Counting Classical Nodes in Quantum Networks

He Lu, Chien Ying Huang, Zheng Da Li, Xu Fei Yin, Rui Zhang, Teh Lu Liao, Yu Ao Chen, Che Ming Li, Jian Wei Pan

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Quantum networks illustrate the use of connected nodes of quantum systems as the backbone of distributed quantum information processing. When the network nodes are entangled in graph states, such a quantum platform is indispensable to almost all the existing distributed quantum tasks. Unfortunately, real networks unavoidably suffer from noise and technical restrictions, making nodes transit from quantum to classical at worst. Here, we introduce a figure of merit in terms of the number of classical nodes for quantum networks in arbitrary graph states. Such a network property is revealed by exploiting a novel Einstein-Podolsky-Rosen steerability. Experimentally, we demonstrate photonic quantum networks of nq quantum nodes and nc classical nodes with nq up to 6 and nc up to 18 using spontaneous parametric down-conversion entanglement sources. We show that the proposed method is faithful in quantifying the classical defects in prepared multiphoton quantum networks. Our results provide novel identification of generic quantum networks and nonclassical correlations in graph states.

Original languageEnglish
Article number180503
JournalPhysical review letters
Issue number18
Publication statusPublished - 2020 May 8

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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