Remote preparation of three-photon entangled states via single-photon   measurement
  Remote state preparation (RSP) provides an indirect way of manipulating quantum information based on the nonlocal effect of quantum measurement. Although RSP has been demonstrated in recent years to remotely prepare multi-photon states, quantum measurement on the same number of photons was required, i.e., to prepare N-photon states via RSP, quantum measurement on the other N-photons was required, hence significantly limiting practicality and applicability of RSP. Here we report the first experimental demonstration of remote preparation of three-photon entangled states by measuring only a single-photon entangled with the three photons. We further generalize our protocol to prepare multi-photon entangled states with arbitrary photon number and purity via single-photon measurement. As our RSP scheme relies on the nonlinearity induced by single-photon measurement, it enables quantum state engineering of multi-photon entangled states beyond the linear optical limit. Our results are expected to have significant impacts on quantum metrology and quantum information processing. 
Young-Sik Ra, Hyang-Tag Lim, Yoon-Ho Kim
quant-ph