Entropy production and information fluctuations along quantum trajectories

Employing the stochastic wave function method, we study quantum features of stochastic entropy production in nonequilibrium processes of open systems. It is demonstarted that continuous measurements on the environment introduce an additional, non-thermal contribution to the entropy flux, which is shown to be a direct consequence of quantum fluctuations. These features lead to a quantum definition of single trajectory entropy contributions, which accounts for the difference between classical and quantum trajectories and results in a quantum correction to the standard form of the integral fluctuation theorem.Comment: 9 pages, 5 figure

Spin-1/2 sub-dynamics nested in the quantum dynamics of two coupled qutrits

In this paper we investigate the quantum dynamics of two spin-1 systems, $\vec{\textbf{S}}_1$ and $\vec{\textbf{S}}_2$, adopting a generalized $(\vec{\textbf{S}}_1+\vec{\textbf{S}}_2)^2$-nonconserving Heisenberg model. We show that, due to its symmetry property, the nine-dimensional dynamics of the two qutrits exactly decouples into the direct sum of two sub-dynamics living in two orthogonal four- and five-dimensional subspaces. Such a reduction is further strengthened by our central result consisting in the fact that in the four-dimensional dynamically invariant subspace, the two qutrits quantum dynamics, with no approximations, is equivalent to that of two non interacting spin 1/2's. The interpretative advantages stemming from such a remarkable and non-intuitive nesting are systematically exploited and various intriguing features consequently emerging in the dynamics of the two qutrits are deeply scrutinised. The possibility of exploiting the dynamical reduction brought to light in this paper for exactly treating as well time-dependent versions of our Hamiltonian model is briefly discussed.Comment: 14 pages, 11 figures; Last two authors name corrected, corrected typos, Fig. 11 changed (same result

Distillation of Entanglement between Distant Systems by Repeated Measurements on Entanglement Mediator

A recently proposed purification method, in which the Zeno-like measurements of a subsystem can bring about a distillation of another subsystem in interaction with the former, is utilized to yield entangled states between distant systems. It is shown that the measurements of a two-level system locally interacting with other two spatially separated not coupled subsystems, can distill entangled states from the latter irrespectively of the initial states of the two subsystems.Comment: 11 pages, 2 figures; the version accepted for publication in Phys. Rev.

Bounds on the entanglement of two-qutrit systems from fixed marginals

We discuss the problem of characterizing upper bounds on entanglement in a bipartite quantum system when only the reduced density matrices (marginals) are known. In particular, starting from the known two-qubit case, we propose a family of candidates for maximally entangled mixed states with respect to fixed marginals for two qutrits. These states are extremal in the convex set of two-qutrit states with fixed marginals. Moreover, it is shown that they are always quasidistillable. As a by-product we prove that any maximally correlated state that is quasidistillable must be pure. Our observations for two qutrits are supported by numerical analysis

Non-conditioned generation of Schroedinger cat states in a cavity

We investigate the dynamics of a two-level atom in a cavity filled with a nonlinear medium. We show that the atom-field detuning $\delta$ and the nonlinear parameter $\chi^{(3)}$ may be combined to yield a periodic dynamics and allowing the generation of almost exact superpositions of coherent states ({\sl Schr\"odinger} cats). By analysing the atomic inversion and the field purity, we verify that any initial atom-field state is recovered at each revival time, and that a coherent field interacting with an excited atom evolves to a superposition of coherent states at each collapse time. We show that a mixed field state (statistical mixture of two coherent states) evolves towards a pure field state ({\sl Schr\"odinger} cat) as well. We discuss the validity of those results by using the field fidelity and the {\sl Wigner} function.Comment: REVTeX4, 8 pages, 7 figures, link to an external animation fil

Effect of Image Forces on Polyelectrolyte Adsorption at a Charged Surface

The adsorption of flexible and highly charged polyelectrolytes onto oppositely charged planar surfaces is investigated by means of Monte Carlo simulations. The effect of image forces stemming from the dielectric discontinuity at the substrate interface is considered. The influence, at fixed polyelectrolyte volume fraction, of chain length and surface-charge density is also considered. A detailed structural study, including monomer and fluid charge distributions, is provided. It is demonstrated that image forces can considerably reduce the degree of polyelectrolyte adsorption and concomitantly inhibit the charge inversion of the substrate by polyelectrolytes.Comment: 19 pages - 7 eps figs - RevTex 4 - submitted for publicatio

