  We present a scheme for the multi-electron Greenberger-Horne-Zeilinger (GHZ)
state analyzer, resorting to an interface between the polarization of a probe
photon and the spin of an electron in a quantum dot embedded in a microcavity.
All the multi-spin GHZ states can be completely discriminated by using
single-photon detectors and linear optical elements. Our scheme has some
features. First, it is a complete GHZ-state analyzer for multi-electron spin
systems. Second, the initial entangled states remain after being identified and
they can be used for a successive task. Third, the electron qubits are static
and the photons play a role of a medium for information transfer, which has a
good application in quantum repeater in which the electron qubits are used to
store the information and the photon qubits are used to transfer the
information between others.
