these phenomena are
effective with any number of cavities, they are prone to be experimentally observed even in small-size arrays
Da Palermo a Madrid, tra scienza e censura. A proposito di alcuni libri della collezione del IV duca d'Uceda, viceré di Sicilia
No full textNel saggio si discute il caso di studio della ricca biblioteca privata del IV duca di Uceda e vicerè di Sicilia, Francisco Pacheco. L'analisi della collezione mostra il potenziale di circolazione di autori e libri sospetti di eresia tra Sicilia e Spagna alla fine del Seicento. Il lignaggio e la posizione politica di Uceda avevano permesso di fare omettere decine e decine di titoli dalla dichiarazione inventariale dovuta alla frontiera, senza incorrere in alcun controllo da parte degli agenti preposti. L'osservazione degli aspetti materiali della collezione Uceda, soprattutto la legatura, pregevole manifattura di maestranze operanti a Palermo, ha permesso di individuare molti più volumi di quelli descritti nell'inventario di Uceda. In questo modo, è stato possibile comprendere meglio le preferenze, le letture, gli interessi culturali e, in definitiva, la fisionomia intellettuale di un colto e raffinato governatore della Sicilia in piena età moderna.The essay discusses the case study of the rich private library of the 4th Duke of Uceda and viceroy of Sicily, Francisco Pacheco. The analysis of the collection shows the potential circulation of authors and books suspected of heresy, between Sicily and Spain, at the end of the seventeenth century. Uceda’s lineage and political position had allowed dozens and dozens of titles to be omitted from the inventory declaration due to the border, without incurring any control by the agents in charge. The observation of the material aspects of the Uceda collection, especially the binding, valuable craftsmanship of workers operating in Palermo, has allowed to identify many more volumes than those described in the inventory of Uceda. In this way, we are able to better understand the preferences, the readings, the cultural interests and, ultimately, the intellectual appearance of a cultured and refined governor of Sicily in the middle of the modern age
Waveguide-QED-based measurement of a reservoir spectral density
No full textThe spectral density (SD) function has a central role in the study of open quantum systems (OQSs). We discover a method allowing for a "static" measurement of the SD - i.e., it requires neither the OQS to be initially excited nor its time evolution tracked in time - which is not limited to the weak-coupling regime. This is achieved through one-dimensional photon scattering for a zero-temperature reservoir coupled to a two-level OQS via the rotating wave approximation. We find that the SD profile is a universal simple function of the photon's reflectance and transmittance. As such, it can be straightforwardly inferred from the photon's reflection and transmission spectra
Toward computability of trace distance discord
No full textIt is known that a reliable geometric quantifier of discord-like correlations can be built by employing the so-called trace distance, which is used to measure how far the state under investigation is from the closest 'classical-quantum' state. To date, the explicit calculation of this indicator for two qubits has only been accomplished for states where the reduced density matrix of the measured party is maximally mixed, a class that includes Bell-diagonal states. Here, we first reduce the required optimization for a general two-qubit state to the minimization of an explicit two-variable function. Using this framework, we show that the minimum can be analytically worked out in a number of relevant cases, including quantum-classical and X states. This provides an explicit and compact expression for the trace distance discord of an arbitrary state belonging to either of these important classes of density matrices
Atomic teleportation via cavity QED and position measurements: efficiency analysis
No full textWe have recently presented a novel protocol to teleport an unknown
atomic state via cavity QED and position measurements. Here, after a brief review
of our scheme, we provide a quantitative study of its efficiency. This is accomplished
by an explicit description of the measurement process that allows us to
derive the fidelity with respect to the atomic internal state to be teleporte
Biblioteche ecclesiastiche e società multiculturale: progettare i servizi
No full textIn this essay, multicultural library services are discussed in relation with the mission and the cultural role of ecclesiastical libraries in our multilingual society, within an international librarianship framework. Inclusion of all people, irrespective of their language and ethnic provenance, to the library services, is a key issue for libraries serving religious communities. Examples and definitions regarding the main IFLA standards on the subject are provided
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