Good Oral Health and Diet

An unhealthy diet has been implicated as risk factors for several chronic diseases that are known to be associated with oral diseases. Studies investigating the relationship between oral diseases and diet are limited. Therefore, this study was conducted to describe the relationship between healthy eating habits and oral health status. The dentistry has an important role in the diagnosis of oral diseases correlated with diet. Consistent nutrition guidelines are essential to improve health. A poor diet was significantly associated with increased odds of oral disease. Dietary advice for the prevention of oral diseases has to be a part of routine patient education practices. Inconsistencies in dietary advice may be linked to inadequate training of professionals. Literature suggests that the nutrition training of dentists and oral health training of dietitians and nutritionists is limited

Risk of Periodontal Disease: Is there a Correlation with the Type of Antihypertensive Medication?

Introduction: The purpose of this study was to evaluate the effects of long-term oral antihypertensive treatment using centrally acting sympatho-inhibitory drugs (clonidine) and beta-blockers (metoprolol) on capillary microcirculation in the labial and periodontal mucosa. Methods: Sixty subjects were recruited for the study: 20 patients affected by hypertension in treatment with centrally-acting sympatho-inhibitory drugs (64.28 ± 11.78 years); 20 patients in treatment with beta-blockers (62.03 ± 9.84 years) and 20 healthy subjects (62.06 ± 6.72 years). We use the videocapillaroscopic technique to evaluate in vivo the microcirculation of the labial mucosa corresponding to the lower lip and of the periodontal mucosa corresponding to the central superior incisor. Results: Capillaroscopy revealed a significant increase in the length, diameter, tortuousity and density (P <0.05) of capillaries in patients affected by hypertension in treatment with centrally acting sympatho-inhibitory drugs, while beta-blockers had a lower effect on the labial and periodontal microcirculation compared to the healthy population. Conclusions: The capillaroscopic has revealed substantial modifications of the oral microcirculatory pattern in hypertensive patients in treatment with centrally-acting sympatho-inhibitory drugs than with beta-blockers. Keywords: Hypertension, antihypertensive drug, oral videocapillaroscopy

Perturbative Treatment of the Evolution Operator Associated with Raman Couplings

A novel perturbative treatment of the time evolution operator of a quantum system is applied to the model describing a Raman-driven trapped ion in order to obtain a suitable 'effective model'. It is shown that the associated effective Hamiltonian describes the system dynamics up to a certain transformation which may be interpreted as a 'dynamical dressing' of the effective model

On the age of the magnetically active WW Psa and TX Psa members of the beta Pictoris association

There are a variety of different techniques available to estimate the ages of pre-main-sequence stars. Components of physical pairs, thanks to their strict coevality and the mass difference, such as the binary system analysed in this paper, are best suited to test the effectiveness of these different techniques. We consider the system WW Psa + TX Psa whose membership of the 25-Myr beta Pictoris association has been well established by earlier works. We investigate which age dating technique provides the best agreement between the age of the system and that of the association. We have photometrically monitored WW Psa and TX Psa and measured their rotation periods as P = 2.37d and P = 1.086d, respectively. We have retrieved from the literature their Li equivalent widths and measured their effective temperatures and luminosities. We investigate whether the ages of these stars derived using three independent techniques are consistent with the age of the beta Pictoris association. We find that the rotation periods and the Li contents of both stars are consistent with the distribution of other bona fide members of the cluster. On the contrary, the isochronal fitting provides similar ages for both stars, but a factor of about four younger than the quoted age of the association, or about 30% younger when the effects of magnetic fields are included. We explore the origin of the discrepant age inferred from isochronal fitting, including the possibilities that either the two components may be unresolved binaries or that the basic stellar parameters of both components are altered by enhanced magnetic activity. The latter is found to be the more reasonable cause, suggesting that age estimates based on the Li content is more reliable than isochronal fitting for pre-main-sequence stars with pronounced magnetic activity.Comment: Accepted by Astronomy and Astrophysics on December 13, 2016. 13 pages and 11 figure