Entanglement Swapping and Concentration in Multi-Pair Bose--Einstein Condensates

We propose a scheme of entanglement swapping and concentration in a system consisting of multi-pair entangled trapped Bose--Einstein condensates (BECs). In this scheme, entanglement swapping is accomplished by using interference-pattern joint measurements and detecting the total number of condensed atoms leaking out of relevant traps while entanglement concentration is realized by controlling inter-atomic nonlinear and tunnelling interactions. Three- and four-pair BEC schemes are investigated in detail. It is found that with the increasing number of the entangled pairs, the region of entanglement concentration is broadened and the amount of concentrated entanglement is enhanced.