Experimental realization of a concatenated Greenberger–Horne–Zeilinger state for macroscopic quantum superpositions

With the help of two photonic controlled-NOT gates, a three-logical-qubit concatenated Greenberger–Horne–Zeilinger (C-GHZ) state encoded by a six-photon graph state is experimentally created. Observation of the dynamics of distillability evolving under a collective noisy environment revealed that the C-GHZ state is more robust than the conventional GHZ state.

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