We present a nonlocal entanglement concentration scheme for reconstructing
some maximally entangled multipartite states from partially entangled ones by
exploiting cross-Kerr nonlinearities to distinguish the parity of two
polarization photons. Compared with the entanglement concentration schemes
based on two-particle collective unitary evolution, this scheme does not
require the parties to know accurately information about the partially
entangled states--i.e., their coefficients. Moreover, it does not require the
parties to possess sophisticated single-photon detectors, which makes this
protocol feasible with present techniques. By iteration of entanglement
concentration processes, this scheme has a higher efficiency and yield than
those with linear optical elements. All these advantages make this scheme more
efficient and more convenient than others in practical applications.Comment: 7 pages, 4 figures. Physical Review A 77, 062325 (2008