The Greenberger–Horne–Zeilinger (GHZ) states1 play a significant role in fundamental tests of quantum mechanics2 and are one of the central resources of quantum-enhanced high-precision metrology3, fault-tolerant quantum computing4 and distributed quantum networks5. However, in a noisy environment, entanglement becomes fragile as the particle number increases6, 7, 8. Recently, a concatenated GHZ (C-GHZ) state, which retains the advantages of conventional GHZ states but is more robust in a noisy environment, was proposed9. Here, we experimentally prepare a three-logical-qubit C-GHZ state. By characterizing the dynamics of entanglement quality of the C-GHZ state under simple collective noise, we demonstrate that the C-GHZ state is more robust than the conventional GHZ state. Our work provides an essential tool for quantum-enhanced measurement and enables a new route to prepare and manipulate macroscopic entanglement. Our result is also useful for linear-optical quantum computation schemes whose building blocks are GHZ-type states.
At a glance
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