Response to defects in multi- and bipartite entanglement of isotropic quantum spin networks

TL;DR

This paper analyzes how isotropic quantum spin networks maintain entanglement despite defects, showing they can sustain multisite entanglement and exhibit bipartite entanglement at moderate ranges, which is crucial for scalable quantum communication.

Contribution

It provides an analytical proof that quantum spin networks with defects can preserve genuine multisite entanglement and exhibit bipartite entanglement, enhancing robustness in quantum networks.

Findings

Networks sustain multisite entanglement despite defects.

Finite defects can induce moderate-range bipartite entanglement.

Entanglement robustness is analytically demonstrated using quantum information theory.

Abstract

Quantum networks are an integral component in performing efficient computation and communication tasks that are not accessible using classical systems. A key aspect in designing an effective and scalable quantum network is generating entanglement between its nodes, which is robust against defects in the network. We consider an isotropic quantum network of spin-1/2 particles with a finite fraction of defects, where the corresponding wave function of the network is rotationally invariant under the action of local unitaries, and we show that any reduced density matrix also remains unaltered under the local actions. By using quantum information-theoretic concepts like strong subadditivity of von Neumann entropy and approximate quantum telecloning, we prove analytically that in the presence of defects, caused by loss of a finite fraction of spins, the network sustains genuine multisite entanglement, and at the same time may exhibit finite moderate-range bipartite entanglement, in contrast to the network with no defects.