REMOTE INFORMATION CONCENTRATION VIA FOUR-PARTICLE CLUSTER STATE AND BY POSITIVE OPERATOR-VALUE MEASUREMENT

By using a proper positive operator-valued measure (POVM), we present two new schemes for remote information concentration via four-particle cluster state. It is demonstrated that by employing a maximally entangled (respectively, nonmaximally entangled) four-particle cluster state as the quantum channel, quantum information initially and generally (respectively, specially) distributed in three spatially separated qubits can be remotely and probabilistically concentrated back to a single qubit without performing any global operations. Moreover, the total success probabilities of these two protocols are also worked out. It is more easier to realize experimentally by POVM than by projective measurement.