Measuring entanglement is a demanding task that usually requires full tomography of a quantum system, involving a number of observables that grows exponentially with the number of parties. Recently, it was suggested that adding a single ancillary qubit would allow for the efficient measurement of concurrence, and indeed any entanglement monotone associated with antilinear operations. Here, we r...

We address the problem of alarm correlation in large distributed systems. The key idea is to make use of the concurrence of events in order to separate and simplify the state estimation in a faulty system. Petri nets and their causality semantics are used to model concurrency. Special partially stochastic Petri nets are developed, that establish some kind of equivalence between concurrence and ...

As it is well known, every bipartite 2⊗2 density matrix can be obtained from Bell decompos-able states via local quantum operations and classical communications (LQCC). Using this fact, the Lewenstein-Sanpera decomposition of an arbitrary bipartite 2 ⊗ 2 density matrix has been obtained through LQCC action upon Lewenstein-Sanpera decomposition of Bell decomposable states of 2 ⊗ 2 quantum system...

We study quantum entanglement in a single–level quantum dot in the linear– response regime. The results show, that the maximal quantum value of the conductance 2e2/h not always match the maximal entanglement. The pairwise entanglement between the quantum dot and the nearest atom of the lead is also analyzed by utilizing the Wootters formula for charge and spin degrees of freedom separately. The...

Heralded entanglement between collective excitations in two atomic ensembles is probabilistically generated, stored, and converted to single-photon fields. By way of the concurrence, quantitative characterizations are reported for the scaling behavior of entanglement with excitation probability and for the temporal dynamics of various correlations resulting in the decay of entanglement. A lower...

The concept of local concurrence is used to quantify the entanglement between a single qubit and the remainder of a multiqubit system. For the ground state of the BCS model in the thermodynamic limit the set of local concurrences completely describes the entanglement. As a measure for the entanglement of the full system we investigate the average local concurrence (ALC). We find that the ALC sa...

We present a study of the entanglement of formation for one-dimensional magnetic systems with defects. The concurrence was used as a measure of entanglement. Rather than locating the impurity at one site in the chain, there is a Gaussian distribution of disorder near a particular location. We demonstrate that the entanglement can be tuned by varying the strength of the external magnetic field a...

The Lewenstein-Sanpera decomposition for a generic two-qubit density matrix is obtained by using Wootters’s basis. It is shown that the average concurrence of the decomposition is equal to the concurrence of the state. It is also shown that all the entanglement content of the state is concentrated in the Wootters’s state |x1〉 associated with the largest eigenvalue λ1 of the Hermitian matrix √√ ...

The class of nearly balanced incomplete block designs with concurrence range l, or NBBD(l), is defined. This extends previous notions of “most balanced” designs to cover settings where off-diagonal entries of the concurrence matrix must differ by a positive integer l ≥ 2. Sufficient conditions are found for optimality of NBBD(2)’s under type-1 criteria, then used to establish Aand D-optimality ...