We exactly evaluate the entanglement of a six vertex and a nine vertex graph states which correspond to non ”twocolorable” graphs. The upper bound of entanglement for five vertices ring graph state is improved to 2.9275, less than upper bound determined by LOCC. An upper bound of entanglement is proposed based on the definition of graph state. PACS number(s): 03.67.Mn, 03.65.Ud, Keyword(s):grap...

We study the entanglement properties of random pure stabilizer states in spin1 2 particles. We obtain a compact and exact expression for the probability distribution of the entanglement values across any bipartite cut. This allows for exact derivations of the average entanglement and the degree of concentration of measure around this average. We also give simple bounds on these quantities. We f...

The dynamical properties of quantum entanglement in two three-level trapped ions interacting with a laser field are studied in terms of the negative eigenvalues of the partial transposition of the density operator. In contrast to the usual belief that destroying the entanglement can be observed due to the environment, it is found that the Stark shift can also produce sudden death of entanglemen...

In this paper, von Neumann entropy is used to study three kinds of bipartite qutrit model, which represent SU(3) strongly correlated model, three-level Lipkin-Meshkov-Glick model, and spin-1 model. The relation between the ground-state entanglement and the quantum phase transition in those models is exhibited and the connection between the entanglement extremes and the symmetries is also discus...

In alternative disentanglement based quantum cryptosystem, classical channel cannot be used when the system is protected by no-cloning principle. But for the similar security criterion , it is discussed that classical channel can be used in alternative entanglement based quantum cryptosystem. A prototype of conventional entanglement based cryptosystem is recovered from alternative entanglement ...

In this Letter we discuss the entanglement near a quantum phase transition by analyzing the properties of the concurrence for a class of exactly solvable models in one dimension. We find that entanglement can be classified in the framework of scaling theory. Further, we reveal a profound difference between classical correlations and the non-local quantum correlation, entanglement: the correlati...

Entanglement is a quantum effect that is not possible in the classical picture. It is here described how an understanding of this effect has evolved to the current state of entanglement theory. The EPR ’paradox’ and Bell’s inequalities are firstly discussed. Then the modern paradigm of entanglement as a resource in e.g. teleportation protocols is described. Finally efforts to quantify this reso...

A strong entanglement monotone, which never increases under local operations and classical communications (LOCC), restricts quantum entanglement manipulation more strongly than the usual monotone since the usual one does not increase on average under LOCC. We propose new strong monotones in mixed-state entanglement manipulation under LOCC. These are related to the decomposability and 1-positivi...

A comparison is made of various searching procedures, based upon different entanglement measures or entanglement indicators, for highly entangled multi-qubits states. In particular, our present results are compared with those recently reported by Brown et al. [J. Phys. A: Math. Gen. 2005 38 1119]. The statistical distribution of entanglement values for the aforementioned multi-qubit systems is ...

The limitations on the production and profitability of entanglement in a harmonic chain under strong driving are considered. We report on the limits of attainable entanglement for a given set of squeezings of the eigenmodes, showing that, the higher the entanglement, the more oscillatory and thus less easy to profit from. We also comment on propagation properties of entanglement, discussing the...