Quantum discord amplification of fermionic systems in an accelerated frame

Quantum discord of fermionic systems in the relativistic regime, that is, beyond the single-mode approximation (SMA) is investigated. It is shown that quantum discord is amplified for the fermionic system in non-inertial frames irrespective of the choice of state, region and level of mixedness. This ensures that the phenomenon of amplification can actually happen in the relativistic regime. It is seen that quantum discord converges at infinite acceleration limit, which means that it becomes independent of $q_{R}$ (Unruh modes) beyond SMA. This implies that most of the tensor product structures already used in the literature to compute quantum field correlations in relativistic quantum information cannot give rise to physical results. The dynamics of quantum discord is investigated under amplitude damping, depolarizing and flipping channels. The vanishing behavior of quantum discord is seen for higher level of decoherence in the infinite acceleration limit. The depolarizing channel dominantly affects the fermionic quantum discord as compared to the amplitude damping channel. It means that the depolarizing channel has most destructive influence on the discord of the fermionic systems. Moreover, the effect of environment on the discord is much stronger than that of the acceleration of non-inertial frames.     

SLOCC orbit of rank-deficient two-qubit states: quantum entanglement,quantum discord and EPR steering

We study selected aspects of non-classical correlations of arbitrary states from the stochastic local operations and classical communication orbit of rank-deficient two-qubit states. In particular, we find explicitly entanglement of formation and quantum discord for these states. Moreover, we determine and analyze the Einstein–Podolsky–Rosen steering ellipsoids corresponding to these states.     

Decoherence dynamics of measurement-induced nonlocality and comparison with geometric discord for two qubit systems

We check the decoherence dynamics of Measurement-induced Nonlocality (in short, MIN) and compare it with geometric discord for two qubit systems. There are quantum states, on which the action of dephasing channel cannot destroy MIN in finite or infinite time. We check the additive dynamics of MIN on a qubit state under two independent noise. Geometric discord also follows such additive dynamics like quantum discord. We have further compared non-Markovian evolution of MIN and geometric discord under dephasing and amplitude damping noise for pure state and it shows distinct differences between their dynamics.     

Comparison of quantum discord and relative entropy in some bipartite quantum systems

The study of quantum correlations in high-dimensional bipartite systems is crucial for the development of quantum computing. We propose relative entropy as a distance measure of correlations may be measured by means of the distance from the quantum state to the closest classical–classical state. In particular, we establish relations between relative entropy and quantum discord quantifiers obtained by means of orthogonal projection measurements. We show that for symmetrical X-states density matrices the quantum discord is equal to relative entropy. At the end of paper, various examples of X-states such as two-qubit and qubit–qutrit have been demonstrated.     

The dynamics of local quantum uncertainty and trace distance discord for two-qubit <Emphasis Type="Italic">X</Emphasis> states under decoherence: a comparative study

We employ the concepts of local quantum uncertainty and geometric quantum discord based on the trace norm to investigate the environmental effects on quantum correlations of two bipartite quantum systems. The first one concerns a two-qubit system coupled with two independent bosonic reservoirs. We show that the trace discord exhibits frozen phenomenon contrarily to local quantum uncertainty. The second scenario deals with a two-level system, initially prepared in a separable state, interacting with a quantized electromagnetic radiation. Our results show that there exists an exchange of quantum correlations between the two-level system and its surrounding which is responsible for the revival phenomenon of non-classical correlations.     

Evaluating the value of collaboration systems in collocated teams: A longitudinal analysis

Distributed work structure has increased the importance of group work. Consequently, the usage of collaboration systems that support group work has increased exponentially. However, limited research exists on why collocated group members use collaborative system and how their perceptions about the system change from project initiation to project completion. The study proposes resource management support, coordination support, and evaluation support as key aspects based on which collocated users form beliefs about collaboration system value. Based on technology acceptance model and expectancy disconfirmation theory, we propose a model that examines the evolution of user beliefs from pre to post-adoption stage. Further, we argue that users may engage in different information processing strategies as part of the belief change process. The research model was examined based on longitudinal data collected from student groups working on a software application development project over a three month period. The results show that users deemed all features to be valuable at the pre-adoption stage. However, at the post-adoption stage evaluation support was the only factor that had a direct influence on collaboration system usefulness. While the impact of other support factors was mediated through the confirmation process. Further, users engaged in high information processing in revising their beliefs about collaboration system features, when they experienced a high level of dissonance. On the contrary, a dual information processing approach was visible in the context of support features that required adjustment or update to beliefs from pre to post-adoption stage. The study provides three core areas around which designers can structure collaboration system features to make it more useful. It also provides theoretical insights into the process through which user cognitions about collaboration system value change over time.     

