Figure 2
From: Entanglement concentration for arbitrary four-particle linear cluster states
Schematic drawing of ECP for a four-particle cluster state with ancillary particles. PCD means the “parity checking device” which distinguishes the parity between particle i and ancillary particle i′ using cross-Kerr nonlinearity. PBS i represents a polarizing beam splitter, which transmits the particle in the horizontal polarization |H〉 and reflects the particle in the vertical polarization |V〉. R i represents a wave plate which represents a Hadamard operation on the ancillary single particle.
