Nondestructive N-atom Greenberger-Horne-Zeilinger state analyzer via the cavity input-output process

We propose a deterministic scheme to realize N-atom Greenberger-Horne-Zeilinger (GHZ) state analyzer based on the cavity input-output process. In the scheme, we construct a two-qubit parity analyzer and a GHZ-state phase analyzer and show that all the N-atom GHZ states can be completely identified in a nondestructive way by combining these two kinds of analyzers. The fidelities of our analyzers are also calculated, which show that our scheme has a high performance in theory. The scheme opens promising perspectives for achieving efficient large-scale quantum communication and quantum information processing networks. (C) 2012 Optical Society of America