Causal effects in longitudinal studies: Definition and maximum likelihood estimation

Recently, a nonparametric marginal structural model (NPMSM) approach to Causal Inference has been proposed [Neugebauer, R., van der Laan, M., 2006. Nonparametric causal effects based on marginal structural models. J. Statist. Plann. Inference (in press), 〈www http://www.sciencedirect.com/science/journal/03783758〉.] as an appealing practical alternative to the original parametric MSM (PMSM) approach introduced by Robins [Robins, J., 1998a. Marginal structural models. In: 1997 Proceedings of the American Statistical Association, American Statistical Association, Alexandria, VA, pp. 1-10]. The new MSM-based causal inference methodology generalizes the concept of causal effects: the proposed nonparametric causal effects are interpreted as summary measures of the causal effects defined with PMSMs. In addition, causal inference with NPMSM does not rely on the assumed correct specification of a parametric MSM but instead defines causal effects based on a user-specified working causal model which can be willingly misspecified. The NPMSM approach was developed for studies with point treatment data or with longitudinal data where the outcome is not time-dependent (typically collected at the end of data collection). In this paper, we generalize this approach to longitudinal studies where the outcome is time-dependent, i.e. collected throughout the span of the studies, and address the subsequent estimation inconsistency which could easily arise from a hasty generalization of the algorithm for maximum likelihood estimation. More generally, we provide an overview of the multiple causal effect representations which have been developed based on MSMs in longitudinal studies.     

The reciprocal effects of social network site use and the disposition for self-disclosure: A longitudinal study

Since the advent of social network sites (SNSs), scholars have critically discussed the psychological and societal implication of online self-disclosure. Does Facebook change our willingness to disclose personal information? The present study proposes that the use of SNSs and the psychological disposition for self-disclosure interact reciprocally: Individuals with a stronger disposition show a higher tendency to use SNSs (selection effect). At the same time, frequent SNS use increases the wish to self-disclose online, because self-disclosing behaviors are reinforced through social capital within the SNS environment (socialization effect). In a longitudinal panel study, 488 users of SNSs were surveyed twice in a 6 months interval. Data were analyzed using structure equation modeling. The proposed reciprocal effects of SNS activities and self-disclosure were supported by the data: The disposition for online self-disclosure had a positive longitudinal effect on SNS use which in turn positively influenced the disposition for online self-disclosure. Both effects were moderated by the amount of social capital users received as a consequence of their SNS use.     

Relationship between the field local quadrature and the quantum discord of a photon-added correlated channel under the influence of scattering and phase fluctuation noise

We study quantum correlations and discord in a bipartite continuous variable hybrid system formed by linear combinations of coherent states \(\mathinner {|{\alpha }\rangle }\) and single photon-added coherent states of the form \(\mathinner {|{\psi }\rangle }_{\text {dp(pa)}}= \mathcal {N}/\sqrt{2} (\hat{a}^\dagger \mathinner {|{\alpha }\rangle }_a\mathinner {|{\alpha }\rangle }_b \pm \hat{b}^\dagger \mathinner {|{\alpha }\rangle }_a\mathinner {|{\alpha }\rangle }_b)\). We stablish a relationship between the quantum discord with a local observable (the quadrature variance for one subsystem) under the influence of scattering and phase fluctuation noise. For the pure states the quantum correlations are characterized by means of measurement induced disturbance (MID) with simultaneous quadrature measurements. In a scenario where homodyne conditional measurements are available we show that the MID provides an easy way to select optimal phases to obtain information of the maximal correlations in the channels. The quantum correlations of these entangled states with channel losses are quantitatively characterized with the quantum discord (QD) with a displaced qubit projector. We observe that as scattering increases, QD decreases monotonically. At the same time for the state \(\mathinner {|{\psi }\rangle }_{\text {dp}}\), QD is more resistant to high phase fluctuations when the average photon number \(n_0\) is bigger than zero, but if phase fluctuations are low, QD is more resistant if \(n_0=0\). For the dp model with scattering, we obtain an analytical expression of the QD as a function of the observable quadrature variance in a local subsystem. This relation allows us to have a way to obtain the degree of QD in the channel by just measuring a local property observable such as the quadrature variance. For the other model this relation still exists but is explored numerically. This relation is an important result that allows to identify quantum processing capabilities in terms of just local observables.     

On the non-conservatism of a novel LMI relaxation for robust analysis of polytopic systems

It is known that robust analysis of polytopic systems, i.e. linear system with polytopic state space uncertainty, is a difficult problem. Recently we have proposed for this problem, in both continuous-time and discrete-time cases, the use of homogeneous polynomially parameter-dependent quadratic Lyapunov functions (HPD-QLFs) by introducing a novel LMI relaxation which provides a sufficient condition via a convex optimization without requiring the use of auxiliary multipliers of unknown degree. In this paper we show that this condition is not only sufficient but it is also necessary.     

