Four-Photon Cluster-State Analyzer Based On Cross-Kerr Nonlinearity

In quantum information processing, in order to realize the orthogonal projec-tion measurement of quantum state, it necessary to build entanglement analyzer, for example, Bell state and GHZ state entanglement analyzer have also been men-tioned and used. For the physical implementation of quantum information, optical system as the possible candidates for engineering quantum information task, has always attract much attention and has been widely studied. In optical system, the robustness and the characteristic of easy to be transmitted make photon ideal quan-tum information carrier. Because of achieving optical quantum information task by using linear optical elements. So, qubit is usually encoded on the vertical and hor-izontal polarization states of linearly polarized light. Then, via cross-Kerr medium induces interaction between the photons in probe mode and signal mode by cross phase modulation, so deterministic optical quantum information processing task is feasible.In this dissertation, the main research contents are following:We propose a method to construct a four-photon cluster-state analyzer based on cross-Kerr non-linearity combined with linear optics elements. In the scheme, we first employ a two-qubit parity gate to construct a four-qubit parity gate and show that all sixteen orthogonal four-qubit clusters states can be divided into four groups. Then, we apply a controlled phase gate (CPG) from only giant cross-Kerr nonlinearity and linear optics elements, and once again using a four-qubit parity gate to implement a four-photon cluster-state analyzer. Then, based on this cluster-state analyzer, a four-bit quantum dense coding scheme could be achieved. So, the scheme is signif-icant for large-scale quantum communication and quantum information processing networks. In addition, the scheme is feasible and deterministic under the current experimental conditions.