Distillation of entanglement between distant systems by repeated measurements on an entanglement mediator

A proposed purification method utilized to yield entangled states between distant systems was discussed. The extracted entangled states among systems that were located at separate places were applied to simple systems to show the potentiality of a measurement-based purification scheme. It was shown that the measurements of a two-level system could distill entangled states from the latter irrespective of the initial states of the two subsystems. It was found that the establishment of entanglement distillation relied on the successive interactions between the systems under consideration and the so-called 'mediator' quantum systems.