3,818 research outputs found
Guaranteed bounds on the Kullback-Leibler divergence of univariate mixtures using piecewise log-sum-exp inequalities
Information-theoretic measures such as the entropy, cross-entropy and the
Kullback-Leibler divergence between two mixture models is a core primitive in
many signal processing tasks. Since the Kullback-Leibler divergence of mixtures
provably does not admit a closed-form formula, it is in practice either
estimated using costly Monte-Carlo stochastic integration, approximated, or
bounded using various techniques. We present a fast and generic method that
builds algorithmically closed-form lower and upper bounds on the entropy, the
cross-entropy and the Kullback-Leibler divergence of mixtures. We illustrate
the versatile method by reporting on our experiments for approximating the
Kullback-Leibler divergence between univariate exponential mixtures, Gaussian
mixtures, Rayleigh mixtures, and Gamma mixtures.Comment: 20 pages, 3 figure
Thermal entanglement and teleportation in a two-qubit Heisenberg chain with Dzyaloshinski-Moriya anisotropic antisymmetric interaction
Thermal entanglement of a two-qubit Heisenberg chain in presence of the
Dzyaloshinski-Moriya (DM) anisotropic antisymmetric interaction and
entanglement teleportation when using two independent Heisenberg chains as
quantum channel are investigated. It is found that the DM interaction can
excite the entanglement and teleportation fidelity. The output entanglement
increases linearly with increasing value of input one, its dependences on the
temperature, DM interaction and spin coupling constant are given in detail.
Entanglement teleportation will be better realized via antiferromagnetic spin
chain when the DM interaction is turned off and the temperature is low.
However, the introduction of DM interaction can cause the ferromagnetic spin
chain to be a better quantum channel for teleportation. A minimal entanglement
of the thermal state in the model is needed to realize the entanglement
teleportation regardless of antiferromagnetic or ferromagnetic spin chains.Comment: 1 tex;5eps. accepted by Physical Review
Entanglement dynamics of two independent Jaynes-Cummings atoms without rotating-wave approximation
Entanglement evolution of two independent Jaynes-Cummings atoms without
rotating-wave approximation (RWA) is studied by an numerically exact approach.
The previous results in the RWA are essentially modified in the strong coupling
regime (), which has been reached in the recent experiments on the
flux qubit coupled to the LC resonator. For the initial Bell state with
anti-correlated spins, the entanglement sudden death (ESD) is absent in the
RWA, but does appear in the present numerical calculation without RWA.
Aperiodic entanglement evolution in the strong coupling regime is observed. The
strong atom-cavity coupling facilitates the ESD. The sign of detuning play a
essential role in the entanglement evolution for strong coupling, which is
irrelevant in the RWA. An analytical results based on an unitary transformation
are also given, which could not modify the RWA picture essentially. It is
suggested that the activation of the photons may be the origin of the ESD. The
present theoretical results could be applied to artificial atoms realized in
recent experiments.Comment: 16 pages, 8 figure
Putting context into organizational intervention design:Using tailored questionnaires to measure initiatives for worker well-being
Realistic evaluation emphasizes the importance of exploring the mechanisms through which organizational interventions are effected. A well-known mechanism in organizational interventions is the screening process. Standardized questionnaires, in popular use, neither consider individuals’ appraisals of working conditions nor the specific context of the workplace. Screening with items tailored to intervention contexts may overcome the limitations of standardized questionnaires. In the present study, we evaluate an approach to develop a tailored questionnaire to measure employees’ appraisals of their specific working conditions. First, we interviewed 56 employees and 17 managers and, later, developed tailored items focused on the working conditions in a postal service. In follow-up interviews, we explore participants’ experiences with the tailored questionnaire, including the development of initiatives, compared to their previous experiences with the company´s annual attitude survey that used standardized scales. Results indicated that participants felt the tailored questionnaire highlighted issues that had previously been ignored, that initiatives were easier to develop due to its specificity, and that the feedback strategy was useful in prioritizing questionnaires. Overall, it can be concluded that tailored questionnaires may be appropriate for use in organizational intervention research and more broadly that evaluations of organizational interventions need to be contextually grounded
Lower Bounds of Concurrence for Tripartite Quantum Systems
We derive an analytical lower bound for the concurrence of tripartite quantum
mixed states. A functional relation is established relating concurrence and the
generalized partial transpositions.Comment: 10 page
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