Multi-Qubit Entangled State Analyzer Based On The Cavity Input-Output Process

As an important information carrier and the physical resource, quantum en-tangled state has been widely used in quantum information processing tasks, where Bell-state measurement and Greenberger-Horne-Zeilinger(GHZ)-state measurement have also been mentioned and used many times. Here, Bell state and GHZ state measurements are actually the orthogonal projection measurement of quantum state. In order to realize the projection measurement of entanglement state, an analyzer is indispensable to distinguish a set of orthogonal complete entanglement state. There-fore, entanglement analyzer is necessary to build, especially for the implementation of nondestructive entangled analyzer is the important tool of quantum computation and quantum communication. At the same time, as an ideal candidate to realize quantum computer, cavity quantum electrodynamics system has shown great ad-vantages in constructing entangled analyzer. Stationary atoms trapped in cavities are qualified to act as storing information qubits, while the photons are suitable for using as flying qubits to connect different cavities in a quantum network. By check-ing the state of photon, we can nondestructively get atomic information. Therefore, it is is very promising to build multi-qubit entanglement state analyzer based on the model of cavity QED.In this paper, we propose a deterministic scheme to realize multi-qubit entangle-ment state analyzer via the cavity input-output process. In the scheme, we construct a multi-qubit parity analyzer and two phase analyzers and show that all the orthog-onal N-atom GHZ states and multi-atom cluster states can be completely identified in a nondestructive way by combining these two kinds of analyzers. The fidelities of analyzers are also calculated, which show that our scheme has a high perfor-mance in the intermediate coupling region. Therefore, our analyzer may be feasible in experiment, and it opens promising perspectives for large-scale quantum-state-measurement-based quantum communication and quantum information processing networks.