  One-way quantum computation based on measurement and multipartite cluster
entanglement offers the ability to perform a variety of unitary operations only
through different choices of measurement bases. Here we present an experimental
study toward demonstrating the controlled-X operation, a two-mode gate, in
which continuous variable (CV) four-partite cluster states of optical modes are
utilized. Two quantum teleportation elements are used for achieving the gate
operation of the quantum state transformation from input target and control
states to output states. By means of the optical cluster state prepared
off-line, the homodyne detection and electronic feeding forward, the
information carried by the input control state is transformed to the output
target state. The presented scheme of the controlled-X operation based on
teleportation can be implemented nonlocally and deterministically. The
distortion of the quantum information resulting from the imperfect cluster
entanglement is estimated with the fidelity.
