We present a generalization of entanglement based on the idea that entanglement is relative to a distinguished subspace of observables rather than a distinguished subsystem decomposition. A pure quantum state is entangled relative to such a subspace if its expectations are a proper mixture of those of other states. Many information-theoretic aspects of entanglement can be extended to this obser...

We use a Heisenberg spin-1/2 chain to investigate how chaos and localization may affect the entanglement of pairs of qubits. To measure how much entangled a pair is, we compute its concurrence, which is then analyzed in the delocalized/localized and in the chaotic/non-chaotic regimes. Our results indicate that chaos reduces entanglement and that entanglement decreases in the region of strong lo...

We revise the geometric measure of entanglement (GME). The revised geometric measure of entanglement (RGME) is an entanglement monotone. Some useful inequalities about RGME are deduced. As the RGME’s application, the twoparameter class of states in 2⊗ n quantum system, the two particles high dimensional maximally entangled mixed state, the isotropic state including n-particle d-level case and t...

A Poisson model for entanglement optimization in quantum repeater networks is defined in this paper. The nature-inspired multiobjective optimization framework fuses the fundamental concepts of quantum Shannon theory with the theory of evolutionary algorithms. The optimization model aims to maximize the entanglement fidelity and relative entropy of entanglement for all entangled connections of t...

Quantum mechanics has many counter-intuitive consequences which contradict our intuition which is based on classical physics. Here we discuss a special aspect of quantum mechanics, namely the possibility of entanglement between two or more particles. We will establish the basic properties of entanglement using quantum state teleportation. These principles will then allow us to formulate quantit...

We discuss how to characterize entanglement sources with finite sets of measurements. The measurements do not have to be tomographically complete and may consist of POVMs rather than von Neumann measurements. Our method yields a probability that the source generates an entangled state as well as estimates of any desired calculable entanglement measures, including their error bars. We apply two ...

Entanglement which originates from a pair of non-interacting qubits by means of entanglement swapping is discussed when dephasing mechanisms are present. Then, the exact reduced dynamics can be evaluated for two pairs of independent qubits which each are coupled to their own bosonic environment. Each of two pairs of qubits is initially maximally entangled. The conditions for the entanglement su...

Consider the dynamics of a two-qubit entangled system in the decoherence environment, we investigate the stability of pairwise entanglement under decoherence. We find that for different decoherence models, there exist some special class of entangled states of which the pairwise entanglement is the most stable. The lifetime of the entanglement in these states is larger than other states with the...

We review some recently established connections between the mathematics of black hole entropy in string theory and that of multipartite entanglement in quantum information theory. In the case of N = 2 black holes and the entanglement of three qubits, the quartic [SL(2)] 3 invariant, Cayley's hyperdeterminant, provides both the black hole entropy and the measure of tripartite entanglement. In th...

In this paper the the effect of Dzyaloshinskii-Moriya interaction and anisotropy on the Entangle-ment of Heisenberg model has been studied. While the anisotropy suppress the entanglement due to favoring of the alignment of spins, the DM interaction restore the spoiled entanglement via the introduction of the quantum fluctuations. Thermodynamic limit of the model and emerging of non-analytic beh...