Trading quantization precision for update rates for systems with limited communication in the uplink channel

In many situations, control applications have to exchange information through limited bandwidth communication channels, which affect their behavior. For that reason, there is a strong need for methods that maximize the relevancy of the exchanged control signals. In general, increasing control signals’ update frequency improves the disturbance rejection abilities whereas increasing their quantization precision improves the steady state performance. However, when the bandwidth is limited, increasing the update frequency necessitates the reduction of the quantization precision and vice versa. Motivated by these observations, and focusing on the uplink bandwidth limitations, an approach for the dynamical online state feedback assignment of control inputs’ quantization precision and update rate is proposed. This approach, which is based on the model predictive control technique, enables us to choose the update rate and the quantization levels of control signals from a predefined set, in order to optimize the control performance. Practical stability properties of the approach are then studied. Finally, the effectiveness of the proposed method is illustrated on a simulation example.     

Optimal MRP offsetting for assembly systems with stochastic lead times: POQ policy and service level constraint

This study deals with component supply planning in assembly systems, i.e. where several types of components are needed to produce one finished product. The actual component lead times have random deviations, so they can be considered as random variables. MRP approach with Periodic Order Quantity policy is considered. The aim is to find the optimal MRP offsetting. The proposed model and algorithms minimize the sum of the setup and average holding costs for the components, while satisfying a desired service level.     

Multi-objective optimization for inventory control in two-level assembly systems under uncertainty of lead times

Supply planning for two-level assembly systems under lead time uncertainties is considered. It is supposed that the demand for the finished product and its due date are known. The assembly process at each level begins when all necessary components are in inventory. A holding cost at each level appears if some components needed to assemble the same semi-finished product arrive before beginning the assembly at this level. It is assumed also that the component lead time is a random discrete variable. The objective is to find the release dates for the components at level 2 in order to minimize the expected component holding costs and to maximize the customer service level for the finished product. For this new problem, we consider two multi-objective approaches, which are both based on genetic algorithms. They are evaluated with a variety of supply chain settings, and their respective performance is reported and commented. These two heuristics permitted to obtain interesting results within a reasonable computational time.     

Convergence and comparisons of waveform relaxation methods for initial value problems of linearODE systems

In this paper we investigate waveform relaxation (WR) methods for solving initial value problems of linearODE systems. Some sufficient conditions for convergence are proposed. A class ofWR AOR, WR SOR, andWR JOR methods is defined and their convergence is discussed. The asymptotic rates of convergence of two differentWR methods are compared.     

The effects of precueing on vibrotactile reaction times: implications for a guidance device for blind people

Abstract

Reaction times to a vibrotactile display are examined in two experiments which address the issues of secondary task and stimulus preview. Results suggest that although performing a secondary task significantly increases reaction times to a vibrotactile stimulus delivered to the fingers, this can be compensated for by presenting precueing stimuli. The implications of these findings in relation to guidance devices for the blind are discussed.     

Quantum coherence of fermionic systems in noninertial frames beyond the single-mode approximation

In this paper, we investigate the behavior of the quantum coherence for bipartite fermionic systems in noninertial frames beyond the single-mode approximation. It is shown a redistribution of coherence between particle and antiparticle modes, and the behavior in terms of coherence for fermionic systems is convergent in the infinite acceleration limit. We demonstrate that the physical accessible coherence is not always destroyed with the increase in acceleration, which is different from the features of entanglement in the accelerated frame. Besides, we obtain a quantitative relationship about the redistribution of coherence via the \(l_1\)-norm measure. It is worth mentioning that a rotation operation can change the coherence values, since the amount of coherence is related to the selection of reference basis.     

A versatile technology platform for microfluidic handling systems,part II: channel design and technology

Microfluidic devices often require channels of a specific size and shape. These devices are then made in a fabrication process that is often specialized to produce only those (and very similar) channels. As a result, devices requiring channels of different size and shape cannot easily be integrated on the same chip. This paper presents a method to fabricate microfluidic channels in a wide range of shape and size on the same chip by using a slit pattern through which the channels are etched. The fabrication process to fabricate these channels is discussed in detail, and an empirical model is presented to find the optimal slit pattern for a required size and shape. This part of the paper focusses on the channel design and fabrication. Details on the whole fabrication process and optional functionalization of the channels are presented in part I of this paper.     

Bounds for nonpreemptive scheduling of jobs with similar processing times on multiprocessor systems using the LPT-Algorithm

The well-known, NP-complete problem of scheduling a set ofn independent jobs nonpreemptively onm identical parallel processors to minimize the maximum finish time is considered. Let ω₀ be the finish time of an optimal schedule and ω the finish time of a schedule found by the Longest Processing Time (LPT-)heuristic. We will improve the Graham-bound for the LPT-heuristic (ω/ω₀ ≤ 4/3 ? 1/3m) which is tight in general, by considering only jobs with similar processing times.     

Social presence and group attraction: exploring the effects of awareness systems in the home

This paper describes an experimental assessment of affective user benefits that may result from adding peripheral awareness information while remote friends share an activity in a home environment. The experiment has shown that providing awareness information increases the social presence and the group attraction felt by individuals towards remote partners.