Quantum circuits for controlled teleportation of two-particle entanglement via a W state

A protocol for three-party controlled quantum teleportation is discussed. It is shown that an unknown two-particle entanglement can be teleported to any one of two receivers via the only one three-particle W state. We summarize all different unitary transformations performed by the receiver with a concise formula. The quantum circuits for the generalized measurement described by positive operator-valued measure (POVM), which is utilized to probabilistically distinguish the two non-orthogonal states, are explicitly constructed by means of quantum Toffoli gates. The efficient quantum circuits for implementing the teleportation are also provided. (C) 2007 Elsevier B.V. All rights reserved.