Introduction to Localizable Entanglement

Abbaas Sabour, Fereydoon Khazali, Soghra Ghanavati

In this study, we have addressed an ambiguity in the concept of localizable entanglement (LE) introduced by Verstraete et al in 2004. By doing so, we have proposed and explored a unique form of this entanglement, called new localizable entanglement (NLE). We have shown that NLE is always less than or equal to LE. Additionally, we have demonstrated that for systems with three components, NLE does not differ significantly from LE. However, when the number of components increases to four, there is a possibility of significant differences between the two methods. Furthermore, as the number of components increases further, this difference becomes slightly more pronounced. It appears that the classical correlation, which is the lower bound for LE, is also a lower bound for NLE.

Damian Markham

Ratul Banerjee, Amit Kumar Pal, Aditi Sen

We investigate the patterns in distributions of localizable entanglement over a pair of qubits for random multiqubit pure states. We observe that the mean of localizable entanglement increases gradually with increasing the number of qubits of random pure states while the standard deviation of the distribution decreases. The effects on the distributions, when the random pure multiqubit states are subjected to local as well as global noisy channels, are also investigated. Unlike the noiseless scenario, the average value of the localizable entanglement remains almost constant with the increase in the number of parties for a fixed value of noise parameter. We also find that the maximum strength of noise under which entanglement survives can be independent of the localizable entanglement content of the initial random pure states.

Martin Bodo Plenio, S. Virmani

Jordi Tura i Brugués

Lorenzo Campos Venuti, M. Roncaglia

We study the relation between the recently defined localizable entanglement and generalized correlations in quantum spin systems. Differently from the current belief, the localizable entanglement is always given by the average of a generalized string. Using symmetry arguments we show that in most spin-1/2 and spin-1 systems the localizable entanglement reduces to the spin-spin or string correlations, respectively. We prove that a general class of spin-1 systems, which includes the Heisenberg model, can be used as a perfect quantum channel. These conclusions are obtained in analytic form and confirm some results found previously on numerical grounds.