Long-distance entanglement between two inserted probes in XX chain

In this poster, we study ground state entanglement between two probes at the ends of an isotropic XY chain that coupled by chain by a different coupling constant with respect to the chain. We found that for each length there is a critical coupling constant that before it the concurrence becomes non-vanishing. Also we found that for all lengths of chain can be find a function for concurrence in terms of coupling constant in the scale of critical coupling constant. Also we find the behavior of critical coupling constant for large lengths of chain.