Counting Classical Nodes in Quantum Networks

Abstract

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 $n_q$ quantum nodes and $n_c$ classical nodes with $n_q$ up to 6 and $n_c$ 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.

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Cited by in corpus (8)

• Randomness Certification from Multipartite Quantum Steering for Arbitrary Dimensional Systems
• Quantification of Wigner Negativity Remotely Generated via Einstein-Podolsky-Rosen Steering
• Identifying genuine quantum teleportation
• Experimental distillation of tripartite quantum steering with an optimal local filtering operation
• Witnessing non-Markovianity with Gaussian quantum steering in collision model
• Scalable Determination of Multipartite Entanglement in Quantum Networks
• Scalable multiparty steering based on a single pair of entangled qubits
• Optimal Verification of the Bell State and Greenberger-Horne-Zeilinger States in Untrusted Quantum Networks