Sensitivity of Measurement-Based Purification Processes to Inner Interactions

The sensitivity of a repeated measurement-based purification scheme to additional undesired couplings is analyzed, focusing on the very simple and archetypical system consisting of two two-level systems interacting with a repeatedly measured one. Several regimes are considered and in the strong coupling (i.e., when the coupling constant of the undesired interaction is very large) the occurrence of a quantum Zeno effect is proven to dramatically jeopardize the efficiency of the purification process.Comment: 12 pages, 6 figure

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

Revealing non-classical behaviours in the oscillatory motion of a trapped ion

The possibility of revealing non-classical behaviours in the dynamics of a trapped ion via measurements of the mean value of suitable operators is reported. In particular we focus on the manifestation known as `` Parity Effect\rq\rq which may be observed \emph{directly measuring} the expectation value of an appropriate correlation operator. The experimental feasibility of our proposal is discussed.Comment: 5 pages, 2 figure

Synchronizing Quantum Harmonic Oscillators through Two-Level Systems

Two oscillators coupled to a two-level system which in turn is coupled to an infinite number of oscillators (reservoir) are considered, bringing to light the occurrence of synchronization. A detailed analysis clarifies the physical mechanism that forces the system to oscillate at a single frequency with a predictable and tunable phase difference. Finally, the scheme is generalized to the case of $N$ oscillators and $M(<N)$ two-level systems.Comment: 9 pages, 3 figure

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

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

Speeding up antidynamical Casimir effect with nonstationary qutrits

The antidynamical Casimir effect (ADCE) is a term coined to designate the coherent annihilation of excitations due to resonant external perturbation of system parameters, allowing for extraction of quantum work from nonvacuum states of some field. Originally proposed for a two-level atom (qubit) coupled to a single cavity mode in the context of nonstationary quantum Rabi model, it suffered from very low transition rate and correspondingly narrow resonance linewidth. In this paper we show analytically and numerically that the ADCE rate can be increased by at least one order of magnitude by replacing the qubit by an artificial three-level atom (qutrit) in a properly chosen configuration. For the cavity thermal state we demonstrate that the dynamics of the average photon number and atomic excitation is completely different from the qubit's case, while the behavior of the total number of excitations is qualitatively similar yet significantly faster.Comment: 9 pages, 4 figure

Teachers’ Perspectives on Year Two Implementation of a Kindergarten Readiness Assessment

In this study we examined teachers’ perspectives regarding the second year of implementing a Kindergarten Readiness Assessment (KRA). Using a mixed-methods approach, we focused on the administration process, the perceived benefits of the assessment, and how teachers used the assessment to inform instruction. We also investigated whether these differed by teacher and district characteristics and how KRA experiences were different in the second year of implementation. Research Findings: Teachers generally did not view the KRA as beneficial for instruction or for students, reporting administration difficulties, inadequate KRA content, and limited utility of KRA data for supporting instruction as ongoing barriers to KRA use. Although the administration process seemed to be easier in the second year, teachers still reported it as burdensome, cutting into important beginning of kindergarten activities. Notably, teacher training and experience were associated with perceptions. Practice or Policy: Reasons for perceived lack of utility have important implications for future KRA design and implementation. These include better integration of KRAs into existing assessment systems, recognizing the added burden of KRAs to teachers (particularly at the beginning of kindergarten), and the role that additional training may have in supporting use of KRAs at the local level