Quantum Phase Transitions and Heat Capacity in a two-atoms Bose-Hubbard Model

We show that a two-atoms Bose-Hubbard model exhibits three different phases in the behavior of thermal entanglement in its parameter space. These phases are demonstrated to be traceable back to the existence of quantum phase transitions in the same system. Significant similarities between the behaviors of thermal entanglement and heat capacity in the parameter space are brought to light thus allowing to interpret the occurrence and the meaning of all these three phases.Comment: 6 pages, 3 figure

Quantum thermal machines with single nonequilibrium environments

We propose a scheme for a quantum thermal machine made by atoms interacting with a single non-equilibrium electromagnetic field. The field is produced by a simple configuration of macroscopic objects held at thermal equilibrium at different temperatures. We show that these machines can deliver all thermodynamic tasks (cooling, heating and population inversion), and this by establishing quantum coherence with the body on which they act. Remarkably, this system allows to reach efficiencies at maximum power very close to the Carnot limit, much more than in existing models. Our findings offer a new paradigm for efficient quantum energy flux management, and can be relevant for both experimental and technological purposes.Comment: 10 pages, 6 figure

Thermally-activated non-local amplification in quantum energy transport

We study energy-transport efficiency in light-harvesting planar and 3D complexes of two-level atomic quantum systems, embedded in a common thermal blackbody radiation. We show that the collective non-local dissipation induced by the thermal bath plays a fundamental role in energy transport. It gives rise to a dramatic enhancement of the energy-transport efficiency, which may largely overcome $100\%$. This effect, which improves the understanding of transport phenomena in experimentally relevant complexes, suggests a particularly promising mechanism for quantum energy management.Comment: 7 pages, 4 figures. New version in which the RP line of Figure 1 has been amended with the correct parameter

Heat Capacity and Entanglement Measure in a simple two-qubit model

A simple two-qubit model showing Quantum Phase Transitions as a consequence of ground state level crossings is studied in detail. Using the Concurrence of the system as an entanglement measure and heat capacity as a marker of thermodynamical properties, an analytical expression giving the latter in terms of the former is obtained. A protocol allowing an experimental measure of entanglement is then presented and compared with a related proposal recently reported by Wie\'sniak, Vedral and BruknerComment: 7 pages, 3 figure

Distributed thermal tasks on many-body systems through a single quantum machine

We propose a configuration of a single three-level quantum emitter embedded in a non-equilibrium steady electromagnetic environment, able to stabilize and control the local temperatures of a target system it interacts with, consisting of a collection of coupled two-level systems. The temperatures are induced by dissipative processes only, without the need of further external couplings for each qubit. Moreover, by acting on a set of easily tunable geometric parameters, we demonstrate the possibility to manipulate and tune each qubit temperature independently over a remarkably broad range of values. These findings address one standard problem in quantum-scale thermodynamics, providing a way to induce a desired distribution of temperature among interacting qubits and to protect it from external noise sources.Comment: 6 pages, 5 figure

Fluctuation theorems for non-Markovian quantum processes

Exploiting previous results on Markovian dynamics and fluctuation theorems, we study the consequences of memory effects on single realizations of nonequilibrium processes within an open system approach. The entropy production along single trajectories for forward and backward processes is obtained with the help of a recently proposed classical-like non-Markovian stochastic unravelling, which is demonstrated to lead to a correction of the standard entropic fluctuation theorem. This correction is interpreted as resulting from the interplay between the information extracted from the system through measurements and the flow of information from the environment to the open system: Due to memory effects single realizations of a dynamical process are no longer independent, and their correlations fundamentally affect the behavior of entropy fluctuations.Comment: 7 pages, 1 figur

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

Reality of counseling in pediatric audiology clinical practice

The overwhelming nature of hearing loss identification often causes families to experience grief and confusion. Children as young as nine months old with severe hearing loss have the option to undergo cochlear implantation (CI) surgery with the hopes of restoring normal hearing. Pediatric audiologists accompany families through the identification of hearing loss and the learning process that coincides with this surgery. Despite knowledge that parents of children with communication disabilities will experience a sense of loss and have moderate to severe cyclic emotional reactions, little is known about how audiologists manage the emotional needs of families, if they feel prepared to do so, or if they encounter opportunities to do so in clinical practice. The purpose of this study was to assess the reality of pediatric audiology clinical practice, specifically the counseling that pediatric audiologists provide to parents. Participants were audiologists who provide CI and hearing aid services to pediatric patients in various health service settings, such as hospitals, speech-language clinics or ear-nose-throat clinics. Audiologists reported high confidence in every topic except for a handful, such as communicating with parents in the depression stage of the grief cycle. Most audiologists received a counseling course as a part of their graduate education in audiology, however 61% of counseling courses did not involve role-play experiences and can be considered ineffective courses. A linear regression revealed a significant relationship between an audiologist’s confidence in providing emotional support in initial appointments and the percent of pediatric patients an audiologist sees in their average patient load (b= .011, and p = .001). Years of experience and completion of counseling coursework did not predict confidence in providing personal adjustment counseling. 77% of audiologists agreed that personal-adjustment counseling is within the scope of audiology, but only 61% of audiologists reported that they have the necessary skills to provide adequate personal-adjustment counseling

Tomographic approach to the violation of Bell's inequalities for quantum states of two qutrits

The tomographic method is employed to investigate the presence of quantum correlations in two classes of parameter-dependent states of two qutrits. The violation of some Bell's inequalities in a wide domain of the parameter space is shown. A comparison between the tomographic approach and a recent method elaborated by Wu, Poulsen and Molmer shows the better adequacy of the former method with respect to the latter one.Comment: 9 pages, 4 figure